%0 Journal Article
%9 Article de recherche
%A Nguyen, Trung-Hien
%A L. Bramerie
%A M. Gay
%A M. Kazdoghli-Lagha
%A C. Peucheret
%A R. Gerzaguet
%A Gorza, Simon-Pierre
%A Louveaux, Jérôme
%A Horlin, François
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Experimental Demonstration of the Trade-off between Chromatic Dispersion and Phase Noise Compensation in Optical FBMC/OQAM Communication Systems
%X Filterbank multicarrier based on offset-quadrature amplitude modulation (FBMC/OQAM) is a promising candidate for optical fiber communication systems, thanks to its better time/frequency confinement compared to other multicarrier modulations. Among linear impairments, the compensation of fiber-induced chromatic dispersion (CD) and laser-induced phase noise (PN) in FBMC/OQAM systems induces a compromise in terms of the number of used subcarriers. Considering a fixed dedicated signal bandwidth, the number of subcarriers is expected to be large enough to allow a better frequency-domain CD compensation. On the other hand, it should be sufficiently small in order for the compensation of common phase error inherent to the PN to work properly. In this paper, we experimentally demonstrate the trade-off between CD and PN compensation that we previously highlighted by simulations. More specifically, considering a 20 GHz FBMC/4–OQAM modulation and an aggregated laser linewidth of about 200 kHz, we show that the maximum transmission distance reaches 3100 km with nearly 512 active subcarriers and 3-tap equalizers, when a maximum 1 dB optical signal-to-noise ratio (OSNR) penalty at a bit-error-rate (BER) of 3.8×10$^{-3}$ can be tolerated. Moreover, we propose and validate a frame structure and an integrated synchronization/channel equalization architecture to implement a standalone demodulation system.
%K Optical fibers
%K Optical filters
%K Receivers
%K Optical transmitters
%K Optical modulation
%K Filterbank multicarrier
%K offset-QAM
%K coherent detection
%K PN estimation
%K CD compensation
%K CFO compensation
%K long-haul communications
%G Anglais
%J Journal of Lightwave Technology
%B Journal of Lightwave Technology
%P 1-1
%D 2019
%@ 0733-8724 (ISSN)
%@ 1558-2213 (e-ISSN)
%* peer-reviewed
%D 2019
%U Handle: http://hdl.handle.net/2078.1/217510
%R 10.1109/JLT.2019.2923763
%0 Journal Article
%9 Article de recherche
%A Gueuning, Quentin
%A Craeye, Christophe
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Sampling rules for an inhomogeneous plane-wave representation of scattered fields
%X Inhomogeneous plane waves (IPWs) based on a linear contour deformation provide an accurate and concise field representation for scattering problems in which source and observation domains are visible within a limited angular sector. Given an error level, we derive closed-form expressions for the truncation limit, the sampling step, and the contour slope that minimize the number of plane waves. A relation is drawn between the required number of plane waves and the degrees of freedom of the field, defined as the minimum number of orthonormal basis functions that represents scattered fields. The sampling rules are then applied to an efficient evaluation of the physical optics radiation integral.
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%V 67
%N 3
%P 1697 - 1708
%D 2019
%@ 0018-926X (ISSN)
%@ 1558-2221 (e-ISSN)
%* peer-reviewed
%D 2019
%U Handle: http://hdl.handle.net/2078.1/217413
%R 10.1109/TAP.2018.2885414
%0 Journal Article
%9 Article de recherche
%A Rottenberg, François
%A Dat, Pham Tien
%A Kanno, Atsuhi
%A Horlin, François
%A Louveaux, Jérôme
%A Yamamoto, Naokastu
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T 2x2 MIMO FBMC-OQAM Signal Transmission over a Seamless Fiber–Wireless System in W-band
%X Offset-QAM-based filterbank multicarrier (FBMC-OQAM) is an attractive modulation candidate to increase the spectral efficiency of radio-over-fiber and fiber--wireless systems. In this paper, we first propose a general framework for MIMO FBMC-OQAM transmission systems, including the description of algorithms for mitigation of the channel impairments. The proposed design is scalable in the number of transmitted streams and flexible as multiple asynchronous users can be accommodated. The proposed system is experimentally validated in a 2x2 MIMO FBMC-OQAM signal over a seamless fiber--wireless in the W-band for the first time. Satisfactory performance is confirmed for a data rate of up to 18 Gb/s in both downlink and uplink directions. Furthermore, algorithms previously proposed by the authors for channel estimation and phase noise compensation are experimentally validated, confirming their effectiveness. Finally, we show that, for a similar error vector magnitude performance, an FBMC-OQAM system can achieve a 25% higher throughput rate than a corresponding orthogonal frequency division multiplexing-based fiber--wireless system.
%K MIMO communication
%K Modulation
%K Channel estimation
%K Transceivers
%K Frequency division multiplexing
%K Wireless communication
%K Synchronization
%K Fiber-wireless convergence
%K radio-over-fiber
%K FBMC-OQAM
%K MIMO
%K Fiber-wireless convergence
%K radio-over-fiber
%K FBMC-OQAM
%K MIMO
%K MIMO communication
%K Modulation
%K Channel estimation
%K Transceivers
%K Frequency division multiplexing
%K Wireless communication
%K Synchronization
%G Anglais
%J IEEE Photonics Journal
%B IEEE Photonics Journal
%V 10
%N 2
%P 1-14
%D 2018
%@ 1943-0655 (e-ISSN)
%* peer-reviewed
%D 2018
%U Handle: http://hdl.handle.net/2078.1/194862
%R 10.1109/JPHOT.2018.2803209
%0 Journal Article
%9 Article de recherche
%A Torrea-Duran, Rodolfo
%A Rosas, Fernando
%A Pollin, Sofie
%A Vandendorpe, Luc
%A Moonen, Marc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T A Multiple-Relay Communication Protocol for Achieving Fairness in Dense Networks
%X Increasing the density of base stations deployment is regarded as a means to satisfy the growing demand of wireless connectivity over a shared bandwidth, however, increasing the disparity in the service received by each user. Fairness can be realized by dynamically allocating resources to users using detailed channel state information at the transmitter (CSIT), which constitutes an expensive overhead, especially, for dense networks. One solution to improve the fairness without CSIT is to introduce spatial diversity through the use of relays in combination with physical-layer network coding (PNC). Most relaying-PNC solutions focus on the particular case of the two-way relay channel or they require additional relays and a large transmission time. In this paper, we propose a multiple-relay communication protocol (MRCP) for achieving fairness in dense networks. It exploits spatial diversity without requiring additional relays since it uses the base stations as relays. Furthermore, MRCP is applicable to an arbitrary number of base stations and users, while keeping a small transmission time. We show that our approach achieves the highest max-min fairness among users and almost full diversity with asymmetric transmissions.
%K ICTM:COMM
%K ICTM:SIGN
%G Anglais
%J IEEE Access
%B IEEE Access
%V 6
%N 1
%P 6740-6754
%D 2018
%@ 2169-3536 (e-ISSN)
%* peer-reviewed
%D 2018
%U Handle: http://hdl.handle.net/2078.1/209301
%R 10.1109/access.2018.2797128
%0 Journal Article
%9 Article de recherche
%A Benedetto, F.
%A Giunta, G.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T A theoretical note on the generalized ML optimality of constant modulus equalizers
%X In this work, we derive the optimum equalizer according to the General Maximum Likelihood (GML) principle and show the optimality of the constant-modulus algorithm (CMA) according to the GML principle. This reported discussion illustrates why CMA works well and hence is so popular. Moreover, we show that the minimization of normalized variance algorithm (MNVA) previously introduced by the authors, as much as the asymptotically equivalent Kurtosis maximization algorithm and “Rayleigh-ness” test criteria, are asymptotically optimum according to the GML criterion.
%K Control and Systems Engineering
%K Signal Processing
%K Electrical and Electronic Engineering
%K Software
%K Computer Vision and Pattern Recognition
%K ICTM:COMM
%K ICTM:SIGN
%G Anglais
%J Signal Processing
%B Signal Processing
%V 143
%P 298-302
%D 2018
%@ 0165-1684 (ISSN)
%@ 0165-1684 (e-ISSN)
%* peer-reviewed
%D 2018
%U Handle: http://hdl.handle.net/2078.1/189858
%R 10.1016/j.sigpro.2017.09.018
%0 Journal Article
%9 Article de recherche
%A Morales-Cespedes, Maximo
%A Paredes-Paredes, Martha Cecilia
%A Garcia Armada, Ana
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Aligning the Light Without Channel State Information for Visible Light Communications
%X The use of light-emitting diodes (LEDs) for ambient illumination leads to visible light communications (VLC) as a promising technology for providing both constant lighting and high-speed wireless services in indoor environments. Since multiple LED sources can be transmitted to several users, this scenario naturally forms a multiple-user multiple-input single-output system. In this sense, transmit precoding (TPC) schemes based on channel state information at the transmitter (CSIT) originally devised for radio-frequency (RF) systems have been proposed for their implementation in VLC. However, beyond providing CSIT or the need for cooperation among transmitters, which also result challenging in RF systems, there are several constraints such as the non-negativity of the transmitted signal or providing constant illumination that hamper the performance of TPC schemes in VLC. Considering these constraints, this paper explores the use of blind interference alignment (BIA) for achieving multiplexing gain without CSIT or cooperation among LED lights. To do that, we devise the concept of reconfigurable photodetector that allows switching among distinct and linearly independent channel responses. Simulation results show that the use of BIA in VLC systems schemes based on the proposed reconfigurable photodetector results suitable for VLC systems.
%K visible light
%G Anglais
%J IEEE Journal on Selected Areas in Communications
%B IEEE Journal on Selected Areas in Communications
%V 36
%N 1
%P 91-105
%D 2018
%@ 0733-8716 (ISSN)
%* peer-reviewed
%D 2018
%U Handle: http://hdl.handle.net/2078.1/209303
%R 10.1109/jsac.2017.2774518
%0 Journal Article
%9 Article de recherche
%A Hanssens, Brecht
%A Plets, David
%A Tanghe, Emmeric
%A Oestges, Claude
%A Gaillot, Davy P.
%A Lienard, Martine
%A Li, Taoyong
%A Steendam, Heidi
%A Martens, Luc
%A Joseph, Wout
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T An Indoor Variance-Based Localization Technique Utilizing the UWB Estimation of Geometrical Propagation Parameters
%X A novel localization framework is presented based on ultra-wideband (UWB) channel sounding, employing a triangulation method using the geometrical properties of propagation paths, such as time delay of arrival, angle of departure, angle of arrival, and their estimated variances. In order to extract these parameters from the UWB sounding data, an extension to the high-resolution RiMAX algorithm was developed, facilitating the analysis of these frequency-dependent multipath parameters. This framework was then tested by performing indoor measurements with a vector network analyzer and virtual antenna arrays.The estimated means and variances of these geometrical parameters were utilized to generate multiple sample sets of input values for our localization framework. Next to that, we consider the existence of multiple possible target locations, which were subsequently clustered using a Kim-Parks algorithm, resulting in a more robust estimation of each target node. Measurements reveal that our newly proposed technique achieves an average accuracy of 0.26, 0.28, and 0.90 m in line-of-sight (LoS), obstructed-LoS, and non-LoS scenarios, respectively, and this with only one single beacon node. Moreover, utilizing the estimated variances of the multipath parameters proved to enhance the location estimation significantly compared to only utilizing their estimated mean values.
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%V 66
%N 5
%P 2522-2533
%D 2018
%@ 0018-926X (ISSN)
%@ 1558-2221 (e-ISSN)
%* peer-reviewed
%D 2018
%U Handle: http://hdl.handle.net/2078.1/204132
%R 10.1109/tap.2018.2810340
%0 Journal Article
%9 Article de recherche
%A Hanssens, Brecht
%A Martínez-Inglés, María-Teresa
%A Tanghe, Emmeric
%A Plets, David
%A Molina-García-Pardo, José-María
%A Oestges, Claude
%A Martens, Luc
%A Joseph, Wout
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Measurement-based analysis of specular and dense multipath components at 94 GHz in an indoor environment
%X In this study, the authors present a measurement-based analysis of the indoor radio channel characteristics of both the specular and dense multipath components [specular part of the channel (SMC) and diffuse part of the channel] at 94 GHz within a 3 GHz bandwidth. On the basis of an investigation of the frequency stationarity of this band, they have selected multiple sub-bands to perform their evaluation. A method is developed that allowed for the estimation of the specular propagation paths, after which the remainder is regarded as the diffuse spectrum. Radio channel characteristics such as the path loss, root-mean-square delay spread, and the SMC ratio have been calculated as a function of transmitter-receiver distance, and in the different sub-bands. On the basis of the diffuse spectrum, the behaviour of the reverberation time is analysed for the first time in the 94 GHz band.
%G Anglais
%J IET Microwaves, Antennas & Propagation
%B IET Microwaves, Antennas & Propagation
%V 12
%N 4
%P 509-515
%D 2018
%@ 1751-8725 (ISSN)
%@ 1751-8733 (e-ISSN)
%* peer-reviewed
%D 2018
%U Handle: http://hdl.handle.net/2078.1/204130
%R 10.1049/iet-map.2017.0553
%0 Journal Article
%9 Article de recherche
%A Miao, Yang
%A Gueuning, Quentin
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Modeling the Phase Correlation of Effective Diffuse Scattering From Surfaces for Radio Propagation Prediction With Antennas at Refined Separation
%X Diffuse scattering (DS), mostly caused by macroscopically rough surfaces, can be modeled by an effective roughness (ER) approach. In the ER approach, the object surface is divided into tiles, and the DS field amplitude associated with each tile is given. Assuming that the transmit antenna (or emitted field) is fixed and the phases associated with different tiles are independent, this paper proposes a phase evolution model based on the relative spatial locations of the receive antenna (Rx) to each tile. The proposed model contains two parts: the deterministic part that depends on the variation of the distance from Rx to tile center, and the correlated random part that depends on the variation of the angle between the Rx and the normal vector of tile. The correlation of the tile field phases resulting from the angular variation is modeled by the exponentially damped cosine correlation function. The proposed phase evolution model is evaluated by being applied to the ER approach to predict the DS component of radio channel transfer function (CTF). The predicted DS-CTF is compared with the reference (simulated data by physical optics and measured data in well-controlled environment) in terms of the spatial autocorrelation as well as the spatial Doppler spectrum.
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%V 66
%N 3
%P 1427-1435
%D 2018
%@ 0018-926X (ISSN)
%@ 1558-2221 (e-ISSN)
%* peer-reviewed
%D 2018
%U Handle: http://hdl.handle.net/2078.1/204127
%R 10.1109/tap.2018.2794372
%0 Journal Article
%9 Article de recherche
%A Doone, Michael G.
%A Cotton, Simon L.
%A Matolak, David W.
%A Oestges, Claude
%A Heaney, Sean F.
%A Scanlon, William G.
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Pedestrian-to-Vehicle Communications in an Urban Environment: Channel Measurements and Modeling
%X As wireless connectivity becomes increasingly ubiquitous, a greater emphasis will be placed upon the seamless integration of dissimilar networking technologies. One such example of this will occur in urban environments, where wearable devices and vehicular networks will operate in close proximity to one another. Clearly, a natural extension to both types of network is their interconnectivity through vehicle-to-pedestrian (V2P) or equivalently pedestrian-to-vehicle (P2V) communications as part of a much greater vehicle-to-X (V2X) based Intelligent Transportation System (ITS). To this end, we empirically investigate the P2V communications channel at 5.8 GHz for the case of a moving vehicle when a person positioned by the edge of a road was either stationary or walking parallel to the side of the highway. The measurements considered a chest mounted transmitter and four receiver locations on the vehicle covering the front wing mirrors and two positions on the roof, which simultaneously recorded the received signal power. To characterize the propagation mechanisms which are responsible for shaping the received signal in the P2V channel we decomposed it into its path loss, large-scale and small-scale fading components. We first show that although there was evidence of interference caused by multiple rays interacting with one another, the popular Two- Ray ground-reflection path loss model was unable to adequately describe the compounded effects of the vehicle and pedestrian’s body on the signal attenuation in the majority of the considered scenarios. Instead, we found that the overall path loss was well characterized using a dual-slope log-distance model, with lognormal large-scale fading. Due to the often severe small-scale fading that was observed in the P2V channel, we have been able to utilize the kappa-mu Extreme distribution with considerable success to characterize the worse than Rayleigh fading conditions which were encountered.
%K Electrical and Electronic Engineering
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%P 1-1
%D 2018
%@ 0018-926X (ISSN)
%@ 1558-2221 (e-ISSN)
%* peer-reviewed
%D 2018
%U Handle: http://hdl.handle.net/2078.1/208677
%R 10.1109/tap.2018.2885461
%0 Journal Article
%9 Article de recherche
%A Rottenberg, François
%A Mestre, Xavier
%A Horlin, François
%A Louveaux, Jérôme
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Performance Analysis of Linear Receivers for Uplink Massive MIMO FBMC-OQAM Systems
%K ICTM/ELEN
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%V 66
%N 3
%P 830-842
%D 2018
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2018
%U Handle: http://hdl.handle.net/2078.1/189423
%R 10.1109/TSP.2017.2778682
%0 Journal Article
%9 Article de recherche
%A Wang, Zijian
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Power Allocation for Energy Efficient Multiple Antenna Systems with Joint Total and Per-Antenna Power Constraints
%X An energy efficiency (EE) maximization problem with multiple transmit antennas (multiple-input-single-output or distributed antennas setups) is considered in this paper. Besides the constraint on the total transmit power, per-antenna transmit power constraints, and a total weighted power constraint are jointly considered. Moreover, a quality-of-service constraint is also considered. Both linear and nonlinear high power amplifier (HPA) cases are studied. Because the original problem for the linear HPA case is a fractional convex problem, Dinkelbach's algorithm is implemented to reformulate the problem. By investigating the Karush-Kuhn-Tucker conditions, the mathematical properties of the globally optimal solution are studied and proved, which provides a deeper understanding of the structure of power allocation among antennas. These properties also lead to a reduction of the complexity of the algorithms proposed to find the global optimum. For the nonlinear HPA cases, the reformulated problem after successive convex approximation is shown to be exactly in the same form as that of the previous problem with linear HPA with different weights of power consumption at each antenna. On the basis of numerical results comparing our EE maximization algorithms against different benchmarks, the efficiency and the superiority of our algorithms can be concluded.
%K power allocation
%K wireless
%K energy efficiency
%K ICTM:COMM
%K ICTM:SIGN
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%V 66
%N 10
%P 1-1
%D 2018
%@ 0090-6778 (ISSN)
%* peer-reviewed
%D 2018
%U Handle: http://hdl.handle.net/2078.1/209300
%R 10.1109/tcomm.2018.2839597
%0 Journal Article
%9 Article de recherche
%A Miao, Yang
%A Pedersen, Troels
%A Gan, Mingming
%A Vinogradov, Evgenii
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Reverberant Room-to-Room Radio Channel Prediction by Using Rays and Graphs
%X This paper proposes a hybrid modeling approach for prediction of the room-to-room radio propagation channel. The model combines ray tracing with propagation graph. The propagation graph vertices are obtained at each room by ray tracing with the assumption that the receive antenna (or transmit antenna) virtually locates on the surface of the separating wall between two rooms. Rays transmitted from one room to the other through the separating wall are deterministically calculated by Snell’s law of refraction. Predictions by the proposed model are compared with measurement data from an office-to-office scenario. The results show that the proposed modeling works with the simplest parameter settings, i.e. assuming no propagation from the room containing receive antenna to the room containing transmit antenna, ray tracing applied separately in each room only involves mechanism of line-of-sight and first order specular reflection.
%K Electrical and Electronic Engineering
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%P 1-1
%D 2018
%@ 0018-926X (ISSN)
%@ 1558-2221 (e-ISSN)
%* peer-reviewed
%D 2018
%U Handle: http://hdl.handle.net/2078.1/208678
%R 10.1109/tap.2018.2878088
%0 Journal Article
%9 Article de recherche
%A Torrea-Duran, Rodolfo
%A Morales Cespedes, Maximo
%A Plata-Chaves, Jorge
%A Vandendorpe, Luc
%A Moonen, Marc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Topology-Aware Space-Time Network Coding in Cellular Networks
%X Space-time network coding (STNC) is a time-division multiple access (TDMA)-based scheme that combines network coding and space-time coding by allowing relay nodes to combine the information received from different source nodes during the transmission phase and to forward the combined signal to a destination node in the relaying phase. However, STNC schemes require all the relay nodes to overhear the signals transmitted from all the source nodes in the network. They also require a large number of timeslots to achieve full diversity in a multipoint-to-multipoint transmission. Both conditions are particularly challenging for large cellular networks where, assuming a downlink transmission, base stations (BSs) and users only overhear a subset of all the BSs. In this paper, we exploit basic knowledge of the network topology in order to reduce the number of time-slots by allowing simultaneous transmissions from those BSs that do not overhear each other. Our results show that these topology-aware schemes are able to increase the spectral efficiency per time-slot and bit error rate with unequal transmit power and channel conditions.
%K ICTM:COMM
%K ICTM:SIGN
%G Anglais
%J IEEE Access
%B IEEE Access
%V 6
%N 1
%P 7565-7578
%D 2018
%@ 2169-3536 (e-ISSN)
%* peer-reviewed
%D 2018
%U Handle: http://hdl.handle.net/2078.1/209302
%R 10.1109/access.2017.2773709
%0 Journal Article
%9 Article de recherche
%A Rottenberg, François
%A Nguyen, T.-H.
%A Gorza, S.-P.
%A Horlin, François
%A Louveaux, Jérôme
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Advanced Chromatic Dispersion Compensation in Optical Fiber FBMC-OQAM Systems
%X We report on several methods for the chromatic dispersion (CD) compensation in optical fiber offset-QAM-based filterbank multicarrier (FBMC-OQAM) systems. We show that several equalization structures, initially proposed for wireless FBMC-OQAM systems, can also be applied to optical FBMC-OQAM systems to enhance the CD tolerance. The different CD compensation algorithms are numerically validated and compared to the conventional one tap equalizer in a 30 GBaud optical FBMC system, in terms of performance and complexity. Considering a 1-dB optical signal-to-noise ratio penalty at a bit-error-rate of 3.8×10(−3) and 256 subcarriers, the results show that the maximum CD tolerance of the frequency spreading method can be enhanced by a factor 10 and 30 for 4-OQAM and 16-OQAM modulations respectively compared to that of the conventional 1 tap equalizer, at the cost of higher complexity. Even though the other CD compensation methods provide a reduced CD tolerance compared to the frequency spreading method, they require less complexity and hence can be good alternatives.
%K Electrical and Electronic Engineering
%K and Optics
%K ICTEAM
%K ELEN
%G Anglais
%J IEEE Photonics Journal
%B IEEE Photonics Journal
%V 9
%N 6
%P 1-10
%D 2017
%@ 1943-0655 (e-ISSN)
%* peer-reviewed
%D 2017
%U Handle: http://hdl.handle.net/2078.1/189928
%R 10.1109/jphot.2017.2773667
%0 Journal Article
%9 Article de recherche
%A Doone, Michael G.
%A Cotton, Simon L.
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T An Experimental Investigation into the Impact of Vehicular Traffic on Interpersonal Wearable-to-Wearable Communications Channels
%X In this paper, we have investigated the effects of vehicular traffic on interpersonal wearable-to-wearable (W2W) communications channels in an urban environment at 2.45 GHz. In particular, we have studied the perturbations in the received signal caused by different types of vehicles as they passed through a channel between two persons who maintained various relative orientations while positioned at the opposite sides of a road. As the channel underwent different fading mechanisms depending on whether the vehicle was approaching, transitioning (i.e., intersecting the direct signal path), or receding from the persons, the overall disturbance was appropriately segmented depending on the journey stage. The results have shown that relative body orientation was a significant factor when considering the impact that a vehicle can have on a W2W link. When both persons faced the oncoming traffic, the link was particularly susceptible to significant fading events with variations in the received signal power from the unperturbed state as great as 44.1 dB observed to occur. For all of the journey stages, irrespective of the relative orientation of the persons, the logarithmically transformed long-term fading process was found to be multimodal and well described by a Gaussian mixture model. During the transitioning phase, shadowing caused by the passing automobile obstructing the line-of-sight signal path was found to be the main contributor to the signal fading. However, probably the most remarkable result of the channel characterization work conducted in this paper was the severity of the short-term fading often observed. Such was the intensity of the measured envelope fluctuation in many of the scenarios, we have been able to utilize the recently proposed κ−μ extreme distribution with great success and in the process, provide a further important empirical validation of this new fading model. Moreover, we have used the resistor-average distance, which is derived from the Kullback–Leibler distance to show the improved fit that the κ−μ extreme distribution offers compared with the κ−μ distribution when used to model the W2W channel in this fading environment.
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%V 65
%N 10
%P 5418 - 5430
%D 2017
%@ 0018-926X (ISSN)
%@ 1558-2221 (e-ISSN)
%* peer-reviewed
%D 2017
%U Handle: http://hdl.handle.net/2078.1/187998
%R 10.1109/TAP.2017.2738071
%0 Journal Article
%9 Article de recherche
%A Wang, Zijian
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Antenna Selection for Energy Efficient MISO Systems
%X This letter studies the mathematical property of the energy-efficiency (EE) function for multiple-input single-output systems with transmit antenna selection. We prove that the monotonicity of the function is guaranteed if the system signal-to-noise ratio satisfies a sufficient condition, which is quite feasible in practice. Based on this property, an algorithm with low complexity is proposed to find the maximum EE. The monotonicity of the function and the advantage of the proposed algorithm are confirmed by numerical results.
%K Modelling and Simulation
%K Electrical and Electronic Engineering
%K Computer Science Applications
%K ICTM:COMM
%K ICTM:SIGN
%G Anglais
%J IEEE Communications Letters
%B IEEE Communications Letters
%V 21
%P 2758-2761
%D 2017
%@ 1089-7798 (ISSN)
%* peer-reviewed
%D 2017
%U Handle: http://hdl.handle.net/2078.1/191164
%R 10.1109/lcomm.2017.2753782
%0 Journal Article
%9 Éditorial
%A Ai, Bo
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Antennas and Propagation for Future Transportation Systems
%X Future transportation systems (FTS) are advanced applications that aim to provide innovative services relating to different modes of transport and to enable various users to become safer and better informed. Compared to intelligent transportation systems, which are mainly defined in the field of road transport, FTS refers to all modes of transport, such as railway, road, air,water, and space, and the field is divided into infrastructure, vehicles, and operations. Recent advances in FTS have led to requirements for improvements and enhancements to systems used for communications. As with any communication system, the performance is ultimately determined by the antenna system and propagation channel, and the design, testing, and improvement of the system hinges critically on our understanding of the antenna theory and propagation characteristics.
%K ICTEAM:COMM
%G Anglais
%J IEEE Antennas and Wireless Propagation Letters
%B IEEE Antennas and Wireless Propagation Letters
%V 16
%N 2017
%P 1413 - 1414
%D 2017
%@ 1536-1225 (ISSN)
%@ 1548-5757 (e-ISSN)
%* peer-reviewed
%D 2017
%U Handle: http://hdl.handle.net/2078.1/188003
%R 10.1109/LAWP.2017.2699259
%0 Journal Article
%9 Article de recherche
%A Pan, Yun-Tian
%A Zheng, Guo-Xin
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Characterization of Polarized Radio Channel with Leaky Coaxial Cable in a Tunnel-like Environment
%X This letter presents the measurements carried out in a tunnel-like scenario at 1.8 GHz using a leaky coaxial cable as the transmitting antenna. The cable polarization has been considered and the channel properties under different polarized combinations have been investigated. The results reveal that the decay rate of received power is polarized-dependent and smaller than the case of dipole transmitting. The cross-polarization discrimination is distance-dependent. Large-scale fading obeys the generalized extreme value distribution. Analysis on K-factor shows that it behaves randomly with the change of distance and can be fitted by a Normal distribution. Rice distribution fits better to small-scale fading with a large K-factor, while Weibull distribution is more suitable with a small K-factor.
%K ICTEAM:COMM
%G Anglais
%J IEEE Antennas and Wireless Propagation Letters
%B IEEE Antennas and Wireless Propagation Letters
%V 2017
%N 16
%P 2803-2807
%D 2017
%@ 1536-1225 (ISSN)
%@ 1548-5757 (e-ISSN)
%* peer-reviewed
%D 2017
%U Handle: http://hdl.handle.net/2078.1/188242
%R 10.1109/LAWP.2017.2747773
%0 Journal Article
%9 Article de recherche
%A Van Hecke, Jeroen
%A Del Fiorentino, Paolo
%A Lottici, Vincenzo
%A Giannetti, Filippo
%A Vandendorpe, Luc
%A Moeneclaey, Marc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Distributed Dynamic Resource Allocation for Cooperative Cognitive Radio Networks With Multi-Antenna Relay Selection
%X A cognitive radio scenario is considered where the signals transmitted by a secondary user (SU) are relayed by multi-antenna relays using an amplify-and-forward cooperation protocol. In this paper, the optimal power allocation and beamforming scheme is derived for the SU transmitters (SU-TXs), which minimizes the exact outage probability of the SU network with relay selection, under both a transmit power constraint and a constraint on the interference power generated at every primary user receiver. After deriving the optimal structure of the beamforming matrix, several distributed resource allocation algorithms are obtained for different levels of channel state information (CSI) at the SU-TXs: perfect CSI and imperfect CSI are considered, along with the case where only channel distribution information is available. The numerical results show that the multi-antenna relays can significantly improve the performance of the SU network, which would otherwise be severely limited by the harsh interference constraints. Furthermore, we also investigate how the number of relays, the number of antennas, and the level of CSI impact the performance of the SU network. Finally, we point out that the proposed algorithms outperform several algorithms presented in the literature.
%K Electrical and Electronic Engineering
%K Applied Mathematics
%K Computer Science Applications
%K ICTM:COMM
%K ICTM:SIGN
%G Anglais
%J IEEE Transactions on Wireless Communications
%B IEEE Transactions on Wireless Communications
%V 16
%P 1236-1249
%D 2017
%@ 1536-1276 (ISSN)
%* peer-reviewed
%D 2017
%U Handle: http://hdl.handle.net/2078.1/189869
%R 10.1109/twc.2016.2642942
%0 Journal Article
%9 Article de recherche
%A Nguyen, Trung-Hien
%A Rottenberg, François
%A Horlin, François
%A Louveaux, Jérôme
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Efficient Chromatic Dispersion Compensation and Carrier Phase Tracking for Optical Fiber FBMC/OQAM Systems
%X Offset-QAM-based filterbank multicarrier (FBMC/OQAM) is an attractive candidate to improve the spectral containment of optical fiber communication systems, especially when considering a sufficiently high number of subcarriers. As for other multicarrier modulations, the chromatic dispersion (CD) compensation is simplified in FBMC/OQAM systems since it is performed in the frequency domain. Unfortunately, FBMC/OQAM systems are sensitive to the laser phase noise (PN). The PN becomes difficult to mitigate when the number of subcarriers increases due to the increased symbol period. It results in inter-carrier interference (ICI) and inter-symbol interference (ISI) due to the loss of OQAM orthogonality. In this paper, we consider the use of moderate numbers of subcarriers to allow for simpler PN tracking. Consequently, more advanced CD compensation methods are required and a trade-off between CD and PN compensations needs to be studied. In this paper, the frequency sampling equalizer is used for the CD compensation, whereas an innovative adaptive maximum likelihood estimator is used for the PN compensation. A methodology is then presented to analyze this performance trade-off between CD and PN compensations, and design the desirable system parameters such as the number of subcarriers and the equalizer length. This is illustrated in the case of a terrestrial long-haul FBMC/OQAM transmission system, with 400-kHz laser linewidth and a 1000 km optical link.
%G Anglais
%J IEEE/OSA Journal of Lightwave Technology
%B IEEE/OSA Journal of Lightwave Technology
%V 35
%N 14
%P 2909 - 2916
%D 23 May 2017
%@ 0733-8724 (ISSN)
%@ 1558-2213 (e-ISSN)
%* peer-reviewed
%D 2017
%U Handle: http://hdl.handle.net/2078.1/187819
%R 10.1109/JLT.2017.2707179
%0 Journal Article
%9 Article de recherche
%A Torrea-Duran, Rodolfo
%A Rosas, Fernando
%A Pollin, Sofie
%A Vandendorpe, Luc
%A Moonen, Marc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Exploiting the overhearing capabilities of transmitting nodes to increase the energy efficiency in dense networks
%X The 1000-fold capacity increase envisioned by dense 5G networks results also in a tremendous increase in the energy consumption of the whole network. Utilizing relays in combination with physical-layer network coding (PNC) has been proposed as an energy-efficient solution to this problem by creating several short-distance low-power transmissions and by reducing the transmission time. However, deploying relay nodes can be very costly for dense networks. On the other hand, the proximity of transmitting nodes in dense networks allows the transmitting nodes to serve as relays and retransmit the signals overheard from other transmitting nodes using PNC. This approach has been shown to increase the spectral efficiency, but the impact on energy efficiency has not been studied yet. Therefore, in this paper, we analyze two approaches that exploit the overhearing capabilities of the transmitting nodes in terms of spectral efficiency, energy efficiency, and success rate. We then provide a low-complexity power control strategy that achieves a performance close to the optimal for each approach. We show that when at least one indirect link is stronger than the direct links, exploiting the overhearing capabilities of the transmitting nodes provides the highest performance in both the transmit power-dominated and circuit power-dominated regimes.
%K Signal Processing
%K Computer Networks and Communications
%K Computer Science Applications
%K ICTM:COMM
%K ICTM:SIGN
%G Anglais
%J EURASIP Journal on Wireless Communications and Networking
%B EURASIP Journal on Wireless Communications and Networking
%V 2017
%P 1-16
%D 2017
%@ 1687-1499 (e-ISSN)
%* peer-reviewed
%D 2017
%U Handle: http://hdl.handle.net/2078.1/189871
%R 10.1186/s13638-017-0970-8
%0 Journal Article
%9 Article de recherche
%A Castel, Thijs
%A Lemey, Sam
%A Van Torre, Patrick
%A Oestges, Claude
%A Rogier, Hendrik
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Four-element Ultra-Wideband Textile Cross Array for Dual Spatial and Dual Polarization Diversity
%X The emergence of miniaturized flexible electronics enables on-duty first responders to collect biometrical and environmental data through multiple on-body sensors, integrated into their clothing. However, gathering these life-saving data would be useless if they cannot set up reliable, preferable high data rate, wireless communication links between the sensors and a remote base station. Therefore, we have developed a fourelement ultra-wideband textile cross array, that combines dualspatial and dual-polarization diversity, and is easily deployable in a first responder’s garment. The impedance bandwidth of the array equals 1.43 GHz, while mutual coupling between its elements remains below -25 dB. For a maximal bit error rate of 1e-4, the array realizes a diversity gain of 24.81dB. When applying Adaptive Subcarrier modulation, the mean throughput per OFDM subcarrier increases by an extra bit/symbol when comparing fourth to second order diversity.
%K ICTEAM:COMM
%G Anglais
%J IEEE Antennas and Wireless Propagation Letters
%B IEEE Antennas and Wireless Propagation Letters
%V 16
%N 6
%P 481 - 484
%D 2017
%@ 1536-1225 (ISSN)
%@ 1548-5757 (e-ISSN)
%* peer-reviewed
%D 2017
%U Handle: http://hdl.handle.net/2078.1/177104
%R 10.1109/LAWP.2016.2585308
%0 Journal Article
%9 Article de recherche
%A Feuillen, Thomas
%A Pairon, Thomas
%A Craeye, Christophe
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Localization of Rotating Targets Using a Monochromatic Continuous-Wave Radar
%X A simple and efficient localization method for rotating objects is introduced. The estimation of the position is performed using only a continuous-wave radar with multiple receiving antennas. The method relies on the establishment of a linear relation between the interelement phase shifts and frequency, which is exploitable in the near-to-intermediate field. The method is introduced, and its independence with respect to the shape of the target demonstrated. Monte Carlo simulations are performed to study the variance of the proposed estimator. An experimental validation is carried out with a rotating cylinder and shows good agreement with simulations.
%K Radar
%K Estimation
%K Radar antennas
%K Receiving antennas
%K Frequency modulation
%K Signal to noise ratio
%K Angular velocity
%K WAVE
%G Anglais
%J IEEE Antennas and Wireless Propagation Letters
%B IEEE Antennas and Wireless Propagation Letters
%V 16
%P 2598 - 2601
%D 2017
%@ 1536-1225 (ISSN)
%@ 1548-5757 (e-ISSN)
%* peer-reviewed
%D 2017
%U Handle: http://hdl.handle.net/2078.1/189817
%R 10.1109/LAWP.2017.2735020
%0 Journal Article
%9 Article de recherche
%A Bogale, Tadilo Endeshaw
%A Le, Long Bao
%A Wang, Xianbin
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Multipath Multiplexing for Capacity Enhancement in SIMO Wireless Systems
%X This paper proposes a novel and simple orthogonal faster than Nyquist (OFTN) data transmission and detection approach for a single input multiple output system. It is assumed that the signal having a bandwidth B is transmitted through a wireless channel with L multipath components. Under this assumption, this paper provides a novel and simple OFTN transmission and symbol-by-symbol detection approach that exploits the multiplexing gain obtained by the multipath characteristic of wideband wireless channels. It is shown that the proposed design can achieve a higher transmission rate than the existing one [i.e., orthogonal frequency division multiplexing (OFDM)]. Furthermore, the achievable rate gap between the proposed approach and that of the OFDM increases as the number of receiver antennas increases for a fixed value of L. This implies that the performance gain of the proposed approach can be very significant for a large-scale multi-antenna wireless system. The superiority of the proposed approach is shown theoretically and confirmed via numerical simulations. Specifically, we have found upper-bound average rates of 15 and 28 bps/Hz with the OFDM and proposed approaches, respectively, in a Rayleigh fading channel with 32 receive antennas and signal-to-noise ratio of 15.3 dB. The extension of the proposed approach for different system setups and associated research problems is also discussed.
%K Electrical and Electronic Engineering
%K Applied Mathematics
%K Computer Science Applications
%K ICTM:COMM
%K ICTM:SIGN
%G Anglais
%J IEEE Transactions on Wireless Communications
%B IEEE Transactions on Wireless Communications
%V 16
%P 6895-6911
%D 2017
%@ 1536-1276 (ISSN)
%* peer-reviewed
%D 2017
%U Handle: http://hdl.handle.net/2078.1/189863
%R 10.1109/twc.2017.2732980
%0 Journal Article
%9 Article de recherche
%A Makhoul, Gloria
%A Mani, Francesco
%A DErrico, Raffaele
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T On the Modeling of Time Correlation Functions for Mobile-to-Mobile Fading Channels in Indoor Environments
%X This letter studies time correlation functions of mobile-to-mobile (M2M) fading channels, based on a measurement campaign carried out in an indoor environment at 2.48 GHz. The time correlation properties are characterized for different mobility patterns. In order to depict the time correlation properties, a general model for the time correlation function is given assuming a typical M2M propagation scenario, where some local scatterers are moving with random velocities and in random directions. Subsequently, for each measured type of mobility pattern, an analytical autocorrelation function is derived and successfully compared to the measurement data.
%K ICTEAM:COMM
%G Anglais
%J IEEE Antennas and Wireless Propagation Letters
%B IEEE Antennas and Wireless Propagation Letters
%V 16
%N 3
%P 549-552
%D 2017
%@ 1536-1225 (ISSN)
%@ 1548-5757 (e-ISSN)
%* peer-reviewed
%D 2017
%U Handle: http://hdl.handle.net/2078.1/187999
%R 10.1109/LAWP.2017.2682959
%0 Journal Article
%9 Article de recherche
%A Determe, Jean-Francois
%A Louveaux, Jérôme
%A Jacques, Laurent
%A Horlin, Francois
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T On the Noise Robustness of Simultaneous Orthogonal Matching Pursuit
%X In this paper, the joint support recovery of several sparse signals whose supports present similarities is examined. Each sparse signal is acquired using the same noisy linear measurement process, which returns fewer observations than the dimension of the sparse signals. The measurement noise is assumed additive, Gaussian, and admits different variances for each sparse signal that is measured. Using the theory of compressed sensing, the performance of simultaneous orthogonal matching pursuit (SOMP) is analysed for the envisioned signal model. The cornerstone of this paper is a novel analysis method upper bounding the probability that SOMP recovers at least one incorrect entry of the joint support during a prescribed number of iterations. Furthermore, the probability of SOMP failing is investigated whenever the number of sparse signals being recovered simultaneously increases and tends to infinity. In particular, convincing observations and theoretical results suggest that SOMP committing no mistake in the noiseless case does not guarantee the absence of error in the noisy case whenever the number of acquired sparse signals scales to infinity. Finally, simulation results confirm the validity of the theoretical results.
%K AERC
%K Simultaneous orthogonal matching pursuit
%K compressed sensing
%K restricted isometry property
%K asymptotic recovery
%K Gaussian
%K noise
%K MMV
%K ICTM/ELEN
%K ISPGroup
%K ICTEAM:SIGN
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%V 65
%N 4
%P 864-875
%D 2017
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2017
%U Handle: http://hdl.handle.net/2078.1/182869
%R 10.1109/TSP.2016.2626244
%0 Journal Article
%9 Article de recherche
%A Mani, Francesco
%A Makhoul, Gloria
%A Oestges, Claude
%A D Errico, Raffaele
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T On the generation of correlated short and long term fading for multiple BANs
%X This work presents a time-varying multi-BAN channel model implementation including both on-body and Bodyto- Body links. Channel time correlation properties are modeled with an auto-regressive method with the exception of Body-to- Body short term fading. This last component shows an important dependence on the body positions and specifically on the mutual orientation of the bodies. For this reason it requested a dedicated implementation with a Cholesky decomposition based method. Simulated results of the implementation are validated with measurements and a good agreement between the two is found.
%K ICTEAM:COMM
%G Anglais
%J IEEE Antennas and Wireless Propagation Letters
%B IEEE Antennas and Wireless Propagation Letters
%V 16
%N 7
%P 1867 - 1870
%D 2017
%@ 1536-1225 (ISSN)
%@ 1548-5757 (e-ISSN)
%* peer-reviewed
%D 2017
%U Handle: http://hdl.handle.net/2078.1/177102
%R 10.1109/LAWP.2016.2590474
%0 Journal Article
%9 Article de recherche
%A Rottenberg, François
%A Mestre, Xavier
%A Petrov, Dmitry
%A Horlin, François
%A Louveaux, Jérôme
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Parallel Equalization Structure for MIMO FBMC-OQAM Systems Under Strong Time and Frequency Selectivity
%X Offset-QAM-based filterbank multicarrier (FBMC-OQAM) has been shown to be a promising alternative to cyclic prefix-orthogonal frequency division multiplexing (CP-OFDM) for the future generation of wireless communication systems. Unfortunately, as the channel gets more selective in time and frequency, the FBMC-OQAM orthogonality is progressively destroyed and distortion appears after the demodulation process at the receiver. While channel frequency selectivity has been very widely studied in the FBMC literature, the impact of time selectivity of the channel has not received that much attention. In this paper, the effect of the two types of selectivity on a multiple-input multiple-output (MIMO) FBMC system is characterized and a parallel equalization structure that can compensate for the doubly dispersive nature of the channel is proposed. This design uses multiple analysis filterbanks (AFB) and extends previous approaches that were dealing only with channel frequency selectivity. A theoretical approximation of the remaining distortion after equalization is given. The study is performed for a general MIMO system but can also be particularized to single-input single-output (SISO) systems. Simulation results demonstrate the high efficiency of the proposed receiver structure and the accuracy of the theoretical approximations is verified.
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%V 65
%N 17
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2017
%U Handle: http://hdl.handle.net/2078.1/185225
%R 10.1109/TSP.2017.2711534
%0 Journal Article
%9 Article de recherche
%A Vinogradov, Evgenii
%A Bamba, Aliou
%A Joseph, Wout
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Physical-Statistical Modeling of Dynamic Indoor Power Delay Profiles
%X This paper presents a physical-statistical radio channel power delay profiles model for room-to-room communication systems combining the room electromagnetic theory for modeling deterministic channel components with a geometry-based stochastic channel model with time-variant statistics for modeling stochastic components. The deterministic channel component, i.e., mean power delay spectrum, is comprised of specularly reflected paths plus diffuse components due to scattering and diffraction. The specular components are modeled with a set Dirac function, whereas the diffuse components modeling approach is a room electromagnetic theory-based model. Dynamic indoor communication channels are characterized by a non-stationary time- and delay-fading process due to changes in the environment. We analyze and model the time-delay variability of channels using K-factor for small-scale variations and the t -location scale distribution parameters for large-scale variations. It turns out that these parameters cannot be assumed to be constant in time and delay. After modeling of time-delay variations of the first order statistics, we generate channel realizations with appropriate second order statistics. As the result, the presented model enables to describe the evolution of the power delay profile in the time domain.
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Wireless Communications
%B IEEE Transactions on Wireless Communications
%V 16
%N 10
%P 6493-6502
%D 2017
%@ 1536-1276 (ISSN)
%@ 1558-2248 (e-ISSN)
%* peer-reviewed
%D 2017
%U Handle: http://hdl.handle.net/2078.1/188128
%R 10.1109/TWC.2017.2724034
%0 Journal Article
%9 Article de recherche
%A Rottenberg, François
%A Mestre, Xavier
%A Horlin, François
%A Louveaux, Jérôme
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Single-Tap Precoders and Decoders for Multi-User MIMO FBMC-OQAM under Strong Channel Frequency Selectivity
%X The design of linear precoders or decoders for multiuser multiple-input multiple-output filterbank multicarrier (FBMC) modulations in the case of a strong channel frequency selectivity is presented. The users and the base station (BS) communicate using space division multiple access. The low complexity proposed solution is based on a single tap per-subcarrier precoding/decoding matrix at the BS in the downlink/uplink. As opposed to classical approaches that assume flat channel frequency selectivity at the subcarrier level, the BS does not make this assumption and takes into account the distortion caused by channel frequency selectivity. The expression of the FBMC asymptotic mean squared error (MSE) in the case of strong channel selectivity derived in earlier works is developed and extended. The linear precoders and decoders are found by optimizing the MSE formula under two design criteria, namely zero forcing or minimum MSE. Finally, simulation results demonstrate the performance of the optimized design. As long as the number of BS antennas is larger than the number of users, it is shown that those extra degrees of freedom can be used to compensate for the channel frequency selectivity.
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%V 65
%N 3
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2017
%U Handle: http://hdl.handle.net/2078.1/179888
%R 10.1109/TSP.2016.2621722
%0 Journal Article
%9 Article de recherche
%A Wang, Zijian
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Subcarrier Allocation and Precoder Design for Energy Efficient MIMO-OFDMA Downlink Systems
%X This paper studies the subcarrier allocation and precoder design problem for downlink multiple-input-multipleoutput (MIMO)- orthogonal frequency-division multiple access (OFDMA) systems. The criterion is to maximize the energy efficiency (EE) of the system. We adopt the time-sharing concept to allocate each subcarrier to one user, which results in a criterion similar with that of rate maximization. However, this approach does not make it possible to solve the problem for any value of the transmit power. We found that there exist gaps along the direction of total transmit power when the user selection switches for each subcarrier, which leads to a discontinuous EE function, for which quasi-concavity has to be checked. We first show that the sufficient conditions obtained for the subcarrier allocation approach are the optimal ones among all possibilities with the same transmit power. Then we show that the proposed subcarrier allocation results in a discontinuous and quasi-concave EE function. We also give an upper bound of the EE function when the proposed sufficient conditions are not met. Finally, we propose an algorithm to find the maximal EE and its performance is illustrated by means of numerical results.
%K ICTEAM
%K ICTEAM:COMM
%K ICTEAM:SIGN
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%V 65
%N 1
%P 136-146
%D 2017
%@ 0090-6778 (ISSN)
%@ 1558-0857 (e-ISSN)
%* peer-reviewed
%D 2017
%U Handle: http://hdl.handle.net/2078.1/178652
%R 10.1109/TCOMM.2016.2626370
%0 Journal Article
%9 Article de recherche
%A Van Hecke, J.
%A Del Fiorentino, P.
%A Andreotti, R.
%A Lottici, V.
%A Giannetti, F.
%A Vandendorpe, Luc
%A Moeneclaey, M.
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Adaptive coding and modulation using imperfect CSI in cognitive BIC-OFDM systems
%X This work investigates adaptive coding and modulation (ACM) algorithms under the realistic assumption that the available channel state information (CSI) at the transmitter is imperfect due to estimation errors and/or feedback delays. First, we introduce an optimal performance metric for the secondary user (SU) bit-interleaved coded orthogonal frequency division multiplexing (BIC-OFDM) system, called the expected goodput (EGP). By using an accurate modeling approximation, we succeed in deriving a tractable and very accurate approximation for the EGP. This approximate EGP (AEGP) is then used for the derivation of several ACM algorithms which optimize the code rate and bit and energy allocation under a constraint on the interference caused to the PU network. In the numerical results, we show that the AEGP is far more accurate than previous attempts to model the GP in the presence of imperfect CSI. Further, we verify that, in spite of the imperfect nature of the available CSI, the derived ACM algorithms significantly increase the goodput of the SU network, compared to a non-adaptive selection of the transmission parameters. © 2016, The Author(s).
%K Adaptive coding and modulation (ACM)
%K Effective SNR mapping (ESM)
%K Goodput
%K Imperfect channel state information
%K Orthogonal frequency division multiplexing (OFDM)
%K ICTEAM:COMM
%K ICTEAM:SIGN
%G Anglais
%J Eurasip Journal on Wireless Communications and Networking
%B Eurasip Journal on Wireless Communications and Networking
%V 2016
%N 1
%P 1-14
%D 2016
%@ 1687-1472 (ISSN)
%@ 1687-1499 (e-ISSN)
%* peer-reviewed
%D 2016
%U Handle: http://hdl.handle.net/2078.1/178651
%0 Journal Article
%9 Article de recherche
%A Van Hecke, Jeroen
%A Del Fiorentino, Paolo
%A Andreotti, Riccardo
%A Lottici, Vincenzo
%A Giannetti, Filippo
%A Vandendorpe, Luc
%A Moeneclaey, Marc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Adaptive coding and modulation using imperfect CSI in cognitive BIC-OFDM systems
%X This work investigates adaptive coding and modulation (ACM) algorithms under the realistic assumption that the available channel state information (CSI) at the transmitter is imperfect due to estimation errors and/or feedback delays. First, we introduce an optimal performance metric for the secondary user (SU) bit-interleaved coded orthogonal frequency division multiplexing (BIC-OFDM) system, called the expected goodput (EGP). By using an accurate modeling approximation, we succeed in deriving a tractable and very accurate approximation for the EGP. This approximate EGP (AEGP) is then used for the derivation of several ACM algorithms which optimize the code rate and bit and energy allocation under a constraint on the interference caused to the PU network. In the numerical results, we show that the AEGP is far more accurate than previous attempts to model the GP in the presence of imperfect CSI. Further, we verify that, in spite of the imperfect nature of the available CSI, the derived ACM algorithms significantly increase the goodput of the SU network, compared to a non-adaptive selection of the transmission parameters.
%K ICTEAM
%K ICTEAM/SIGN
%K ICTEAM/COMM
%G Anglais
%J Eurasip Journal on Wireless Communications and Networking
%B Eurasip Journal on Wireless Communications and Networking
%V 2016
%N 1
%P 1-14
%D 2016
%@ 1687-1472 (ISSN)
%@ 1687-1499 (e-ISSN)
%* peer-reviewed
%D 2016
%U Handle: http://hdl.handle.net/2078.1/181375
%R 10.1186/s13638-016-0739-5
%0 Journal Article
%9 Article de recherche
%A Castel, Thijs
%A Van Torre, Patrick
%A Vallozzi, Luigi
%A Marinova, Marina
%A Lemey, Sam
%A Joseph, Wout
%A Oestges, Claude
%A Rogier, Hendrik
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Capacity of Broadband Body-to-Body Channels Between Firefighters Wearing Textile SIW Antennas
%X Reliable, high-data rate indoor communication is essential to transfer crucial information between firefighters for improving their safety and decreasing the number of casualties caused by indoor fires. Since electronic monitoring systems, including antennas implemented inside the firefighter jacket, should provide high data rates, communication over a wideband channel is required. We study an 80-MHz-wide body-to-body channel at 3.6 GHz between two firefighters of a Rapid Intervention Team (RIT) performing the primary search for victims, by static and dynamic channel sounder measurements. Two ultra-wideband (UWB) substrate integrated waveguide (SIW) cavity-backed slot textile antennas were unobtrusively deployed in the front and the back sections of the firefighters' jackets, providing up to 2×2 MIMO communication. We calculate the achievable single-input single-output (SISO)-, single-input multiple-output (SIMO)-, multiple-input single-output (MISO)-, and multiple-input multiple-output (MIMO)-orthogonal frequency division multiplexing (OFDM) capacities for realistic indoor broadband body-to-body communication channels between two firefighters. Furthermore, we analyze implementations of one-dimensional (1-D) spatial waterfilling and two-dimensional (2-D) space-frequency waterfilling, studying their ability to further enhance transmission of live sensor data, pictures or videos between mobile firefighters.
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%V 64
%N 5
%P 1918-1931
%D 2016
%@ 0018-926X (ISSN)
%@ 1558-2221 (e-ISSN)
%* peer-reviewed
%D 2016
%U Handle: http://hdl.handle.net/2078.1/177103
%R 10.1109/TAP.2016.2535488
%0 Journal Article
%9 Synthèse de littérature
%A He, Ruisi
%A Ai, Bo
%A Wang, Gongpu
%A Guan, Ke
%A Zhong, Zhangdui
%A Molisch, Andreas F.
%A Briso-Rodriguez, Cesar
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T High-Speed Railway Communications: From GSM-R to LTE-R
%X High-speed railways (HSRs) improve the quality of rail services, yield greater customer satisfaction, and help to create socioeconomically balanced societies [1]. This highly efficient transport mode creates significant challenges in terms of investment, technology, industry, and environment. To handle increasing traffic, ensure passenger safety, and provide real-time multimedia information, a new communication system for HSR is required. In the last decade, public networks have been evolving from voice-centric second-generation systems, e.g., Global System for Mobile Communications (GSM) with limited capabilities, to fourth-generation (4G) broad-band systems that offer higher data rates, e.g., long-term evolution (LTE). It is thus relevant for HSR to replace the current GSM-railway (GSM-R) technology with the next-generation railway-dedicated communication system providing improved capacity and capability.
%K ICTEAM:COMM
%G Anglais
%J IEEE Vehicular Technology Magazine : connecting the mobile world
%B IEEE Vehicular Technology Magazine : connecting the mobile world
%V 11
%N 3
%P 49-58
%D 2016
%@ 1556-6072 (ISSN)
%@ 1556-6080 (e-ISSN)
%* peer-reviewed
%D 2016
%U Handle: http://hdl.handle.net/2078.1/177100
%R 10.1109/MVT.2016.2564446
%0 Journal Article
%9 Article de recherche
%A Determe, Jean-Francois
%A Louveaux, Jérôme
%A Jacques, Laurent
%A Horlin, Francois
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Improving the Correlation Lower Bound for Simultaneous Orthogonal Matching Pursuit
%X The simultaneous orthogonal matching pursuit (SOMP) algorithm aims to find the joint support of a set of sparse signals acquired under a multiple measurement vector model. Critically, the analysis of SOMP depends on the maximal inner product of any atom of a suitable dictionary and the current signal residual, which is formed by the subtraction of previously selected atoms. This inner product, or correlation, is a key metric to determine the best atom to pick at each iteration. This letter provides, for each iteration of SOMP, a novel lower bound of the aforementioned metric for the atoms belonging to the correct and common joint support of the multiple signals. Although the bound is obtained for the noiseless case, its main purpose is to intervene in noisy analyses of SOMP. Finally, it is shown for specific signal patterns that the proposed bound outperforms state-of-the-art results for SOMP and orthogonal matching pursuit (OMP) as a special case.
%K noisy analysis
%K correlation lower bound improvement
%K simultaneous orthogonal matching pursuit algorithm
%K SOMP algorithm
%K sparse signal acquisition
%K multiple measurement vector model
%K suitable dictionary
%K current signal residual
%K ISPGroup
%K ICTM/ELEN
%K ICTEAM:SIGN
%G Anglais
%J IEEE Signal Processing Letters
%B IEEE Signal Processing Letters
%V 23
%N 11
%P 1642-1646
%D 2016
%@ 1070-9908 (ISSN)
%@ 1558-2361 (e-ISSN)
%* peer-reviewed
%D 2016
%U Handle: http://hdl.handle.net/2078.1/178294
%R 10.1109/LSP.2016.2612759
%0 Journal Article
%9 Article de recherche
%A Hanssens, Brecht
%A Tanghe, Emmeric
%A Martens, Luc
%A Oestges, Claude
%A Joseph, Wout
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Measurement-Based Analysis of Delay-Doppler Characteristics in an Indoor Environment
%X An analysis of delay-Doppler characteristics in the presence of moving people is presented for short-range communication in an indoor environment. Channel-sounding measurements have been carried out at 3.6 GHz in a crowded university hall during several short and long breaks in-between courses. During three consecutive days, the measurements were repeated with different positions for the transmit and receive antennas. In this study, the behavior of the maximum Doppler shift and the Doppler spread was analyzed in the time-delay domain as a function of the occupation of the hall, the polarizations of the 2 × 2 MIMO antennas, and their positions in the hall. The measurements reveal a clear distinction between the Doppler spread of the short and long breaks in the campaign, indicating a distinctive power distribution of their Doppler spectra. In addition, there is a significant contrast between the Doppler characteristics of the co- and cross-polarizations. Measurements at several positions reveal the importance of characterizing multipaths and show that the Doppler effect depends on the position of the antennas in the environment. In addition, this work also shows that the Doppler spectrum can be accurately modeled by a Cauchy distribution, allowing for the generation of parameters to describe Doppler characteristics.
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%V 64
%N 1
%P 370-374
%D 2016
%@ 0018-926X (ISSN)
%@ 1558-2221 (e-ISSN)
%* peer-reviewed
%D 2016
%U Handle: http://hdl.handle.net/2078.1/177105
%R 10.1109/TAP.2015.2503480
%0 Journal Article
%9 Article de recherche
%A Determe, Jean-François
%A Louveaux, Jérôme
%A Jacques, Laurent
%A Horlin, François
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T On The Exact Recovery Condition of Simultaneous Orthogonal Matching Pursuit
%X Several exact recovery criteria (ERC) ensuring that orthogonal matching pursuit (OMP) identifies the correct support of sparse signals have been developed in the last few years. These ERC rely on the restricted isometry property (RIP), the associated restricted isometry constant (RIC) and sometimes the restricted orthogonality constant (ROC). In this paper, three of the most recent ERC for OMP are examined. The contribution is to show that these ERC remain valid for a generalization of OMP, entitled simultaneous orthogonal matching pursuit (SOMP), that is capable to process several measurement vectors simultaneously and return a common support estimate for the underlying sparse vectors. The sharpness of the bounds is also briefly discussed in light of previous works focusing on OMP.
%K Compressed sensing
%K exact recovery condition
%K restricted isometry constant
%K restricted isometry property
%K restricted orthogonality constant
%K simultaneous orthogonal matching pursuit
%K ICTEAM/ELEN
%K ISPGroup
%K ICTEAM:SIGN
%G Anglais
%J IEEE Signal Processing Letters
%B IEEE Signal Processing Letters
%V 23
%N 1
%P 164-168
%D 2016
%@ 1070-9908 (ISSN)
%@ 1558-2361 (e-ISSN)
%* peer-reviewed
%D 2016
%U Handle: http://hdl.handle.net/2078.1/168615
%R 10.1109/LSP.2015.2506989
%0 Journal Article
%9 Article de recherche
%A Bogale, T.E.
%A Le, L.B.
%A Haghighat, A.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T On the Number of RF Chains and Phase Shifters, and Scheduling Design With Hybrid Analog-Digital Beamforming
%X This paper considers hybrid beamforming (HB) for 7 downlink multiuser massive multiple-input multiple-output 8 (MIMO) systems with frequency selective channels. The proposed 9 HB design employs sets of digitally controlled phase (ﬁxed phase) paired phase shifters (PSs) and switches. For this system, ﬁrst we 11 determine the required number of radio frequency (RF) chains 12 and PSs such that the proposed HB achieves the same perfor- 13 mance as that of the digital beamforming (DB) which utilizes N 14 (number of transmitter antennas) RF chains. We show that the 15 performance of the DB can be achieved with our HB just by uti- 16 lizing rt RF chains and 2rt (N − rt + 1) PSs, where rt ≤ N is the 17 rank of the combined digital precoder matrices of all subcarriers. 18 Second, we provide a simple and novel approach to reduce the 19 number of PSs with only a negligible performance degradation. 20 Numerical results reveal that only 20−40 PSs per RF chain are 21 sufﬁcient for practically relevant parameter settings. Finally, for 22 the scenario where the deployed number of RF chains (Na) is 23 less than rt , we propose a simple user scheduling algorithm to 24 select the best set of users in each subcarrier. Simulation results 25 validate theoretical expressions, and demonstrate the superiority 26 of the proposed HB design over the existing HB designs in both 27 ﬂat fading and frequency selective channels.
%K ICTEAM
%K ICTEAM/SIGN
%K ICTEAM/COMM
%K ICTEAM
%K ICTEAM/SIGN
%K ICTEAM/COMM
%G Anglais
%J IEEE Transactions on Wireless Communications
%B IEEE Transactions on Wireless Communications
%V 15
%N 5
%P 331-3326
%D 2016
%@ 1536-1276 (ISSN)
%@ 1558-2248 (e-ISSN)
%* peer-reviewed
%D 2016
%U Handle: http://hdl.handle.net/2078.1/176754
%R 10.1109/TWC.2016.2519883
%0 Journal Article
%9 Article de recherche
%A Andreotti, R.
%A Wang, T.
%A Lottici, V.
%A Giannetti, F.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Resource Allocation via Max-Min Goodput Optimization for BIC-OFDMA Systems
%X In this paper, a novel resource allocation (RA) strategy is designed for the downlink of orthogonal frequency division multiple access (OFDMA) networks employing practical modulation and coding under quality of service constraints and retransmission techniques. Compared with previous works, two basic concepts are combined together, namely, i) taking the goodput (GP) as performance metric, and ii) ensuring maximum fairness among users. The resulting RA maximizes thus the GP of the worst user, optimizing subcarrier allocation (SA), per-subcarrier power allocation (PA), and adaptation of modulation and coding (AMC) of the active users, yielding a nonlinear nonconvex mixed optimization problem (OP). The intrinsic demanding difﬁculty of the OP is tackled by iteratively and optimally solving the AMC, PA and SA subproblems, devoting special care to the demanding nonlinear combinatorial SA-OP. First, the optimal (yet computationally complex) solution is found by applying the branch&bound method to the optimal SA solution found in the relaxed domain, and accordingly, it is taken as benchmark. Then, an innovative suboptimal yet efﬁcient solution based on the metaheuristic ant colony optimization (ACO) framework is derived. The proposed RA strategy is corroborated by comprehensive simulations, showing improved performance even at the cost of affordable numerical complexity.
%K ICTEAM
%K ICTEAM/SIGN
%K ICTEAM/COMM
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%V 64
%N 6
%P 2412-2426
%D 2016
%@ 0090-6778 (ISSN)
%@ 1558-0857 (e-ISSN)
%* peer-reviewed
%D 2016
%U Handle: http://hdl.handle.net/2078.1/176753
%R 10.1109/TCOMM.2016.2555311
%0 Journal Article
%9 Article de recherche
%A Nguyen, Trung-Hien
%A Louveaux, Jérôme
%A Gorza, Simon-Pierre
%A Horlin, Francois
%+ Université catholique de Louvain (UCL) - SST/ICTM - Institute of Information and Communication Technologies, Electronics and Applied Mathematics
%T Simple feedforward carrier phase estimation for optical FBMC/OQAM systems
%X Filter-bank multi-carrier based on offset quadrature amplitude modulation (OQAM) has recently been proposed to improve the spectral efficiency of optical fiber communication systems. Unfortunately, it is prone to the laser phase noise (PN) that results in significant inter-subcarrier interference due to the loss of OQAM orthogonality. Based on the analysis of the OQAM constellation obtained at the output of the analysis filter bank, we propose a modified blind phase search algorithm working based on the observation of all subcarriers simultaneously. It efficiently compensates for the PN and incurs a low number of multiplications. The proposed method is analytically derived and numerically validated with 4-, 16-, and 64-OQAM modulations. The impact of the number of subcarriers used per optical channel is also investigated. The results show that up to 256 subcarriers can be utilized with negligible performance degradation. Moreover, the method provides a tolerated linewidth and symbol duration product of 1.4 × 10-4, 2.5 × 10-5, and 6.2 × 10-6 for respective 4-, 16-, and 64-OQAM modulations to limit the SNR penalty to 1 dB at a BER of 10-3.
%G Anglais
%J IEEE Photonics Technology Letters
%B IEEE Photonics Technology Letters
%V 28
%N 24
%P 2823-2826
%D 2016
%@ 1041-1135 (ISSN)
%@ 1941-0174 (e-ISSN)
%D 2016
%U Handle: http://hdl.handle.net/2078.1/207297
%R 10.1109/lpt.2016.2623946
%0 Journal Article
%9 Article de recherche
%A He, Ruisi
%A Renaudin, Olivier
%A Kolmonen, Veli-Matti
%A Haneda, Katsuyuki
%A Zhong, Zhangdui
%A Ai, Bo
%A Hubert, Simon
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Vehicle-to-Vehicle Radio Channel Characterization in Crossroad Scenarios
%X Vehicle-to-vehicle (V2V)-communication-based collision avoidance systems detect if two vehicles are on a collision course (e.g., in crossroads, intersections, and highway merging), and they are particularly useful in the absence of line of sight (LOS) owing to buildings, roadside infrastructures, and road bending. Relying on radio measurements using a 4 × 30 multiple-input-multiple-output (MIMO) system at 5.3 GHz, this paper presents the results of an empirical study of V2V propagation channels in two suburban crossroad scenarios, where vehicles are either moving in the same direction and separate from each other along different roads or pass each other in opposite directions at the crossing. The quasi-stationarity interval is first characterized using correlation matrix distance (CMD). Small-scale fading follows a Nakagami distribution based on the Akaike information criteria (AIC). Delay and angular dispersions are found to be significantly affected by the type of crossroad and the presence of an LOS. Cross-correlation coefficients between delay dispersion, angular dispersion, and small-scale fading behavior are also evaluated. By comparing the results of the different crossroads, it is found that the delay and angular dispersions are large in the first type of crossroad. By contrast, in the second type of crossroad, small delay and angular dispersions are observed due to road bending and obstruction by roadside trees.
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%V 65
%N 8
%P 5850-5861
%D 2016
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2016
%U Handle: http://hdl.handle.net/2078.1/177101
%R 10.1109/TVT.2015.2473687
%0 Journal Article
%9 Article de recherche
%A Pasquero, Oudomsack Pierre
%A Rosini, Ramona
%A DaErrico, Raffaele
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T A Correlation Model for Nonstationary Time-Variant On-Body Channels
%X The temporal variation of spatial correlation between on-body radio links is empirically characterized for different walking scenarios. Nonstationary behaviors are highlighted, and a model is proposed for the long-term fading correlation.
%K ICTEAM:COMM
%G Anglais
%J IEEE Antennas and Wireless Propagation Letters
%B IEEE Antennas and Wireless Propagation Letters
%V 14
%N 14
%P 1294-1297
%D 2015
%@ 1536-1225 (ISSN)
%@ 1548-5757 (e-ISSN)
%* peer-reviewed
%D 2015
%U Handle: http://hdl.handle.net/2078.1/166757
%R 10.1109/LAWP.2015.2403237
%0 Journal Article
%9 Article de recherche
%A He, Ruisi
%A Renaudin, Olivier
%A Kolmonen, Veli-Matti
%A Haneda, Katsuyuki
%A Zhong, Zhangdui
%A Ai, Bo
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T A Dynamic Wideband Directional Channel Model for Vehicle-to-Vehicle Communications
%X Vehicle-to-vehicle (V2V) communications have received a lot of attention due to their numerous applications in traffic safety. The design, testing, and improvement of the V2V system hinge critically on the understanding of the propagation channels. An important feature of the V2V channel is the time variance. To statistically model the time-variant V2V channels, a dynamic wideband directional channel model is proposed in this paper, based on measurements conducted at 5.3 GHz in suburban, urban, and underground parking environments. The model incorporates both angular and delay domain properties and the dynamic evolution of multipath components (MPCs). The correlation matrix distance is used to determine the size of local wide-sense stationary (WSS) region. Within each WSS time window, MPCs are extracted using the Bartlett beamformer. A multipath distance-based tracking algorithm is used to identify the “birth” and “death” of such paths over different stationarity regions, and the lifetime of MPC is modeled with a truncated Gaussian distribution. Distributions for the number of multipaths and their positions are statistically modeled. Within each path lifetime, the initial power is found to depend on the excess delay, and a linear polynomial function is used to model the variations within the lifetime. In addition, a Nakagami distribution is suggested to describe the fading behavior. Finally, the model implementation is validated by comparison of second-order statistics between measurements and simulations.
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Industrial Electronics
%B IEEE Transactions on Industrial Electronics
%V 62
%N 12
%P 7870-7882
%D 2015
%@ 0278-0046 (ISSN)
%@ 1557-9948 (e-ISSN)
%* peer-reviewed
%D 2015
%U Handle: http://hdl.handle.net/2078.1/167106
%R 10.1109/TIE.2015.2459376
%0 Journal Article
%9 Article de recherche
%A He, Ruisi
%A Renaudin, Olivier
%A Kolmonen, Veli-Matti
%A Haneda, Katsuyuki
%A Zhong, Zhangdui
%A Ai, Bo
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Characterization of Quasi-Stationarity Regions for Vehicle-to-Vehicle Radio Channels
%X We analyze the nonwide-sense-stationarity (nonWSS) of vehicle-to-vehicle (V2V) radio channels using three metrics: 1) the correlation matrix distance (CMD); 2) the wideband spectral divergence (SD); and 3) the shadow fading correlation. The analysis is based on measurements carried out at 5.3 GHz using a 30 × 4 MIMO system in suburban, urban, and underground parking areas. Several factors such as the existence of a line-of-sight (LOS), the speed of cars, and the antenna array size and configuration are considered in the analysis of non-WSS. It is found that quasi-stationarity region ranges from 3 to 80 m in different V2V scenarios, and is strongly affected by the above factors. Based on the comparison of the equivalent quasi-stationarity region size estimated by the three metrics, it is suggested to use SD and shadowing correlation metrics for systems with small electrical array apertures and to use CMD metric only for arrays with large electrical apertures.
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%V 63
%N 5
%P 2237-2251
%D 2015
%@ 0018-926X (ISSN)
%@ 1558-2221 (e-ISSN)
%* peer-reviewed
%D 2015
%U Handle: http://hdl.handle.net/2078.1/167069
%R 10.1109/TAP.2015.2402291
%0 Journal Article
%9 Article de recherche
%A Soussi, M.E.
%A Zaidi, A.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T DF-based sum-rate optimization for multicarrier multiple access relay channel
%X We consider a system that consists of two sources, a half-duplex relay and a destination. The sources want to transmit their messages reliably to the destination with the help of the relay. We study and analyze the performance of a transmission scheme in which the relay implements a decode-and-forward strategy. We assume that all the channels are frequency selective, and in order to cope with that, we incorporate Orthogonal Frequency-Division Multiplexing (OFDM) transmission into the system. In contrast to previous works, both sources can transmit their messages using all subcarriers and the relay can decide to help none, only one, or both sources. For this scheme, we discuss the design criteria and evaluate the achievable sum-rate. Next, we study and solve the problem of resource allocation aiming at maximizing the achievable sum-rate. We propose an iterative coordinate-descent algorithm that finds a solution that is at least a local optimum. We show through numerical examples the effectiveness of the algorithms and illustrate the benefits of allowing both sources to transmit on all subcarriers. © 2015, El Soussi et al.; licensee Springer.
%K Decode-and-forward
%K OFDM
%K Optimization
%K Relay channel
%K ICTEAM:SIGN
%K ICTEAM:COMM
%G Anglais
%J Eurasip Journal on Wireless Communications and Networking
%B Eurasip Journal on Wireless Communications and Networking
%V 2015
%N 1
%P 1-5
%D 2015
%@ 1687-1472 (ISSN)
%@ 1687-1499 (e-ISSN)
%* peer-reviewed
%D 2015
%U Handle: http://hdl.handle.net/2078.1/162520
%R 10.1186/s13638-015-0361-y
%0 Journal Article
%9 Article de recherche
%A Vinogradov, Evgenii
%A Joseph, Wout
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Measurement-Based Modeling of Time-Variant Fading Statistics in Indoor Peer-to-Peer Scenarios
%X Investigation of small-scale fading in indoor peer-to-peer networks based on radio channel measurements shows that Rayleigh or double Rayleigh (DR) fading with or without line-of-sight (LOS) component can occur, depending on the mobility and on the scattering properties of the environment. While in double-mobile scenarios, the predominant fading mechanism is a combination of Rayleigh and DR fading, Rician fading and fading events caused by the combination of a constant term with a DR component are also occasionally observed. In single-mobile scenarios, temporal fading is Rician or Rayleigh distributed. Additionally, measurements reveal that fading statistics evolve significantly over time, even for small-scale motions of the nodes. We model the transitions between the fading states by means of a hidden Markov model, parameterized from our measurements. Eventually, we propose a complete simulation model that generates channel realizations by combining measurement-based first-order statistics with geometry-based second-order statistics for both types of node mobility.
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%V 63
%N 5
%P 2252-2263
%D 2015
%@ 0018-926X (ISSN)
%@ 1558-2221 (e-ISSN)
%* peer-reviewed
%D 2015
%U Handle: http://hdl.handle.net/2078.1/166758
%R 10.1109/TAP.2015.2403412
%0 Journal Article
%9 Article de recherche
%A Stupia, Ivan
%A Sanguinetti, L.
%A Bacci, G.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Power Control in Networks with Heterogeneous Users: A Quasi-Variational Inequality Approach
%X This paper deals with the power allocation problem in a multipoint-to-multipoint network, which is heterogenous in the sense that each transmit and receiver pair can arbitrarily choose whether to selfishly maximize its own rate or energy efficiency. This is achieved by modeling the transmit and receiver pairs as rational players that engage in a noncooperative game in which the utility function changes according to each player's nature. The underlying game is reformulated as a quasi variational inequality (QVI) problem using convex fractional program theory. The equivalence between the QVI and the noncooperative game provides us with all the mathematical tools to study the uniqueness of its Nash equilibrium points and to derive novel algorithms that allow the network to converge to these points in an iterative manner, both with and without the need for a centralized processing. Numerical results are used to validate the proposed solutions in different operating conditions. © 2015 IEEE.
%K Centralized power control
%K Distributed power control
%K Energy efficiency maximization
%K Heterogeneous users
%K Nash equilibria
%K Quasi-variational inequality
%K Spectral efficiency maximization
%K ICTEAM:SIGN
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%V 63
%N 21
%P 5691-5705
%D 2015
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2015
%U Handle: http://hdl.handle.net/2078.1/167121
%R 10.1109/TSP.2015.2452231
%0 Journal Article
%9 Article de recherche
%A He, Ruisi
%A Zhong, Zhangdui
%A Ai, Bo
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Shadow Fading Correlation in High-Speed Railway Environments
%X In the design of diversity and fast handover schemes for high-speed railways (HSRs), a better understanding of the shadow fading correlation properties is required. In this paper, both auto- and cross-correlation models of shadow fading in HSR environments are proposed based on a large set of measurements with 6146 cells in China. The measurements are conducted using a practically deployed and operative Global System for Mobile Communications-Railway (GSM-R) system at 930 MHz to reflect the real conditions of shadow fading in HSR environments. Seven typical HSR environments and the realistic base station (BS) parameters are considered in the analysis. It is found that the decorrelation distance is correlated with the standard deviation (STD) of shadow fading and is generally larger than 100 m in most HSR environments. The cross correlation of shadow fading between two neighboring BSs depends on the BS height and the tilt angle of the antenna, and a heuristic truncated Gaussian distribution model of cross correlation is proposed. The model is validated by the measurements conducted in another operative HSR line. The results can be used to exploit the simulation algorithms to analyze the signal-to-interference-ratio (SIR) properties and to develop new and better handover schemes for HSRs.
%K ICTM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%V 64
%N 7
%P 2762-2772
%D 2014
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2015
%U Handle: http://hdl.handle.net/2078.1/166756
%R 10.1109/TVT.2014.2351579
%0 Journal Article
%9 Article de recherche
%A Bogale, T.E.
%A Vandendorpe, Luc
%A Le, L.B.
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Wide-band sensing and optimization for cognitive radio networks with noise variance uncertainty
%X This paper considers wide-band spectrum sensing and optimization for cognitive radio (CR) networks with noise variance uncertainty. It is assumed that the considered wide-band contains one or more white sub-bands. Under this assumption, we consider throughput maximization of the CR network while appropriately protecting the primary network. We address this problem as follows. First, we propose novel ratio based test statistics for detecting the edges of each sub-band. Second, we employ simple energy comparison approach to choose one reference white sub-band. Third, we propose novel generalized energy detector (GED) for examining each of the remaining sub-bands by exploiting the noise information of the reference white sub-band. Finally, we optimize the sensing time (T-{o} ) to maximize the CR network throughput using the detection and false alarm probabilities of the GED. The proposed GED does not suffer from signal to noise ratio (SNR wall and outperforms the existing signal detectors. Moreover, the relationship between the proposed GED and conventional energy detector (CED is quantified analytically. We show that the optimal T-{o} depends on the noise variance information. In particular, with 10TV bands, hbox{SNR}=-20 hbox{dB} and 2s frame duration, we found that the optimal T-{o} is 28.5 ms (50.6 ms) with perfect (imperfect) noise variance scenario. © 1972-2012 IEEE.
%K Edge detection
%K Sensing Throughput tradeoff
%K SNR wall
%K Spectrum sensing
%K Wideband cognitive radio
%K ICTEAM:SIGN
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%V 63
%N 4
%P 1091-1105
%D 2015
%@ 0090-6778 (ISSN)
%@ 1558-0857 (e-ISSN)
%* peer-reviewed
%D 2015
%U Handle: http://hdl.handle.net/2078.1/162519
%R 10.1109/TCOMM.2015.2394390
%0 Journal Article
%9 Synthèse de littérature
%A Cotton, Simon
%A D'Errico, Raffaele
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T A review of radio channel models for bodycentric communications
%X The human body is an extremely challenging environment for the operation of wireless communications systems, not least because of the complex antenna-body electromagnetic interaction effects which can occur. This is further compounded by the impact ofmovement and the propagation characteristics of the local environment which all have an effect upon body centric communications channels. As the successful design of body area networks (BANs) and other types of body centric system is inextricably linked to a thorough understanding of these factors, the aim of this paper is to conduct a survey of the current state of the art in relation to propagation and channel models primarily for BANs but also considering other types of body centric communications.We initially discuss some of the standardization efforts performed by the Institute of Electrical and Electronics Engineers 802.15.6 task group before focusing on the two most popular types of technologies currently being considered for BANs, namely narrowband and Ultrawideband (UWB) communications. For narrowband communications the applicability of a generic path loss model is contended, before presenting some of the scenario specific models which have proven successful. The impacts of human body shadowing and small-scale fading are also presented alongside some of the most recent research into the Doppler and time dependencies of BANs. For UWB BAN communications, we again consider the path loss as well as empirical tap delay line models developed from a number of extensive channel measurement campaigns conducted by research institutions around the world. Ongoing efforts within collaborative projects such as Committee on Science and Technology Action IC1004 are also described. Finally, recent years have also seen significant developments in other areas of body centric communications such as off-body and body-to-body communications. We highlight some of the newest relevant research in these areas as well as discussing some of the advanced topics which are currently being addressed in the field of body centric communications.
%K ICTEAM:COMM
%G Anglais
%J Radio Science
%B Radio Science
%V 49
%N 6
%P 371-388
%D June 2014
%@ 0048-6604 (ISSN)
%@ 1944-799X (e-ISSN)
%* peer-reviewed
%D 2014
%U Handle: http://hdl.handle.net/2078.1/146953
%R 10.1002/2013RS005319
%0 Journal Article
%9 Article de recherche
%A El Soussi, Mohieddine
%A Zaidi, Abdellatif
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Compute-and-Forward on a Multi-User Multi-Relay Channel
%X In this paper, we consider a system in which multiple users communicate with a destination with the help of multiple half-duplex relays. Based on the compute-and-forward scheme, each relay, instead of decoding the users' messages, decodes an integer-valued linear combination that relates the transmitted messages. Then, it forwards the linear combination towards the destination. Given these linear combinations, the destination may or may not recover the transmitted messages since the linear combinations are not always full rank. Therefore, we propose an algorithm where we optimize the precoding factor at the users such that the probability that the equations are full rank is increased and that the transmission rate is maximized. We show, through some numerical examples, the effectiveness of our algorithm and the advantage of performing precoding allocation at the users. Also, we show that this scheme can outperform standard relaying techniques in certain regimes.
%G Anglais
%J I E E E Wireless Communications Letters
%B I E E E Wireless Communications Letters
%V 3
%N 6
%P 589 - 592
%D October 2014
%@ 2162-2337 (ISSN)
%@ 2162-2345 (e-ISSN)
%* peer-reviewed
%D 2014
%U Handle: http://hdl.handle.net/2078.1/152119
%R 10.1109/LWC.2014.2362927
%0 Journal Article
%9 Article de recherche
%A El Soussi, Mohieddine
%A Zaidi, Abdellatif
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Compute-and-forward on a multiaccess relay channel: Coding and symmetric-rate optimization
%X We consider a system in which two users communicate with a destination with the help of a half-duplex relay. Based on the compute-and-forward scheme, we develop and evaluate the performance of coding strategies that are of network coding spirit. In this framework, instead of decoding the users' information messages, the destination decodes two integer-valued linear combinations that relate the transmitted codewords. Two decoding schemes are considered. In the first one, the relay computes one of the linear combinations and then forwards it to the destination. The destination computes the other linear combination based on the direct transmissions. In the second one, accounting for the side information available at the destination through the direct links, the relay compresses what it gets using lattice-based Wyner-Ziv compression and conveys it to the destination. The destination then computes the two linear combinations, locally. For both coding schemes, we discuss the design criteria, and derive the allowed symmetric-rate. Next, we address the power allocation and the selection of the integer-valued coefficients to maximize the offered symmetric-rate; an iterative coordinate descent method is proposed. The analysis shows that the first scheme can outperform standard relaying techniques in certain regimes, and the second scheme, while relying on feasible structured lattice codes, can at best achieve the same performance as regular compress-and-forward for the multiaccess relay network model that we study. The results are illustrated through some numerical examples. © 2002-2012 IEEE.
%G Anglais
%J IEEE Transactions on Wireless Communications
%B IEEE Transactions on Wireless Communications
%V 13
%N 4
%P 1932-1947
%D 2014
%@ 1558-2248 (e-ISSN)
%@ 1536-1276 (ISSN)
%* peer-reviewed
%D 2014
%U Handle: http://hdl.handle.net/2078.1/160278
%R 10.1109/TWC.2014.022614.130502
%0 Journal Article
%9 Article de recherche
%A Jin, Zhiwen
%A Wang, Tao
%A Wei, Jibo
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Distributed algorithms for sum rate maximization in multi-cell downlink OFDMA with opportunistic DF relaying
%X This paper considers a multi-cell orthogonal frequency division multiple access (OFDMA) downlink system with several decode-and-forward (DF) relay stations (RSs) aiding the base station (BS) transmissions. The problem considered is the maximization of the system sum rate with a total power constraint in each cell. An iterative semi-distributed resource allocation (RA) algorithm is first proposed to optimize mode selection (decision whether relaying should be used or not and which relay), subcarrier assignment (MSSA), and power allocation (PA), alternatively. During the MSSA stage, the problem is decoupled into subproblems which can be solved distributively in linear time. During the PA stage, an algorithm based on single condensation and Lagrange duality (SCLD) is designed to optimize PA with the tentative MSSA results. The convergence of the SCLD-based RA algorithm is theoretically guaranteed and an local optimum is reached after convergence. To solve the formulated problem autonomously, a modified iterative water-filling (IWF) algorithm is further proposed. Specifically, each cell autonomously optimizes its own sum rate with the estimated power values of the received interferences from the other cells. An optimum algorithm is proposed to solve the local RA problem in each cell. Through numerical experiments, the convergence of the two proposed algorithms as well as their benefits compared with a centralized algorithm (CA) are illustrated.
%G Anglais
%J Eurasip Journal on Wireless Communications and Networking
%B Eurasip Journal on Wireless Communications and Networking
%V 2014
%N 1
%P 1-20
%D 2014
%@ 1687-1472 (ISSN)
%@ 1687-1499 (e-ISSN)
%* peer-reviewed
%D 2014
%U Handle: http://hdl.handle.net/2078.1/160420
%R 10.1186/1687-1499-2014-154
%0 Journal Article
%9 Article de recherche
%A Bogale, Tadilo Endeshaw
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Max-min SNR signal energy based spectrum sensing algorithms for cognitive radio networks with noise variance uncertainty
%X This paper proposes novel spectrum sensing algorithms for cognitive radio networks. By assuming known transmitter pulse shaping filter, synchronous and asynchronous receiver scenarios have been considered. For each of these scenarios, the proposed algorithm is explained as follows: First, by introducing a combiner vector, an over-sampled signal of total duration equal to the symbol period is combined linearly. Second, for this combined signal, the Signal-to-Noise ratio (SNR) maximization and minimization problems are formulated as Rayleigh quotient optimization problems. Third, by using the solutions of these problems, the ratio of the signal energy corresponding to the maximum and minimum SNRs are proposed as a test statistics. For this test statistics, analytical probability of false alarm (Pf) and detection (Pd) expressions are derived for additive white Gaussian noise (AWGN) channel. The proposed algorithms are robust against noise variance uncertainty. The generalization of the proposed algorithms for unknown transmitter pulse shaping filter has also been discussed. Simulation results demonstrate that the proposed algorithms achieve better Pd than that of the Eigenvalue decomposition and energy detection algorithms in AWGN and Rayleigh fading channels with noise variance uncertainty. The proposed algorithms also guarantee the desired Pf(Pd) in the presence of adjacent channel interference signals. © 2014 IEEE.
%K Adjacent channel interference
%K Rayleigh quotients
%K Spectrum sensing
%K Algorithms
%K Cochannel interference
%K Cognitive radio
%K Eigenvalues and eigenfunctions
%K Nonlinear distortion
%K Pulse shaping circuits
%K Signal detection
%K Signal to noise ratio
%K Cognitive radio
%K Statistical tests
%K Statistics
%K White noise
%K Gaussian noise (electronic)
%K Max-min SNR
%K Noise variance uncertainty
%K Rayleigh quotient
%K Spectrum sensing
%K Adjacent channel interference
%K Max-min
%K Noise variance
%K ICTEAM:COMM
%K ICTEAM:SIGN
%G Anglais
%J IEEE Transactions on Wireless Communications
%B IEEE Transactions on Wireless Communications
%V 13
%N 1
%P 280-290
%D 2014
%@ 1536-1276 (ISSN)
%@ 1558-2248 (e-ISSN)
%* peer-reviewed
%D 2014
%U Handle: http://hdl.handle.net/2078.1/150773
%R 10.1109/TWC.2013.122613.130406
%0 Journal Article
%9 Article de recherche
%A Torrea-Duran, Rodolfo
%A Tsiaflakis, Paschalis
%A Vandendorpe, Luc
%A Moonen, Marc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%+ Université catholique de Louvain (UCL) - SST/ICTM/INMA - Pôle en ingénierie mathématique
%T Neighbor-friendly autonomous power control in wireless heterogeneous networks
%X The widespread deployment of base stations constitutes a promising solution to cope with the ever-increasing wireless data rate demands. However, it also increases the interference levels, especially at the cell-edge. Most interference management techniques assume coordination between base stations, which involves undesired overhead and delays. To solve this problem, we propose a neighbor-friendly autonomous algorithm for power control in wireless heterogeneous networks that protects victim users from neighboring cells through a penalty factor in the power allocation level. We refer to this algorithm as neighbor-friendly iterative waterfilling (NF-IWF). In addition, we propose a low-complexity closed-form version that fixes the penalty factor by assuming a linear approximation of the victim user data rate. In high interference conditions, it can achieve a victim user data rate increase by a factor of 3.5 compared to IWF, 15 compared to soft frequency reuse (SFR), and 60 compared to equal power allocation (EPA) with a marginal decrease of the primary user data rate.
%G Anglais
%J Eurasip Journal on Wireless Communications and Networking
%B Eurasip Journal on Wireless Communications and Networking
%V 2014
%D 2014
%@ 1687-1499 (e-ISSN)
%@ 1687-1472 (ISSN)
%* peer-reviewed
%D 2014
%U Handle: http://hdl.handle.net/2078.1/160276
%R 10.1186/1687-1499-2014-175
%0 Journal Article
%9 Article de recherche
%A Mani, Francesco
%A Vitucci, Enrico M.
%A Quitin, Francois
%A Degli-Esposti, Vittorio
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Parameterization of a Polarimetric Diffuse Scattering Model in Indoor Environments
%X Diffuse or dense multipath components play an important role in determining the polarization behavior of wireless transmission channels. In this communication, we parametrize a polarimetric diffuse scattering model in two indoor environments. Our method relies on the empirical extraction of dense multipaths by means of a high resolution algorithm and on the investigation of the properties of this diffuse component. The analysis reveals that diffuse scattering significantly depolarizes the impinging wave in indoor scenarios, yielding cross-polar discrimination values close to 0 dB.
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%V 62
%N 8
%P 4361-4364
%D 2014
%@ 0018-926X (ISSN)
%@ 1558-2221 (e-ISSN)
%* peer-reviewed
%D 2014
%U Handle: http://hdl.handle.net/2078.1/146952
%R 10.1109/TAP.2014.2322901
%0 Journal Article
%9 Article de recherche
%A Khan, Nizabat
%A Jiang, Tao
%A Grace, David
%A Burr, Alister
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Performance Evaluation of Interference Bound Backhaul Links in High Capacity Wireless Networks
%X An innovative architecture employing wireless backhaul in hierarchical wireless networks is considered in this paper to provide high throughput densities. Multi-beam antennas, combined with aggressive frequency reuse have recently been exploited to increase the throughput density in densely deployed wireless networks. However, large number of narrow beams cause not only co-channel interference but also inter-cell interference. To mitigate this problem, amplitude tapering in multi-beam antennas is investigated in this paper. Results show that tapered beams significantly improve the carrier to interference ratio from 5 to 8 dB and consequently achieve downlink throughput density over 0.65 Gbps/km2. An overall throughput density of 1.2 Gbps/km2 is expected when taking both up- and downlinks into account.
%K ICTEAM:COMM
%G Anglais
%J Wireless Personal Communications
%B Wireless Personal Communications
%V 74
%N 4
%P 1129-1145
%D January 2014
%@ 0929-6212 (ISSN)
%@ 1572-834X (e-ISSN)
%* peer-reviewed
%D 2014
%U Handle: http://hdl.handle.net/2078.1/139157
%R 10.1007/s11277-013-1568-z
%0 Journal Article
%9 Article de recherche
%A Van Caekenberghe, Stijn
%A Bourdoux, André
%A Van der Perre, Liesbet
%A Louveaux, Jérôme
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Preamble-based frequency-domain joint CFO and STO estimation for OQAM-based filter bank multicarrier
%X Filter bank multicarrier systems, similarly to orthogonal frequency division multiplexing (OFDM), are very sensitive to carrier frequency offset (CFO) and symbol timing offset (STO). In this paper, a low-complexity preamble-based joint CFO and STO technique is presented. It is based on a relatively long preamble in order to improve the CFO estimation performance as well as avoid interference coming from the data following this preamble. After CFO and STO correction, the preamble can be reused to estimate the channel. Unlike most current techniques, the CFO and STO estimation occurs in the frequency domain. This allows for a low-complexity estimation with respect to time-domain techniques and, as will be shown by simulations, provide even better performance in a reasonable range. The drawback however is that the estimation range is shorter. Specifically, for large STOs (and to a smaller extent large CFOs), the performance decreases below time-domain estimations. Two versions of the STO estimation technique will be presented, the second one being an approximation of the first one, making it less complex yet also less precise. The performance is assessed by means of computer simulations, testing for both large and small STOs, and compared with existing techniques.
%K Preamble-based estimation
%K Carrier frequency offset
%K Symbol timing offset
%K Filterbank multicarrier
%G Anglais
%J Eurasip Journal on Advances in Signal Processing
%B Eurasip Journal on Advances in Signal Processing
%V 2014
%N 118
%P 2014:118
%D July 2014
%@ 1687-6172 (ISSN)
%@ 1687-6180 (e-ISSN)
%* peer-reviewed
%D 2014
%U Handle: http://hdl.handle.net/2078.1/152251
%R 10.1186/1687-6180-2014-118
%0 Journal Article
%9 Article de recherche
%A Mallat, A.
%A Gezici, S.
%A Dardari, D.
%A Craeye, Christophe
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Statistics of the MLE and approximate upper and lower bounds-Part I: Application to TOA estimation
%X In nonlinear deterministic parameter estimation, the maximum likelihood estimator (MLE) is unable to attain the Cramér-Rao lower bound at low and medium signal-to-noise ratios (SNRs) due the threshold and ambiguity phenomena. In order to evaluate the achieved mean-squared error (MSE) at those SNR levels, we propose new MSE approximations (MSEA) and an approximate upper bound by using the method of interval estimation (MIE). The mean and the distribution of the MLE are approximated as well. The MIE consists in splitting the a priori domain of the unknown parameter into intervals and computing the statistics of the estimator in each interval. Also, we derive an approximate lower bound (ALB) based on the Taylor series expansion of noise and an ALB family by employing the binary detection principle. The accuracy of the proposed MSEAs and the tightness of the derived approximate bounds are validated by considering the example of time-of-arrival estimation.
%K Maximum likelihood estimator
%K Mean-squared error
%K Nonlinear estimation
%K Threshold and ambiguity phenomena
%K Time-of-arrival
%K Upper and lowers bounds
%K ICTEAM
%K SIGN
%K COMM
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%V 62
%N 21
%P 5663-5676
%D 2014
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2014
%U Handle: http://hdl.handle.net/2078.1/152284
%R 10.1109/TSP.2014.2355771
%0 Journal Article
%9 Article de recherche
%A Mallat, Achraf
%A Gezici, S.
%A Dardari, D.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SSH/IACS - Institute of Analysis of Change in Contemporary and Historical Societies
%T Statistics of the MLE and approximate upper and lower bounds-part II: Threshold computation and optimal pulse design for TOA estimation
%X Threshold and ambiguity phenomena are studied in Part I of this paper where approximations for the mean-squared error (MSE) of the maximum-likelihood estimator are proposed using the method of interval estimation (MIE), and where approximate upper and lower bounds are derived. In this part, we consider time-of-arrival estimation and we employ the MIE to derive closed-form expressions of the begin-ambiguity, end-ambiguity and asymptotic signal-to-noise ratio (SNR) thresholds with respect to some features of the transmitted signal. Both baseband and passband pulses are considered. We prove that the begin-ambiguity threshold depends only on the shape of the envelope of the ACR, whereas the end-ambiguity and asymptotic thresholds only on the shape of the ACR. We exploit the results on the begin-ambiguity and asymptotic thresholds to optimize, with respect to the available SNR, the pulse that achieves the minimum attainable MSE. The results of this paper are valid for various estimation problems.
%K Maximum likelihood estimator
%K Non-linear estimation
%K Optimal signals
%K Threshold and ambiguity phenomena
%K Time-of-arrival
%K Mean-squared-error
%K Nonlinear estimation
%K Optimal signal design
%K Signal-to-noise ratio
%K Threshold and ambiguity phenomena
%K Time-of-arrival
%K Maximum likelihood estimator
%K Mean-squared errors
%K ICTEAM
%K ICTEAM:SIGN
%K ICTEAM:COMM
%K COMM
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%V 62
%N 21
%P 5677-5689
%D 2014
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2014
%U Handle: http://hdl.handle.net/2078.1/152285
%R 10.1109/TSP.2014.2355776
%0 Journal Article
%9 Article de recherche
%A Jin, Zhiwen
%A Wang, Tao
%A Wei, J.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Sum rate maximization for multi-cell downlink OFDMA with subcarrier pair-based opportunistic DF relaying
%X This paper considers multi-cell decode-and-forward (DF) relay-aided orthogonal frequency division multi-access (OFDMA) downlink systems, in which all sources and relays are coordinated by a central controller for resource allocation (RA). The improved subcarrier pair-based opportunistic DF relaying protocol proposed and studied in the IEEE International Conference on Communications, Beijing, 3795-3800, 2008 and IEEE Trans. Signal Process. 61:2512-2524, 2013 is applied. This protocol has a high spectrum efficiency (HSE) in the sense that all unpaired subcarriers are utilized for data transmission during the second time slot (TS). In particular, the sum (over all cells and all destinations) rate maximized problem with a total power constraint in each cell+ is formulated. To solve this problem, an iterative RA algorithm is proposed to optimize mode selection (decision whether the relay should help or not), subcarrier assignment and pairing (MSSAP) and power allocation (PA) in an alternate way. As for the MSSAP stage of each iteration, the formulated problem is decoupled into subproblems with the tentative PA results. Each subproblem can be easily solved by using the optimal results of a linear assignment problem (LAP), which is then solved by the Hungarian Algorithm in polynomial time. As for the PA stage of each iteration, an algorithm based on single-condensation and geometric programming (SCGP) is proposed to optimize PA in polynomial time with the tentative MSSAP results. The proposed algorithm is coordinate ascent (CA)-based and therefore can reach a local optimum in polynomial time. Finally, the convergence and effectiveness of the proposed algorithm, the impact of relay position and total power on the system performance, and the benefits of using subcarrier pairing (SP) and the HSE protocol are illustrated through numerical experiments. © 2014 Jin et al.; licensee Springer.
%K Cochannel interference mitigation
%K OFDMA
%K Opportunistic DF relaying
%K Resource allocation
%K Subcarrier pairing
%K ICTEAM:COMM
%K ICTEAM:SIGN
%G Anglais
%J Eurasip Journal on Wireless Communications and Networking
%B Eurasip Journal on Wireless Communications and Networking
%V 2014
%N volume 2014
%P article 24
%D 2014
%@ 1687-1472 (ISSN)
%@ 1687-1499 (e-ISSN)
%* peer-reviewed
%D 2014
%U Handle: http://hdl.handle.net/2078.1/150774
%R 10.1186/1687-1499-2014-24
%0 Journal Article
%9 Article de recherche
%A Jin, Zhiwen
%A Wang, Tao
%A Wei, J.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Weighted sum of per cell min-rate maximization for multi-cell downlink OFDMA with opportunistic DF relaying
%X This paper considers a multi-cell relay-aided orthogonal frequency division multiple access (OFDMA) downlink system, in which all stations are coordinated by a central controller for resource allocation (RA). The decode-and-forward (DF) protocol with opportunistic relaying (OR) and high spectrum efficiency (HSE) is applied. The problem of maximizing the weighted sum of per cell min-rate (WSMR) with per-cell total power constraints is formulated, and its per-cell maximum fairness property is proven. An iterative RA algorithm is proposed to optimize mode selection (decision whether the relay should help or not), subcarrier assignment (MSSA) and power allocation (PA) alternatively. Each iteration is composed of the MSSA stage and the PA stage. During the MSSA stage, the original problem is decoupled into mixed integer linear programs (MILPs) with the tentative PA results, which can be solved by typical MILP solvers. To solve the MILPs more efficiently in polynomial time, a randomized rounding-based MSSA (RR-MSSA) algorithm and a direct rounding-based MSSA (DR-MSSA) algorithm are further proposed. During the PA stage, an algorithm based on single condensation and geometric programming (SCGP) PA is designed to optimize PA with the tentative MSSA results. The convergence and the per-cell user fairness of the proposed RA algorithm are proven. Finally, the performance of the RA algorithm and the benefits of using OR and the HSE protocol are illustrated through numerical experiments. © 2014 Jin et al.; licensee Springer.
%K Cochannel interference mitigation
%K OFDMA
%K Opportunistic DF relaying
%K Per-cell user fairness
%K Resource allocation
%K ICTEAM
%K ICTEAM:SIGN
%K ICTEAM:COMM
%G Anglais
%J Eurasip Journal on Wireless Communications and Networking
%B Eurasip Journal on Wireless Communications and Networking
%V 2014
%N volume 2014
%P article 71
%D 2014
%@ 1687-1472 (ISSN)
%@ 1687-1499 (e-ISSN)
%* peer-reviewed
%D 2014
%U Handle: http://hdl.handle.net/2078.1/150775
%R 10.1186/1687-1499-2014-71
%0 Journal Article
%9 Article de recherche
%A Zaidi, Abdellatif
%A Shamai (Shitz), Shlomo
%A Piantanida, Pablo
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Bounds on the Capacity of the Relay Channel With Noncausal State at the Source
%X We consider a three-terminal state-dependent relay channel with the channel state available noncausally at only the source. Such a model may be of interest for node cooperation in the framework of cognition, i.e., collaborative signal transmission involving cognitive and noncognitive radios. We study the capacity of this communication model. One principal problem is caused by the relay's not knowing the channel state. For the discrete memoryless (DM) model, we establish two lower bounds and an upper bound on channel capacity. The first lower bound is obtained by a coding scheme in which the source describes the state of the channel to the relay and destination, which then exploit the gained description for a better communication of the source's information message. The coding scheme for the second lower bound remedies the relay's not knowing the states of the channel by first computing, at the source, the appropriate input that the relay would send had the relay known the states of the channel, and then transmitting this appropriate input to the relay. The relay simply guesses the sent input and sends it in the next block. The upper bound accounts for not knowing the state at the relay and destination. For the general Gaussian model, we derive lower bounds on the channel capacity by exploiting ideas in the spirit of those we use for the DM model; and we show that these bounds are optimal for small and large noise at the relay irrespective to the strength of the interference. Furthermore, we also consider a relay model with orthogonal channels from the source to the relay and from the source and relay to the destination in which the source input component that is heard by the relay does not depend on the channel states. We establish a better upper bound for both DM and Gaussian cases and we also characterize the capacity in a number of special cases.
%K ICTEAM
%K ICTEAM:COMM
%K ICTEAM:SIGN
%G Anglais
%J IEEE Transactions on Information Theory
%B IEEE Transactions on Information Theory
%V 59
%N 5
%P 2639-2672
%D 2013
%@ 0018-9448 (ISSN)
%@ 1557-9654 (e-ISSN)
%* peer-reviewed
%D 2013
%U Handle: http://hdl.handle.net/2078.1/127673
%R 10.1109/TIT.2012.2229780
%0 Journal Article
%9 Article de recherche
%A Horlin, F.
%A Fickers, J.
%A Emplit, P.
%A Bourdoux, A.
%A Louveaux, Jérôme
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Dual-polarization OFDM-OQAMfor communications over optical fibers with coherent detection
%X In order to improve the spectral efficiency of coherent optical communication systems, it has recently been proposed to make use of the orthogonal frequency-division multiplexing offset quadrature amplitude modulation (OFDM-OQAM). Multiple optical channels spaced in the frequency domain by the symbol rate can be transmitted orthogonally, even if each channel overlaps significantly in frequency with its two adjacent channels. The solutions proposed until now in the literature unfortunately only address a single polarization communication, and therefore do not benefit from the capacity gain reached when two polarizations are used to transmit independent information signals. The aim of the present paper is to propose a receiver architecture that can decouple the two polarizations. We build an equalizer per channel at twice the symbol rate and optimize it based on the minimum mean square error (MMSE) criterion. We demonstrate the efficiency of the resulting system compared to the Nyquist wavelength-division multiplexing (N-WDM) system both in terms of performance and complexity. We also assess the system sensitivity to transmit synchronization errors and show that system can even work under significant synchronization errors. © 2013 Optical Society of America.
%K Coherent optical communication systems
%K Polarization
%K Orthogonal frequency division multiplexing
%K Information signals
%K Minimum mean square error criterion
%K Offset quadrature amplitude modulations
%K Receiver architecture
%K Single polarization
%K Spectral efficiencies
%K Synchronization error
%K Optical fibers
%K ULB
%K IMEC
%G Anglais
%J Optics Express
%B Optics Express
%V 21
%N 5
%P 6409-6421
%D 2013
%@ 1094-4087 (ISSN)
%* peer-reviewed
%D 2013
%U Handle: http://hdl.handle.net/2078.1/130698
%R 10.1364/OE.21.006409
%0 Journal Article
%9 Article de recherche
%A Lessinnes, Mathieu
%A Dricot, Jean-Michel
%A De Doncker, Philippe
%A Vandendorpe, Luc
%A Horlin, Francois
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Dynamic Resource Allocation for MIMO Cognitive Networks With Low Control Traffic and Low Computational Complexity
%X adio spectrum scarcity hampers the development of new wireless technologies and services. Cognitive radios have been proposed to enable unlicensed (or secondary) users to borrow locally idle bands of the spectrum provided that no significant interference is created for the licensed (or primary) users. Fast adaptation to the changing spectrum availability is naturally a major requirement in such systems. This adaptation consists of detecting the spectrum occupied by the primary users, computing a new resource allocation for the secondary network, and communicating this allocation through the network. In that context, we develop a resource allocation scheme for multi-input–multi-output wireless mesh networks. The proposed algorithm combines low computational complexity and light control traffic thanks to a combination of relevant approximations in the general nonpolynomial-hard allocation problem. The allocation consists of two steps. First, a centralized carrier allocation is performed at a coordinator node based on partial knowledge of the network parameters. Then, each node locally computes its power allocation through simple water-filling algorithms. Numerical results show that compared to state-of-the-art techniques, 10% of the total throughput of the network is sacrificed to reduce the computation time and the control traffic by two orders of magnitude.
%K Cognitive radio
%K proportional fairness
%K resource allocation
%K ICTEAM
%K ICTEAM:COMM
%K ICTEAM:SIGN
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%V 62
%N 4
%P 1732-1740
%D 2013
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2013
%U Handle: http://hdl.handle.net/2078.1/128849
%R 10.1109/TVT.2012.2231708
%0 Journal Article
%9 Article de recherche
%A van Roy, Stephane
%A Quitin, Francois
%A Liu, LingFeng
%A Oestges, Claude
%A Horlin, Francois
%A Dricot, Jean-Michel
%A De Doncker, Philippe
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Dynamic channel modeling for multi-sensor body area networks
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%V 61
%N 4
%P 2200-2208
%D 2013
%@ 0018-926X (ISSN)
%@ 1558-2221 (e-ISSN)
%* peer-reviewed
%D 2013
%U Handle: http://hdl.handle.net/2078.1/127671
%R 10.1109/TAP.2012.2231917
%0 Journal Article
%9 Article de recherche
%A Andreotti, Riccardo
%A Stupia, Ivan
%A Lottici, V.
%A Giannetti, F.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Goodput-Based Link Resource Adaptation for Reliable Packet Transmissions in BIC-OFDM Cognitive Radio Networks
%X Cognitive radio (CR) stands out as a potential cornerstone to break the spectrum gridlock through enabling the coexistence of licensed (primary) and unlicensed (secondary) users in the same bandwidth. This paper deals with a novel link resource adaptation (LRA) strategy to be applied in CR scenarios for reliable packet transmissions based on bit interleaved coded orthogonal frequency division multiplexing (BIC-OFDM). We first formulate the power allocation (PA) problem constrained by both the available power at the secondary transmitter (ST) and the interference tolerable at the primary receivers, aimed at maximizing the offered layer 3 data rate, i.e., the goodput (GP) metric. Then, we derive the optimal PA strategy resorting to the customary Lagrangian dual decomposition (LDD) technique, which, however, like many other conventional numerical methods, exhibits several drawbacks, such as slow convergence and need for parameter tuning. These restrictions are circumvented through the development of a novel iterative yet simple PA algorithm, referred to as successive set reduction (SSR) approach, whose optimality conditions are analytically demonstrated by resorting to the Quasi Variational Inequality (QVI) framework. Based on this PA algorithm, an adaptive modulation and coding (AMC) scheme at the ST is eventually derived. Simulation results over a realistic scenario corroborate the effectiveness of the proposed SSR-based AMC algorithm, highlighting the GP improvements over non-adaptive LRA techniques, besides a remarkable complexity reduction w.r.t. conventional numerical methods.
%K Cognitive radio
%K ICTEAM:COMM
%K ICTEAM:SIGN
%K ICTEAM
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%V 61
%N 9
%P 2267-2281
%D May 2013
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2013
%U Handle: http://hdl.handle.net/2078/127372
%R 10.1109/TSP.2013.2250970
%0 Journal Article
%9 Article de recherche
%A Horlin, François
%A Fickers, Jessica
%A Deleu, Thibault
%A Louveaux, Jérôme
%+ ULB - OPERA
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Interference-free SDMA for FBMC-OQAM
%X Filter-bank multi-carrier (FBMC) modulations have recently been considered for the emerging wireless communication systems as a means to improve the utilization of the physical resources and the robustness to channel time variations. FBMC divides the overall frequency channel in a set of subchannels of bandwidth proportionally decreasing with the number of subchannels. If the number of subchannels is high enough, the bandwidth of each subchannel is small enough to assume that it is approximately flat. On the other hand, space-division multiple access (SDMA) is a recognized technique to support multiple access in the downlink of a multi-user system. The user signals are precoded at the base station equipped with multiple antennas to separate the users in the spatial domain. The application of SDMA to FBMC is unfortunately difficult when the channel is too frequency selective (or when the number of subchannels to too small) to assume flat subchannels. In that case, the system suffers from inter-symbol and inter-subchannel interference, besides the multi-user interference inherent to SDMA. State-of-the art solutions simply neglect the inter-symbol/subchannel interference. This article proposes a new SDMA precoder for FBMC capable of mitigating the three sources of interference. It is constructed per subchannel in order to keep an acceptable complexity and has the structure of a filter applied on each subchannel and its neighbors at twice the symbol rate. Numerical results demonstrate that the precoder can get rid of all the interference present in the system and benefit therefore from the diversity and power gains achievable with multiple antenna systems.
%K Multi-user downlink
%K Filter-bank modulations
%K FBMC-OQAM
%K multiple antenna technologies
%K MIMO SDMA
%K ULB
%G Anglais
%J EURASIP Journal on Advances in Signal Processing 2013
%B EURASIP Journal on Advances in Signal Processing 2013
%V 2013
%N 1
%P 46
%D March, 12 2013
%@ 1687-6180 (ISSN)
%* peer-reviewed
%D 2013
%U Handle: http://hdl.handle.net/2078.1/130701
%R 10.1186/1687-6180-2013-46
%0 Journal Article
%9 Article de recherche
%A Bogale, Tadilo Endeshaw
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Linear transceiver design for downlink multiuser mimo systems: Downlink-interference duality approach
%X This paper considers linear transceiver design for downlink multiuser multiple-input multiple-output (MIMO) systems. We examine different transceiver design problems. We focus on two groups of design problems. The first group is the weighted sum mean-square-error (WSMSE) (i.e., symbol-wise or user-wise WSMSE) minimization problems and the second group is the minimization of the maximum weighted mean-square-error (WMSE) (symbol-wise or user-wise WMSE) problems. The problems are examined for the practically relevant scenario where the power constraint is a combination of per base station (BS) antenna and per symbol (user), and the noise vector of each mobile station is a zero-mean circularly symmetric complex Gaussian random variable with arbitrary covariance matrix. For each of these problems, we propose a novel downlink-interference duality based iterative solution. Each of these problems is solved as follows. First, we establish a new mean-square-error (MSE) downlink-interference duality. Second, we formulate the power allocation part of the problem in the downlink channel as a Geometric Program (GP). Third, using the duality result and the solution of GP, we utilize alternating optimization technique to solve the original downlink problem. For the first group of problems, we have established symbol-wise and user-wise WSMSE downlink-interference duality. These duality are established by formulating the noise covariance matrices of the interference channels as fixed point functions. On the other hand, for the second group of problems, we have established symbol-wise and user-wise MSE downlink- interference duality. These duality are established by formulating the noise covariance matrices of the interference channels as marginally stable (convergent) discrete-time-switched systems. The proposed duality based iterative solutions can be extended straightforwardly to solve many other linear transceiver design problems. We also show that our MSE downlink-interference duality unify all existing MSE duality. In our simulation results, we have observed that the proposed duality based iterative algorithms utilize less total BS power than that of the existing algorithms. © 1991-2012 IEEE.
%K Convex optimization
%K Downlink-uplink duality
%K Fixed point function
%K MSE
%K Multi-user MIMO
%K Algorithms
%K Convex optimization
%K Covariance matrix
%K Iterative methods
%K MIMO systems
%K Multipath propagation
%K Discrete-time-switched system
%K Signal interference
%K Switching systems
%K Design
%K Downlink-interference duality
%K Downlink-uplink duality
%K Fixed point function
%K MSE
%K Multiuser MIMO
%K Discrete-time-switched system
%K Downlink-interference duality
%K ICTEAM
%K ICTEAM:COMM
%K ICTEAM:SIGN
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%V 61
%N 19
%P 4686-4700
%D 2013
%@ 1053-587X (ISSN)
%* peer-reviewed
%D 2013
%U Handle: http://hdl.handle.net/2078.1/134251
%R 10.1109/TSP.2013.2272554
%0 Journal Article
%9 Article de recherche
%A Awan, Zohaib Hassan
%A Zaidi, Abdellatif
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Multiaccess Channel With Partially Cooperating Encoders and Security Constraints
%X We study a special case of Willems’s two-user multiaccess channel with partially cooperating encoders from a security perspective. This model differs from Willems’s setup in that only one encoder, Encoder 1, is allowed to conference; Encoder 2 does not transmit any message, and there is an additional passive eavesdropper from whom the communication should be kept secret. For the discrete memoryless (DM) case, we establish inner and outer bounds on the capacity-equivocation region. The inner bound is based on a combination of Willems’s coding scheme, noise injection, and additional binning that provides randomization for security. For the memoryless Gaussian model, we establish lower and upper bounds on the secrecy capacity. We also show that, under certain conditions, these bounds agree in some extreme cases of cooperation between the encoders. We illustrate our results through some numerical examples.
%K eavesdropping
%K multiaccess channel
%K security
%K wire-tap channel
%K conferencing
%K ICTEAM institute
%G Anglais
%J IEEE Transactions on Information Forensics and Security
%B IEEE Transactions on Information Forensics and Security
%V 8
%N 7
%P 1243-1254
%D July, 2013
%@ 1556-6013 (ISSN)
%@ 1556-6021 (e-ISSN)
%D 2013
%U Handle: http://hdl.handle.net/2078.1/130991
%R 10.1109/TIFS.2013.2263804
%0 Journal Article
%9 Article de recherche
%A Wang, Tao
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T On the Optimum Energy Efficiency for Flat-Fading Channels with Rate-dependent Circuit Power
%X This paper investigates the optimum energy efficiency (EE) and the corresponding spectral efficiency (SE) for a communication link operating over a flat-fading channel. The EE is evaluated by the total energy consumption for transmitting per message bit. Three channel cases are considered, namely static channel with channel state information available at transmitter (CSIT), fast-varying (FV) channel with channel distribution information available at transmitter (CDIT), and FV channel with CSIT. The link's circuit power is modeled as ρ+κφ(R) Watt, where ρ>0 and κ≥0 are two constants and φ(R) is a general increasing and convex function of the transmission rate R≥0. For all the three channel cases, the tradeoff between the EE and SE is studied. It is shown that the EE improves strictly as the SE increases from 0 to the optimum SE, and then strictly degrades as the SE increases beyond the optimum SE. The impact of κ, ρ and other system parameters on the optimum EE and corresponding SE is investigated to obtain insight. Some of the important and interesting results for all the channel cases include: (1) when κ increases the SE corresponding to the optimum EE should keep unchanged if φ(R)=R, but reduced if φ(R) is strictly convex of R; (2) when the rate-independent circuit power ρ increases, the SE corresponding to the optimum EE has to be increased. A polynomial-complexity algorithm is developed with the bisection method to find the optimum SE. The insight is corroborated and the optimum EE for the three cases are compared by simulation results.
%K ata communication energy conservation fading channels polynomial approximation resource allocation telecommunication links
%K ICTEAM
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%V 61
%N 12
%P 4910-4921
%D 2013
%@ 0090-6778 (ISSN)
%* peer-reviewed
%D 2013
%U Handle: http://hdl.handle.net/2078.1/142483
%R 10.1109/TCOMM.2013.111013.130150
%0 Journal Article
%9 Article de recherche
%A Brante, G.
%A Stupia, Ivan
%A Souza, R.D.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Outage Probability and Energy Efficiency of Cooperative MIMO with Antenna Selection
%X This paper compares the energy efficiency of some cooperative MIMO schemes in wireless networks. By energy efficiency we denote the spectral efficiency seen at the receiver normalized by the total energy consumption, which includes the circuitry, the efficiency of the power amplifier, and the transmission rate. We focus on transmit antenna selection (TAS) and switch and stay combining (SSC) at the receiver. The performance of TAS+SSC is compared to that of TAS and maximal ratio combining (MRC), and to that of transmit/receive beamforming using a singular value decomposition (SVD) technique. We derive closed-form outage probability expressions, and analyze the effect of selecting the antenna from the source to optimize the communication with the relay or with the destination. Our results show that selecting the antennas with respect to the destination is in general a better option when the energy consumption is accounted. Moreover, some power allocation strategies are described and the comparison of the schemes in terms of energy efficiency reveals a considerable improvement with the use of TAS+SSC for low to moderate spectral efficiency, while beamforming outperforms the other schemes for high spectral efficiency when the number of antennas at each node is small.
%G Anglais
%J IEEE Transactions on Wireless Communications
%B IEEE Transactions on Wireless Communications
%V 12
%N 11
%P 5896 - 5907
%D 2013
%@ 1536-1276 (ISSN)
%* peer-reviewed
%D 2013
%U Handle: http://hdl.handle.net/2078.1/138717
%R 10.1109/TWC.2013.092413.130413
%0 Journal Article
%9 Article de recherche
%A Chaudhary, Muhammad Hafeez
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Performance of Power-Constrained Estimation in Hierarchical Wireless Sensor Networks
%X In this paper we study estimation in a power-constrained wireless sensor network, where the network is divided into disjoint groups called clusters. The sensors in each cluster observe a random source that is correlated with the sources being observed by the other clusters. Each cluster has a designated cluster head (CH). Estimation of the sources is performed in two time slots: In the first slot, the sensors in each cluster amplify and forward their noisy measurements to the CH that forms a preliminary estimate of the underlying source; and in the second slot, the CHs send a scaled version of their partial estimates to a remote fusion center (FC) that forms the final estimate of the sources. The CHs and the FC use minimum mean square error estimation rule. To minimize the overall estimation distortion, we propose a power scheduling scheme which allocates power to the sensors and the CHs subject to constraints on the transmit powers of the individual clusters and the overall network. We show that when the sources are fully uncorrelated or fully correlated then the solution to the power allocation problem has a computationally favorable structure and is amenable for distributed implementation. However, the partial correlation between the sources leads to coupling of the optimization variables and the power allocation solution requires centralized computation, which may be computationally expensive. To this end, we propose an alternative formulation based on an upper-bound on the distortion function, which leads to a solution that shares characteristics of the fully uncorrelated and correlated cases. Simulation examples illustrate the effectiveness of the proposed power scheduling scheme.
%K ICTEAM:COMM
%K ICTEAM:SIGN
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%V 61
%N 3
%P 724-739
%D 2013
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2013
%U Handle: http://hdl.handle.net/2078.1/121253
%R 10.1109/TSP.2012.2229993
%0 Journal Article
%9 Article de recherche
%A Wang, Tao
%A Fang, Y.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Power Minimization for OFDM Transmission with Subcarrier-Pair Based Opportunistic DF Relaying
%X This paper develops a sum-power minimized resource allocation (RA) algorithm subject to a sum-rate constraint for cooperative orthogonal frequency division modulation (OFDM) transmission with subcarrier-pair based opportunistic decode-and-forward (DF) relaying. The improved DF protocol first proposed in is used with optimized subcarrier pairing. Instrumental to the RA algorithm design is appropriate definition of variables to represent source/relay power allocation, subcarrier pairing and transmission-mode selection elegantly, so that after continuous relaxation, the dual method and the Hungarian algorithm can be used to find an (at least approximately) optimum RA with polynomial complexity. Moreover, the bisection method is used to speed up the search of the optimum Lagrange multiplier for the dual method. Numerical results are shown to illustrate the power-reduction benefit of the improved DF protocol with optimized subcarrier pairing.
%K ICTEAM:COMM
%K ICTEAM:SIGN
%K ICTEAM
%G Anglais
%J IEEE Communications Letters
%B IEEE Communications Letters
%V 17
%N 3
%P 471-474
%D 2013
%@ 1089-7798 (ISSN)
%* peer-reviewed
%D 2013
%U Handle: http://hdl.handle.net/2078.1/126434
%R 10.1109/LCOMM.2013.012313.122159
%0 Journal Article
%9 Article de recherche
%A Zaidi, Abdellatif
%A Awan, Zohaib Hassan
%A Shamai , Shlomo
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Secure Degrees of Freedom of MIMO X-Channels With Output Feedback and Delayed CSIT
%X We investigate the problem of secure transmission over a two-user multi-input multi-output (MIMO) X-channel in which channel state information is provided with one-unit delay to both transmitters (CSIT), and each receiver feeds back its channel output to a different transmitter. We refer to this model as MIMO X-channel with asymmetric output feedback and delayed CSIT. The transmitters are equipped with M antennas each, and the receivers are equipped with N antennas each. For this model, accounting for both messages at each receiver, we characterize the optimal sum secure degrees of freedom (SDoF) region. We show that, in presence of asymmetric output feedback and delayed CSIT, the sum SDoF region of the MIMO X-channel is same as the SDoF region of a two-user MIMO BC with 2M antennas at the transmitter, N antennas at each receiver and delayed CSIT. This result shows that, upon availability of asymmetric output feedback and delayed CSIT, there is no performance loss in terms of sum SDoF due to the distributed nature of the transmitters. Next, we show that this result also holds if only output feedback is conveyed to the transmitters, but in a symmetric manner, i.e., each receiver feeds back its output to both transmitters and no CSIT. We also study the case in which only asymmetric output feedback is provided to the transmitters, i.e., without CSIT, and derive a lower bound on the sum SDoF for this model. Furthermore, we specialize our results to the case in which there are no security constraints. In particular, similar to the setting with security constraints, we show that the optimal sum DoF region of the (M,M,N,N)–MIMO X-channel with asymmetric output feedback and delayed CSIT is same as the DoF region of a two-user MIMO BC with 2M antennas at the transmitter, N antennas at each receiver, and delayed CSIT. We illustrate our results with some numerical examples.
%G Anglais
%J IEEE Transactions on Information Forensics and Security
%B IEEE Transactions on Information Forensics and Security
%V 11
%N 8
%P 1760-1774
%D Nov.
%@ 1556-6013 (ISSN)
%@ 1556-6021 (e-ISSN)
%* peer-reviewed
%D 2013
%U Handle: http://hdl.handle.net/2078.1/134246
%R 10.1109/TIFS.2013.2278936
%0 Journal Article
%9 Article de recherche
%A Liu, Lingfeng
%A Van Roy, Stéphane
%A Quitin, François
%A De Doncker, Philippe
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Statistical characterization and modeling of Doppler spectrum in dynamic on-body channels
%K ICTEAM:COMM
%G Anglais
%J IEEE Antennas and Wireless Propagation Letters
%B IEEE Antennas and Wireless Propagation Letters
%V 12
%N 1
%P 186 - 189
%D 2013
%@ 1536-1225 (ISSN)
%@ 1548-5757 (e-ISSN)
%* peer-reviewed
%D 2013
%U Handle: http://hdl.handle.net/2078.1/127670
%R 10.1109/LAWP.2013.2245094
%0 Journal Article
%9 Article de recherche
%A Wang, T.
%A Glineur, François
%A Louveaux, Jérôme
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SSH/LIDAM/CORE - Center for operations research and econometrics
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%+ Université catholique de Louvain (UCL) - SST/ICTM/INMA - Pôle en ingénierie mathématique
%T Weighted Sum Rate Maximization for Downlink OFDMA with Subcarrier-pair based Opportunistic DF Relaying
%X This paper addresses a weighted sum rate (WSR) maximization problem for downlink OFDMA aided by a decode-and-forward (DF) relay under a total power constraint. A novel subcarrier-pair based opportunistic DF relaying protocol is proposed. Specifically, user message bits are transmitted in two time slots. A subcarrier in the first slot can be paired with a subcarrier in the second slot for the DF relay-aided transmission to a user. In particular, the source and the relay can transmit simultaneously to implement beamforming at the subcarrier in the second slot. Each unpaired subcarrier in either the first or second slot is used for the source's direct transmission to a user. A benchmark protocol, same as the proposed one except that the transmit beamforming is not used for the relay-aided transmission, is also considered. For each protocol, a polynomial-complexity algorithm is developed to find at least an approximately optimum resource allocation (RA), by using continuous relaxation, the dual method, and Hungarian algorithm. Instrumental to the algorithm design is an elegant definition of optimization variables, motivated by the idea of regarding the unpaired subcarriers as virtual subcarrier pairs in the direct transmission mode. The effectiveness of the RA algorithm and the impact of relay position and total power on the protocols' performance are illustrated by numerical experiments. It is shown that for each protocol, it is more likely to pair subcarriers for relay-aided transmission when the total power is low and the relay lies in the middle between the source and user region. The proposed protocol always leads to a maximum WSR equal to or greater than that for the benchmark one, and the performance gain of using the proposed one is significant especially when the relay is in close proximity to the source and the total power is low. Theoretical analysis is presented to interpret these observations.
%K ICTEAM:MATH
%K ICTEAM:DYNA
%K ICTEAM:COMM
%K INMA:PAI-DYSCO
%K INMA:NEWS-158
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%V 61
%N 10
%P 2512-2524
%D May 15 2013
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2013
%U Handle: http://hdl.handle.net/2078.1/127803
%R 10.1109/TSP.2013.2245326
%0 Journal Article
%9 Article de recherche
%A Renaudin, Olivier
%A Kolmonen, Veli-Matti
%A Vainikainen, Pertti
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Wideband Measurement-Based Modeling of Inter-Vehicle Channels in the 5-GHz Band
%X In this paper, we describe a new wideband singleinput– single-output (SISO) channel model for vehicle-to-vehicle (V2V) channels, based on an extensive measurement campaign carried out at 5.2 GHz around Helsinki, Finland, in August 2007. Both the currently well-known non-stationary behavior and the measured characteristics of the V2V channel motivate the use of a geometry-based stochastic channel modeling (GSCM) approach rather than a classical tapped delay line (TDL) approach. For the time-variant contributions stemming from discrete scatterers, the propagation distance can be deterministically estimated (i.e., geometrically), whereas the fading can be modeled as the combination of a distance-decaying process and two stochastic small- and large-scale processes. The complete parameterization of the V2V wideband channel model, the recipe for its implementation, and the analysis of its validity are also provided in this paper.
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%V 62
%N 8
%P 3531-3540
%D October 2013
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2013
%U Handle: http://hdl.handle.net/2078.1/134622
%R 10.1109/TVT.2013.2257905
%0 Journal Article
%9 Article de recherche
%A Mani, Francesco
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T A ray based method to evaluate scattering by vegetation elements
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%V 60
%N 8
%P 4006-4009
%D August 2012
%@ 0018-926X (ISSN)
%@ 1558-2221 (e-ISSN)
%* peer-reviewed
%D 2012
%U Handle: http://hdl.handle.net/2078.1/113348
%R 10.1109/TAP.2012.2201123
%0 Journal Article
%9 Article de recherche
%A Czink, Nicolai
%A Bandemer, Bernd
%A Oestges, Claude
%A Zemen, Thomas
%A Paulraj, Arogyaswami
%+ FTW - FTW
%+ Stanford University - ISL
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Analytical multi-user MIMO channel modeling: subspace alignment matters
%X For a receiver that observes a mixture of desired and interfering multiple-input multiple-output (MIMO) transmissions, not all interference has the same severity: its effect is modulated by the degree of alignment between the eigenspaces of the desired and undesired channel matrices. An analytical channel model is proposed to account for this effect. Two metrics of eigenspace compatibility are studied, and a method to generate channels of a given degree of compatibility is derived. The resulting model is parameterized using radio channel measurement data, and an implementation recipe for immediate use of the model is provided.
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Wireless Communications
%B IEEE Transactions on Wireless Communications
%V 11
%N 1
%P 367-377
%D January 2012
%@ 1536-1276 (ISSN)
%@ 1558-2248 (e-ISSN)
%* peer-reviewed
%D 2012
%U Handle: http://hdl.handle.net/2078.1/108175
%R 10.1109/TWC.2012.010412.110980
%0 Journal Article
%9 Article de recherche
%A Van Laethem, Benjamin
%A Quitin, François
%A Bellens, François
%A Oestges, Claude
%A De Doncker, Philippe
%+ ULB - OPERA
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Correlation for multi-frequency propagation in urban environment
%X The multi-frequency propagation in urban environment is investigated in this letter. An experimental measurement campaign is conducted to simultaneously measure the GSM-900, GSM-1800 and UMTS band of a cellular system in a suburban environment. The shadowing and small-scale fading parameters are extracted, and the correlation of these parameters across the different frequency bands is measured. It is shown that shadowing coeffcients are highly correlated, while small-scale fading is completely uncorrelated between different frequency bands.
%K ICTEAM:COMM
%G Anglais
%J Progress In Electromagnetics Research Letters
%B Progress In Electromagnetics Research Letters
%V 29
%P 151-156
%D January 2012
%@ 1043-626X (ISSN)
%@ 1937-6480 (e-ISSN)
%* peer-reviewed
%D 2012
%U Handle: http://hdl.handle.net/2078.1/111181
%R 10.2528/PIERL11111701
%0 Journal Article
%9 Article de recherche
%A Mani, Francesco
%A Quitin, François
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Directional spreads of dense multipath components in indoor environments: experimental validation of a ray-tracing approach
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%V 60
%N 7
%P 3389-3396
%D July 2012
%@ 0018-926X (ISSN)
%@ 1558-2221 (e-ISSN)
%* peer-reviewed
%D 2012
%U Handle: http://hdl.handle.net/2078.1/113350
%R 10.1109/TAP.2012.2196942
%0 Journal Article
%9 Article de recherche
%A Mallat, Achraf
%A Louveaux, Jérôme
%A Vandendorpe, Luc
%A Di Dio, Mario
%A Luise, Marco
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Discrete fourier transform-based TOA estimation in UWB systems
%K ICTEAM:COMM
%K ICTEAM:SIGN
%G Anglais
%J EURASIP Journal on Wireless Communications and Networking
%B EURASIP Journal on Wireless Communications and Networking
%V 2012
%N 1
%P 3
%D 2012
%@ 1687-1499 (e-ISSN)
%* peer-reviewed
%D 2012
%U Handle: http://hdl.handle.net/2078.1/122055
%R 10.1186/1687-1499-2012-3
%0 Journal Article
%9 Article de recherche
%A Stupia, Ivan
%A Lottici, V.
%A Giannetti, F.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%+ Université de Pise - Communication Dpt
%T Link resource adaptation for multiantenna bit-interleaved coded multicarrier systems
%X The availability of flexible radio interfaces capable of adapting their configuration to the time-varying operating environment is the key response to the demand encountered in modern wireless networks for high data rates under strict quality of service (QoS) constraints. To this end, this paper develops a novel link resource adaptation (LRA) scheme for soft-decoded multiantenna (MIMO) bit interleaved coded orthogonal frequency division multiplexing (BIC-OFDM) transmissions employing automatic repeat request (ARQ) mechanisms. As the first step, a simple link performance evaluation model based on the effective signal-to-noise ratio (SNR) mapping concept is derived in a closed-form expression that it is shown to yield better accuracy than previous techniques. Then, an effective LRA strategy is formulated taking advantage of that framework. The aim is maximizing the goodput (GP) metric, that is to say, the number of information bits delivered without error to the user by unit of time, over the available radio resources, such as the power distribution on the subchannels, coding rate, modulation order and the MIMO configuration. The numerical results demonstrate considerable performance gains compared with nonadaptive transmissions, while keeping the computational complexity at affordable levels in view of the specific structure of the GP objective function. © 2012 IEEE.
%K Automatic repeat request (ARQ)
%K Bit-interleaved coded modulation
%K Good put
%K Multiple inputs
%K Power allocationmultiple-output (MIMO)
%K Orthogonal frequency division multiplexing
%K Quality of service
%K Data communication systems
%K Cross-layer link resource adaptation
%K Goodput
%K Multiple-input
%K Orthogonal frequency division multiplexing (OFDM)
%K Power allocationmultiple-output (MIMO)
%K Automatic repeat request
%K Bit interleaved coded modulation
%K Cross-layer
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%V 60
%N 7
%P 3644-3656
%D 2012
%@ 1053-587X (ISSN)
%* peer-reviewed
%D 2012
%U Handle: http://hdl.handle.net/2078.1/113617
%R 10.1109/TSP.2012.2192110
%0 Journal Article
%9 Article de recherche
%A Chalise, B.K.
%A Vandendorpe, Luc
%A Zhang, Y.D.
%A Amin, M.G.
%+ Villanova State University - EE dpt
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Local CSI based selection beamforming for amplify-and-forward MIMO relay networks
%X We investigate selection beamforming for a cooperative network that consists of a source, a destination, and two amplify-and-forward (AF) relays, which are all equipped with multiple antennas. The transmit and receive beamforming techniques are respectively applied at the source and destination, and the linear processing operator of the selected AF multiple-input multiple-output (MIMO) relay is optimized. We consider that the source has the instantaneous channel state information (CSI) of the channels from the source to relays but no information regarding the CSI of the channels from the relays to the destination. Partial relay selection (PRS) is employed, i.e., the source routes its information signal to the relay which offers better first-hop signal-to-noise ratio (SNR). Considering a Rayleigh fading environment, we derive an exact closed-form expression for the outage probability at the destination. The validity of the outage probability expression has been confirmed with numerical simulations. We also present the asymptotic analysis of the PRS scheme for the considered multiantenna system and derive the expressions of diversity gain. It is shown that, the overall diversity gain is min(min(n r,1n d,n r,2n d),n r,1n s + n r,2n s) where n s, n d, and n r,q are, respectively, the numbers of antennas at the source, destination and the qth relay. For the condition C: min(n r,1n d,n r,2n d)≥n r,1n s + n r,2n s that can be easily met with practically realizable antenna configurations, it is shown that PRS provides the same diversity order as opportunistic relaying (OR). © 1991-2012 IEEE.
%K Amplify-and-forward MIMO relay
%K Beamforming
%K Diversity order
%K Fading environment
%K Information signals
%K Instantaneous channel state informations
%K Linear processing
%K MIMO relay
%K MIMO relay networks
%K Multi-antenna systems
%K Multiple antenna
%K Opportunistic relaying
%K Opportunistic relaying
%K Outage probability
%K Partial relay selections
%K Rayleigh
%K Receive beamforming
%K Signaltonoise ratio (SNR)
%K Antennas
%K Asymptotic analysis
%K Beamforming
%K Communication channels (information theory)
%K MIMO systems
%K Outage probability
%K Probability
%K Rayleigh fading
%K Channel state information
%K Partial relay selection
%K Amplify-and-forward
%K Antenna configurations
%K Closed-form expression
%K Cooperative networks
%K Diversity gain
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%V 60
%N 5
%P 2433-2446
%D 2012
%@ 1053-587X (ISSN)
%* peer-reviewed
%D 2012
%U Handle: http://hdl.handle.net/2078.1/113618
%R 10.1109/TSP.2012.2184535
%0 Journal Article
%9 Article de recherche
%A Quitin, François
%A Oestges, Claude
%A Bellens, Francois
%A Van Roy, Stéphane
%A Horlin, François
%A De Doncker, Philippe
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Model parameterization and validation for specular-diffuse clustered channel models
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%V 60
%N 8
%P 4019-4022
%D August 2012
%@ 0018-926X (ISSN)
%* peer-reviewed
%D 2012
%U Handle: http://hdl.handle.net/2078.1/113349
%R 10.1109/TAP.2012.2201095
%0 Journal Article
%9 Article de recherche
%A Wang, Tao
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - Autre
%T On the SCALE algorithm for multiuser multicarrier power spectrum management
%X This correspondence studies the successive convex approximation for low complexity (SCALE) algorithm, which was proposed to address the weighted sum rate (WSR) maximized dynamic power spectrum management (DSM) problem for multiuser multicarrier systems. To this end, we first revisit the algorithm, and then present geometric interpretation and properties of the algorithm. A geometric programming (GP) implementation approach is proposed and compared with the low-complexity approach proposed previously. In particular, an analytical method is proposed to set up the default lower-bound constraints added by a GP solver. Finally, numerical experiments are used to illustrate the analysis and compare the two implementation approaches. © 1991-2012 IEEE.
%K Cochannel interference mitigation
%K Dynamic spectrum management
%K Geometric interpretation
%K Geometric programming
%K Implementation approach
%K Interference mitigation
%K Low-complexity
%K Multi carrier
%K Multi carrier systems
%K Multi-user
%K Numerical experiments
%K Convex optimization
%K Spectrum management
%K Successive convex approximations
%K Weighted sum-rate
%K Convex optimization
%K Digital subscriber lines
%K Geometry
%K Power control
%K Power spectrum
%K Approximation algorithms
%K Digital subscriber lines
%K Dynamic spectrum management
%K Geometric programming
%K Orthogonal-frequency-division modulation
%K Power control
%K Analytical method
%K Dynamic Power
%K ICTEAM:COMM
%K ICTEAM:SIGN
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%V 60
%N 9
%P 4992-4998
%D 2012
%@ 1053-587X (ISSN)
%* peer-reviewed
%D 2012
%U Handle: http://hdl.handle.net/2078/114977
%R 10.1109/TSP.2012.2199986
%0 Journal Article
%9 Article de recherche
%A Vitucci, Enrico M.
%A Mani, Francesco
%A Degli-Esposti, Vittorio
%A Oestges, Claude
%+ University of Bologna - DEIS
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Polarimetric properties of diffuse scattering from building walls: experimental parameterization of a ray-tracing model
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%V 60
%N 6
%P 2961-2969
%D June 2012
%@ 0018-926X (ISSN)
%* peer-reviewed
%D 2012
%U Handle: http://hdl.handle.net/2078.1/111393
%R 10.1109/TAP.2012.2194683
%0 Journal Article
%9 Article de recherche
%A Chaudhary, Muhammad Hafeez
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Power Constrained Linear Estimation in Wireless Sensor Networks with Correlated Data and Digital Modulation
%X We study the problem of joint quantization and power allocation in wireless sensor networks where spatially distributed sensors observe a Gaussian random source, quantize the resulting noisy observations, and transmit over orthogonal fading channels to a remote fusion center (FC). The role of the FC is to reconstruct the source with minimal distortion using linear minimum mean square error estimation rule. In this paper, we undertake the design of joint quantization and power allocation based on the following optimization problem: minimize the reconstruction distortion for a given total network power consumption. To address this problem, at each sensor node uniform scalar quantization is assumed. Moreover, assuming pseudo-quantization noise model we show that the problem can be solved using a block-coordinate descent type algorithm which iteratively optimizes the quantization bits and the power allocations. The algorithm takes into account the spatial correlation, the observation noise, and the channel quality of the sensors. Numerical and simulation examples corroborate the analytical results. The examples illustrate that the proposed design holds a considerable performance gain compared to a quantization scheme based on uniform power allocation to the sensors.
%K Digital modulation
%K ICTEAM:COMM
%K ICTEAM:SIGN
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%V 60
%N 2
%P 570-584
%D Feb. 2012
%@ 1053-587X (ISSN)
%* peer-reviewed
%D 2012
%U Handle: http://hdl.handle.net/2078.1/91902
%R 10.1109/TSP.2011.2175220
%0 Journal Article
%9 Article de recherche
%A Bogale, Tadilo Endeshaw
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Robust Sum MSE optimization for downlink multiuser MIMO systems with arbitrary power constraint: Generalized duality approach
%X This paper considers linear minimum mean-square-error (MMSE) transceiver design problems for downlink multiuser multiple-input multiple-output (MIMO) systems where imperfect channel state information is available at the base station (BS) and mobile stations (MSs). We examine robust sum mean-square-error (MSE) minimization problems. The problems are examined for the generalized scenario where the power constraint is per BS, per BS antenna, per user or per symbol, and the noise vector of each MS is a zero-mean circularly symmetric complex Gaussian random variable with arbitrary covariance matrix. For each of these problems, we propose a novel duality based iterative solution. Each of these problems is solved as follows. First, we establish a novel sum average mean-square-error (AMSE) duality. Second, we formulate the power allocation part of the problem in the downlink channel as a Geometric Program (GP). Third, using the duality result and the solution of GP, we utilize alternating optimization technique to solve the original downlink problem. To solve robust sum MSE minimization constrained with per BS antenna and per BS power problems, we have established novel downlink-uplink duality. On the other hand, to solve robust sum MSE minimization constrained with per user and per symbol power problems, we have established novel downlink-interference duality. For the total BS power constrained robust sum MSE minimization problem, the current duality is established by modifying the constraint function of the dual uplink channel problem. And, for the robust sum MSE minimization with per BS antenna and per user (symbol) power constraint problems, our duality are established by formulating the noise covariance matrices of the uplink and interference channels as fixed point functions, respectively. We also show that our sum AMSE duality are able to solve other sum MSE-based robust design problems. Computer simulations verify the robustness of the proposed robust designs compared to the nonrobust/naive designs. © 2011 IEEE.
%K Mean-square-error (MSE) duality
%K Minimum mean-square-error (MMSE) and convex optimization
%K Imperfect channel state information
%K Interference channels
%K Iterative solutions
%K Minimization problems
%K Minimum mean square errors (MMSE)
%K Mobile station
%K Multiuser multiple-input multiple-output (MIMO)
%K Multiuser multiple-input multiple-output systems
%K Noise covariance
%K Noise vectors
%K Multiuser multiple-input multiple-output (MIMO)
%K Per-symbol
%K Power allocations
%K Power constraints
%K Power problem
%K Robust
%K Robust designs
%K Transceiver design
%K Uplink channel
%K Zero-mean circularly symmetric complex Gaussian
%K Antennas
%K Robust
%K Computer simulation
%K Convex optimization
%K Covariance matrix
%K Design
%K Mean square error
%K MIMO systems
%K Optimization
%K Problem solving
%K Alternating optimizations
%K Constraint functions
%K Downlink channels
%K Downlink multiuser MIMO systems
%K Fixed point function
%K Geometric program
%K ICTEAM:COMM
%K ICTEAM:SIGN
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%V 60
%N 4
%P 1862-1875
%D 2012
%@ 1053-587X (ISSN)
%* peer-reviewed
%D 2012
%U Handle: http://hdl.handle.net/2078.1/110338
%R 10.1109/TSP.2011.2180899
%0 Journal Article
%9 Article de recherche
%A Bogale, Tadilo Endeshaw
%A Vandendorpe, Luc
%A Chalise, B.K.
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%+ Villanova State University - EE dpt
%T Robust transceiver optimization for downlink coordinated base station systems: Distributed algorithm
%X This paper considers the joint transceiver design for downlink multiuser multiple-input single-output (MISO) systems with coordinated base stations (BSs) where imperfect channel state information (CSI) is available at the BSs and mobile stations (MSs). By incorporating antenna correlation at the BSs and taking channel estimation errors into account, we solve two robust design problems: 1) minimizing the weighted sum of mean-square-error (MSE) with per BS antenna power constraint, and 2) minimizing the total power of all BSs with per user MSE target and per BS antenna power constraints. These problems are solved as follows. First, for fixed receivers, we propose centralized and novel computationally efficient distributed algorithms to jointly optimize the precoders of all users. Our centralized algorithms employ the second-order-cone programming (SOCP) approach, whereas, our novel distributed algorithms use the Lagrangian dual decomposition, modified matrix fractional minimization and an iterative method. Second, for fixed BS precoders, the receivers are updated by the minimum mean-square-error (MMSE) criterion. These two steps are repeated until convergence is achieved. In all of our simulation results, we have observed that the proposed distributed algorithms achieve the same performance as that of the centralized algorithms. Moreover, computer simulations verify the robustness of the proposed robust designs compared to the nonrobust/naive designs. © 2006 IEEE.
%K Distributed optimization and convex optimization
%K Multiuser multiple-input multiple-output (MIMO)
%K Joint transceiver design
%K Lagrangian dual
%K Matrix
%K Minimum mean-square-error
%K Mobile station
%K Multi user multiple input single outputs
%K Multi-user
%K Power constraints
%K Precoders
%K Robust designs
%K Robust transceiver
%K Total power
%K Transceiver optimization
%K Weighted Sum
%K Antennas
%K Base stations
%K Channel state information
%K Computer simulation
%K Convex optimization
%K Design
%K MIMO systems
%K Antenna correlation
%K Optimization
%K Transceivers
%K Algorithms
%K Centralized algorithms
%K Channel estimation errors
%K Computationally efficient
%K Distributed algorithm
%K Fixed receivers
%K Imperfect channel state information
%K ICTEAM:COMM
%K ICTEAM:SIGN
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%V 60
%N 1
%P 337-350
%D 2012
%@ 1053-587X (ISSN)
%* peer-reviewed
%D 2012
%U Handle: http://hdl.handle.net/2078.1/107492
%R 10.1109/TSP.2011.2170167
%0 Journal Article
%9 Article de recherche
%A Awan, Zohaib Hassan
%A Zaidi, Abdellatif
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%+ Université de Marne la Vallée - Equipe signal et communication
%T Secure communication over parallel relay channel
%X We investigate the problem of secure communication over parallel relay channel in the presence of a passive eavesdropper. We consider a four-terminal relay-eavesdropper channel which consists of multiple relay-eavesdropper channels as subchannels. For the discrete memoryless model, we establish outer and inner bounds on the rate-equivocation region. The inner bound allows mode selection at the relay. For each subchannel, secure transmission is obtained through one of two coding schemes at the relay: decoding-and-forwarding the source message or confusing the eavesdropper through noise injection. For the Gaussian memoryless channel, we establish lower and upper bounds on the perfect secrecy rate. Furthermore, we study a special case in which the relay does not hear the source and show that under certain conditions the lower and upper bounds coincide. The results established for the parallel Gaussian relay-eavesdropper channel are then applied to study the fading relay-eavesdropper channel. Analytical results are illustrated through some numerical examples. © 2006 IEEE.
%K Eavesdropping
%K Fading channels
%K Memoryless
%K Memoryless channels
%K Mode selection
%K Noise injection
%K Numerical example
%K Parallel relay channel
%K Perfect secrecy
%K Secrecy
%K Secure communications
%K Secure transmission
%K Parallel relay channels
%K Subchannels
%K Wire-tap channel
%K Channel coding
%K Fading channels
%K Communication
%K Secrecy
%K Wire-tap channel
%K Analytical results
%K Coding scheme
%K Eavesdropping
%K Gaussians
%K Lower and upper bounds
%K ICTEAM:COMM
%K ICTEAM:SIGN
%G Anglais
%J IEEE Transactions on Information Forensics and Security
%B IEEE Transactions on Information Forensics and Security
%V 7
%N 2
%P 359-371
%D 2012
%@ 1556-6013 (ISSN)
%* peer-reviewed
%D 2012
%U Handle: http://hdl.handle.net/2078.1/110339
%R 10.1109/TIFS.2012.2185493
%0 Journal Article
%9 Article de recherche
%A Liu, Lingfeng
%A Poutanen, Juho
%A Quitin, François
%A Haneda, Katsuyuki
%A De Doncker, Philippe
%A Tufvesson, Fredrik
%A Vainikainen, Pertti
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T The COST 2100 MIMO channel model
%X The COST 2100 channel model is a geometry-based stochastic channel model (GSCM) that can reproduce the stochastic properties of multi-link Multiple-Input Mulitple-Output (MIMO) channels over time, frequency and space. By contrast to other popular GSCMs, the COST 2100 approach is generic and flexible, making it suitable to model multi-user or distributed MIMO scenarios. In this paper a concise overview of the COST 2100 channel model is presented. Main concepts are described, together with useful implementation guidelines. Recent developments, including dense multipath components, polarization and multi-link aspects are also discussed.
%K BESTCOM
%K ICTEAM:COMM
%G Anglais
%J IEEE Wireless Communications Magazine
%B IEEE Wireless Communications Magazine
%V 19
%N 6
%P 92-99
%D December 2012
%@ 1536-1284 (ISSN)
%* peer-reviewed
%D 2012
%U Handle: http://hdl.handle.net/2078.1/117956
%R 10.1109/MWC.2012.6393523
%0 Journal Article
%9 Article de recherche
%A Quitin, François
%A Oestges, Claude
%A Panahandeh, Ali
%A Horlin, Francois
%A De Doncker, Philippe
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Tri-polarized MIMO systems in real-world channels: Channel investigation and performance analysis
%X Polarized multi-antenna systems are an effective solution for reducing inter-antenna spacing while still maintaining low inter-antenna correlation. Traditionally, only dual-polarized antenna systems are used for polarized transceivers. In this paper, tri-polarized antenna systems are investigated. Starting from the polarization mechanisms in the wireless propagation channel, it is shown that dual-polarized MIMO systems show high sensitivity to the transmitter and receiver orientation, which may be very critical in practical applications. Tri-polarized MIMO systems are introduced as a solution to obtain a robust MIMO performances, which are independent of the transmitter and receiver orientation. The performances of dual- and tri-polarized MIMO systems are evaluated on real-world measured channels, and the limits of each of these systems is highlighted.
%K ICTEAM:COMM
%G Anglais
%J Physical Communication
%B Physical Communication
%V 5
%N 4
%P 308-316
%D December 2012
%@ 1874-4907 (ISSN)
%@ 1874-4907 (e-ISSN)
%* peer-reviewed
%D 2012
%U Handle: http://hdl.handle.net/2078.1/117969
%R 10.1016/j.phycom.2012.04.004
%0 Journal Article
%9 Article de recherche
%A Panahandeh, Ali
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Tri-polarized spectrum sensing based on an experimental outdoor-to-indoor cognitive-radio scenario
%X Compared to classical spatially separated multiple antenna system, cross-polarized co-located antenna systems are an interesting way to reduce equipment size while reducing the inter-antenna correlation. In this paper the spectrum sensing of a Cognitive Radio (CR) system taking advantage of polarization diversity under Rayleigh fading is investigated and compared to an equivalent system using spatial diversity. This analysis is based on a theoretical formulation applied to a real-world scenario. For this purpose, an outdoor-to-indoor measurement campaign at a frequency of 3.5 GHz is realized, where an indoor secondary user senses the signals received from an outdoor primary base station. The signals received at each antenna are first combined and then applied to an energy detector. The theoretical expressions are simulated in the measurement context. The detection probability behavior as a function of distance between the Primary Transmitter (PTx) and the Secondary Terminal (STE) and the inter-antenna correlation effect on the sensing performance are studied.
%K ICTEAM:COMM
%G Anglais
%J Physical Communication
%B Physical Communication
%V 5
%N 4
%P 317-327
%D December 2012
%@ 1874-4907 (ISSN)
%@ 1874-4907 (e-ISSN)
%* peer-reviewed
%D 2012
%U Handle: http://hdl.handle.net/2078.1/117966
%R 10.1016/j.phycom.2012.04.001
%0 Journal Article
%9 Article de recherche
%A Bogale, Tadilo Endeshaw
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Weighted sum rate optimization for downlink multiuser MIMO coordinated base station systems: Centralized and distributed algorithms
%X This paper considers the joint linear transceiver design problem for the downlink multiuser multiple-input-multiple-output (MIMO) systems with coordinated base stations (BSs). We consider maximization of the weighted sum rate with per BS antenna power constraint problem. We propose novel centralized and computationally efficient distributed iterative algorithms that achieve local optimum to the latter problem. These algorithms are described as follows. First, by introducing additional optimization variables, we reformulate the original problem into a new problem. Second, for the given precoder matrices of all users, the optimal receivers are computed using minimum mean-square-error (MMSE) method and the optimal introduced variables are obtained in closed form expressions. Third, by keeping the introduced variables and receivers constant, the precoder matrices of all users are optimized by using second-order-cone programming (SOCP) and matrix fractional minimization approaches for the centralized and distributed algorithms, respectively. Finally, the second and third steps are repeated until these algorithms converge. We have shown that the proposed algorithms are guaranteed to converge. We also show that the proposed algorithms require less computational cost than that of the existing linear algorithm. All simulation results demonstrate that our distributed algorithm achieves the same performance as that of the centralized algorithm. Moreover, the proposed algorithms outperform the existing linear algorithm. In particular, when each of the users has single antenna, we have observed that the proposed algorithms achieve the global optimum. © 2011 IEEE.
%K Distributed optimization and convex optimization
%K Matrix fractional minimization
%K Global optimum
%K Iterative algorithm
%K Linear algorithms
%K Linear transceiver
%K Local optima
%K Minimum mean-square-errors (MMSE)
%K Multi-user
%K Multi-user MIMO
%K Multiple-input-multiple-output systems
%K Multiuser multiple-input-multiple-output (MIMO)
%K Minimum mean-square-errors (MMSE)
%K Optimal receiver
%K Optimization variables
%K Power constraints
%K Precoders
%K Rate
%K Single antenna
%K Weighted sum-rate
%K Antennas
%K Base stations
%K Channel estimation
%K Multiuser multiple-input-multiple-output (MIMO)
%K Convex optimization
%K Matrix algebra
%K Mean square error
%K Optimization
%K Telecommunication repeaters
%K Algorithms
%K Rate
%K Centralized algorithms
%K Closed-form expression
%K Computational costs
%K Computationally efficient
%K Distributed optimization and convex optimizations
%K ICTEAM:COMM
%K ICTEAM:SIGN
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%V 60
%N 4
%P 1876-1889
%D 2012
%@ 1053-587X (ISSN)
%* peer-reviewed
%D 2012
%U Handle: http://hdl.handle.net/2078.1/110340
%R 10.1109/TSP.2011.2179538
%0 Journal Article
%9 Article de recherche
%A D'orazio, Leandro
%A Sacchi, Claudio
%A Donelli, Massimo
%A Louveaux, Jérôme
%A Vandendorpe, Luc
%+ University of Trento - DISI
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T A Near-Optimum Multiuser Receiver for STBC MC-CDMA Systems Based on Minimum Conditional BER Criterion and Genetic Algorithm-Assisted Channel Estimation
%K ICTEAM:COMM
%G Anglais
%J Eurasip Journal on Wireless Communications and Networking
%B Eurasip Journal on Wireless Communications and Networking
%P Article ID 351494
%D 2011
%@ 1687-1472 (ISSN)
%@ 1687-1499 (e-ISSN)
%* peer-reviewed
%D 2011
%U Handle: http://hdl.handle.net/2078.1/90130
%R 10.1155/2011/351494
%0 Journal Article
%9 Article de recherche
%A Mani, Francesco
%A Quitin, François
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Accuracy of depolarization and delay spread predictions using advanced ray-based modeling in indoor scenarios
%K ICTEAM:COMM
%G Anglais
%J Eurasip Journal on Wireless Communications and Networking
%B Eurasip Journal on Wireless Communications and Networking
%V 2011
%D Juin 2011
%@ 1687-1499 (ISSN)
%* peer-reviewed
%D 2011
%U Handle: http://hdl.handle.net/2078.1/78526
%R 10.1186/1687-1499-2011-11
%0 Journal Article
%9 Article de recherche
%A Liu, Lingfeng
%A Keshmiri, Farshad
%A Craeye, Christophe
%A De Doncker, Philippe
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%+ ULB - OPERA
%T An analytical modeling of polarized time-variant on-body propagation channels with dynamic body scattering
%K ICTEAM:COMM
%G Anglais
%J Eurasip Journal on Wireless Communications and Networking
%B Eurasip Journal on Wireless Communications and Networking
%V 2011
%N 362521
%P 12
%D Mars 2011
%@ 1687-1472 (ISSN)
%* peer-reviewed
%D 2011
%U Handle: http://hdl.handle.net/2078.1/78516
%R 10.1155/2011/362521
%0 Journal Article
%9 Article de recherche
%A Ihalainen, Tero
%A Ikhlef, Aissa
%A Louveaux, Jérôme
%A Renfors, Markku
%+ Tampere University of Technology - TUT
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Channel Equalization for Multi-Antenna FBMC/OQAM Receivers
%X In this paper, the problem of channel equalization in filter bank multicarrier (FBMC) transmission based on the offset quadrature-amplitude modulation (OQAM) subcarrier modulation is addressed. Finite impulse response (FIR) per-subchannel equalizers are derived based on the frequency sampling (FS) approach, both for the single-input multiple-output (SIMO) receive diversity and the multiple-input multiple-output (MIMO) spatially multiplexed FBMC/OQAM systems. The FS design consists of computing the equalizer in the frequency domain at a number of frequency points within a subchannel bandwidth, and based on this, the coefficients of subcarrier-wise equalizers are derived. We evaluate the error rate performance and computational complexity of the proposed scheme for both antenna configurations and compare them with the SIMO/MIMO OFDM equalizers. The results obtained confirm the effectiveness of the proposed technique with channels that exhibit significant frequency selectivity at the subchannel level and show a performance comparable with the optimum minimum mean-square-error equalizer, despite a significantly lower computational complexity. The possibility of tolerating significant subchannel frequency selectivity gives more freedom in the multicarrier system parameterization. For example, it is possible to use significantly wider subcarrier spacing than what is feasible in OFDM, thus relieving various critical design constraints
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%V 60
%N 5
%P 2070-2085
%D Mai 2011
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2011
%U Handle: http://hdl.handle.net/2078.1/90128
%R 10.1109/TVT.2011.2145424
%0 Journal Article
%9 Article de recherche
%A Liu, Lingfeng
%A D'Errico, Raffaele
%A Ouvry, Laurent
%A De Doncker, Philippe
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%+ CEA - LETI
%+ ULB - OPERA
%T Dynamic Channel Modeling at 2.4 GHz for On-Body Area Networks
%X In wireless body area networks, on-body radio propagation channels are typically time-varying, because of the frequent body movements. The dynamic local body scattering dominates the temporal and spatial properties of the on-body channels. The influence varies largely depending on the distribution of the channels and the modes of body movements. In this paper, we present some major achievements on the dynamic onbody channel modeling at 2.4 GHz under the framework of the COST 2100 action. Results of two complementary measurement campaigns are presented: a geometry-based one on a single subject, and a scenario-based one covering different subjects. Statistical models including the Doppler spectrum and the spatial correlation of on-body channels are presented. An analytical model is also introduced to offer a time-space description of the on-body channels, which is validated by the geometry-based measurement campaign.
%K Body area networks
%K on-body channel
%K timevariant channel fading
%K body shadowing
%K channel spatial correlation
%K dynamic body scattering
%K ICTEAM:COMM
%G Anglais
%J Advances in Electronics and Telecommunications
%B Advances in Electronics and Telecommunications
%V 2
%N 4
%P 18-27
%D December 2011
%@ 2081-8580 (ISSN)
%* peer-reviewed
%D 2011
%U Handle: http://hdl.handle.net/2078.1/111592
%0 Journal Article
%9 Article de recherche
%A Jaspar, Xavier
%A Vandendorpe, Luc
%+ ELIA - Elia
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Impact of Variable Length Codes on the Interleaving Gain of Turbo Systems: The Concept of Bounded Spectrum
%X When a telecommunication system is constrained in terms of delay and complexity, it is usually wise to allow some cross-layer cooperation between the source and channel layers. In this context, the success of joint source-channel turbo techniques has been attested several times in the literature, in particular to transmit variable length code (VLC) streams which are very sensitive to error propagation. Capitalizing on previously developed performance upper bounds, this paper investigates whether the VLC can contribute to the interleaving gain of concatenated codes just as a convolutional code with non-catastrophic encoder would. To this end, the important concept of bounded VLC spectrum is introduced and is proved to be a sufficient condition for the VLC to contribute indeed to the interleaving gain. This concept is also proved to be closely related to non-catastrophic VLCs and, under certain assumptions, to the well known concept of statistically synchronizable VLCs.
%K Variable length code
%K Linear code
%K Interleaving gain
%K Bounded VLCspectrum
%K Statistically synchronizable VLC
%K ICTEAM:COMM
%K ICTEAM:SIGN
%G Anglais
%J Ieee transactions on communications
%B Ieee transactions on communications
%V 59
%N 7
%P 1796-1806
%D 2011
%@ 0090-6778 (ISSN)
%* peer-reviewed
%D 2011
%U Handle: http://hdl.handle.net/2078.1/85309
%R 10.1109/TCOMM.2011.053111.080452
%0 Journal Article
%9 Article de recherche
%A Wang, Tao
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Iterative Resource Allocation for Maximizing Weighted Sum Min-Rate in Downlink Cellular OFDMA Systems
%X This paper considers the downlink of a cellular orthogonal frequency division multi-access (OFDMA) system, in which multiple base stations (BSs) are coordinated by a centralized resource allocation algorithm. We address the problem of maximizing the weighted sum of the minimal user rates (WSMR) of coordinated cells subject to a total power constraint at each BS, in terms of jointly optimizing coordinated BSs' subcarrier and power allocation. In particular, the solution of this problem corresponds to a resource allocation that guarantees similar rates to all users in each cell. An iterative algorithm is proposed to optimize the subcarrier allocation and the power allocation alternatively, so that the WSMR keeps increasing until convergence. In each iteration, the subcarrier allocation is updated by solving a mixed integer linear program for each cell, while the power allocation is updated by solving a successive set of convex optimization problems with a duality-based numerical algorithm. The effectiveness of the algorithm is illustrated by numerical experiments.
%K Cochannel interference mitigation
%K Orthogonal- frequency-division multiplexing
%K Resource allocation
%K Spectrum management.
%K 2556
%K ICTEAM:COMM
%G Anglais
%J Ieee transactions on signal processing
%B Ieee transactions on signal processing
%V 59
%N 1
%P 223-234
%D 2011
%@ 1053-587X (ISSN)
%* peer-reviewed
%D 2011
%U Handle: http://hdl.handle.net/2078.1/74598
%R 10.1109/TSP.2010.2078811
%0 Journal Article
%9 Article de recherche
%A Brah, Felix
%A Zaidi, Abdellatif
%A Louveaux, Jérôme
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T On the Lambert-W function for constrained resource allocation in cooperative networks
%X In cooperative networks, a variety of resource allocation problems can be formulated as constrained optimization with system-wide objective, e.g., maximizing the total system throughput, capacity or ergodic capacity, subject to constraints from individual users, e.g., minimum data rate, transmit power limit, and from the system, e.g., power budget, total number of subcarriers, availability of the channel state information (CSI). Most constrained resource allocation schemes for cooperative networks require rigorous optimization processes using numerical methods since closed-form solutions are rarely found. In this article, we show that the Lambert-W function can be efficiently used to obtain closed-form solutions for some constrained resource allocation problems. Simulation results are provided to compare the performance of the proposed schemes with other resource allocation schemes.
%K Resource allocation
%K Cooperative networks
%K QoS
%G Anglais
%J Eurasip Journal on Wireless Communications and Networking
%B Eurasip Journal on Wireless Communications and Networking
%V 2011
%N 2011
%P Article ID 19
%D June 2011
%@ 1687-1472 (ISSN)
%@ 1687-1499 (e-ISSN)
%* peer-reviewed
%D 2011
%U Handle: http://hdl.handle.net/2078.1/136976
%R 10.1186/1687-1499-2011-19
%0 Journal Article
%9 Article de recherche
%A Bogale, Tadilo Endeshaw
%A Chalise, Batu Krishna
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%+ Villanova University, Villanova, PA, USA - Center for Advanced Communications
%T Robust Transceiver Optimization for Downlink Multiuser MIMO Systems
%X This correspondence addresses the joint transceiver design for downlink multiuser multiple-input multiple-output (MIMO) systems, with imperfect channel state information (CSI) at the base station (BS) and mobile stations (MSs). By incorporating antenna correlation at both ends of the channel and taking channel estimation errors into account, we solve two robust design problems: minimization of the weighted sum mean-square-error (MSE) and minimization of the maximum weighted MSE. These problems are solved as follows: first, we establish three kinds of MSE uplink-downlink duality by transforming only the power allocation matrices from uplink channel to downlink channel and vice versa. Second, in the uplink channel, we formulate the power allocation part of each problem ensuring global optimality. Finally, based on the solution of the uplink power allocation and the MSE duality results, for each problem, we propose an iterative algorithm that performs optimization alternatively between the uplink and downlink channels. Computer simulations verify the robustness of the proposed design compared to the nonrobust/naive design.
%K Downlink
%K Duality
%K DESIGN
%K CAPACITY
%K UPLINK
%K Mean-square error
%K Multiple-input multiple-output (MIMO)
%K Multiuser
%K Robust Transceiver design
%K BROADCAST CHANNEL
%K MULTIPLE-ACCESS
%K IMPERFECT CSI
%K DUALITY
%K 2556
%K ICTEAM:COMM
%G Anglais
%J Ieee transactions on signal processing
%B Ieee transactions on signal processing
%V 59
%N 1
%P 446-453
%D 2011
%@ 1053-587X (ISSN)
%* peer-reviewed
%D 2011
%U Handle: http://hdl.handle.net/2078.1/74601
%R 10.1109/TSP.2010.2080269
%0 Journal Article
%9 Article de recherche
%A Wang, Tao
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Sum Rate Maximized Resource Allocation in Multiple DF Relays Aided OFDM Transmission
%X In relay-aided wireless transmission systems, one of the key issues is how to manage the energy resource at the source and each individual relay, to optimize a certain performance metric. This paper addresses the sum rate maximized resource allocation (RA) problem in an orthogonal frequency division modulation (OFDM) transmission system assisted by multiple decode-and-forward (DF) relays, subject to the individual sum power constraints of the source and the relays. In particular, the transmission at each subcarrier can be in either the direct mode without any relay assisting, or the relay-aided mode with one or several relays assisting. We propose two RA algorithms which optimize the assignment of transmission mode and source power for every subcarrier, as well as the assisting relays and the power allocation to them for every relay-aided subcarrier. First, it is shown that the considered RA problem has zero Lagrangian duality gap when there is a big number of subcarriers. In this case, a duality based algorithm that finds a globally optimum RA is developed. Most interestingly, the sensitivity analysis in convex optimization theory is used to derive a closed-form optimum solution to a related convex optimization problem, for which the method based on the Karush-Kuhn-Tucker (KKT) conditions is not applicable. Second, a coordinate-ascent based iterative algorithm, which finds a suboptimum RA but is always applicable regardless of the duality gap of the RA problem, is developed. The effectiveness of these algorithms has been illustrated by numerical experiments.
%K Orthogonal frequency division modulation
%K Resource allocation
%K Decodeand forward
%K Relaying
%K Lagrangian duality gap
%K Dual decompositionmethod
%K Energy efficiency
%K ICTEAM:COMM
%K ICTEAM:SIGN
%G Anglais
%J Ieee journal on selected areas in communications
%B Ieee journal on selected areas in communications
%V 29
%N 8
%P 1559-1571
%D 2011
%@ 0733-8716 (ISSN)
%* peer-reviewed
%D 2011
%U Handle: http://hdl.handle.net/2078.1/87120
%R 10.1109/JSAC.2011.110906
%0 Journal Article
%9 Article de recherche
%A Pätzold, Matthias
%A Oestges, Claude
%A Molisch, Andreas
%+ University of Agder
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%+ USC
%T Trends in Mobile Radio Channels : Modeling, Analysis, and Simulation
%K ICTEAM:COMM
%G Anglais
%J IEEE Vehicular Technology Magazine : connecting the mobile world
%B IEEE Vehicular Technology Magazine : connecting the mobile world
%V 6
%N 2
%P 21-22
%D 2011
%@ 1556-6072 (ISSN)
%* peer-reviewed
%D 2011
%U Handle: http://hdl.handle.net/2078.1/77782
%R 10.1109/MVT.2011.940791
%0 Journal Article
%9 Article de recherche
%A Wang, Tao
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T WSR Maximized Resource Allocation in Multiple DF Relays Aided OFDMA Downlink Transmission
%X This paper considers the weighted sum rate (WSR) maximized resource allocation (RA) constrained by a system sum power in an orthogonal frequency division multiple access (OFDMA) downlink transmission system assisted by multiple decode-and-forward (DF) relays. In particular, multiple relays may cooperate with the source for every relay-aided transmission. A two-step algorithm is proposed to find the globally optimum RA. In the first step, the optimum source/relay power and assisting relays that maximize the rate is found for every combination of subcarrier and destination, assuming a sum power is allocated to the transmission at that subcarrier to that destination in the relay-aided transmission mode and the direct mode, respectively. In the second step, a convex-optimization based algorithm is designed to find the globally optimum assignment of destination, transmission mode and sum power for each subcarrier to maximize the WSR. Combining the RAs found in the two steps, the globally optimum RA can be found. In addition, we show that the optimum RA in the second step can readily be derived when the system sum power is very high. The effectiveness of the proposed algorithm is illustrated by numerical experiments.
%K Convex optimization
%K Cooperative wireless transmission
%K Decode andforward
%K Orthogonal frequency division multiple access
%K Relaying;resource allocation
%K ICTEAM:COMM
%K ICTEAM:SIGN
%G Anglais
%J Ieee transactions on signal processing
%B Ieee transactions on signal processing
%V 59
%N 8
%P 3964-3976
%D 2011
%@ 1053-587X (ISSN)
%* peer-reviewed
%D 2011
%U Handle: http://hdl.handle.net/2078.1/85307
%R 10.1109/TSP.2011.2153196
%0 Journal Article
%9 Article de recherche
%A Fort, Andrew
%A Keshmiri, Farshad
%A Crusats, Gemma Roqueta
%A Craeye, Christophe
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T A Body Area Propagation Model Derived From Fundamental Principles: Analytical Analysis and Comparison With Measurements
%X Using wireless sensors worn on the body to monitor health information is a promising new application. To realize transceivers targeted for these applications, it is essential to understand the body area propagation channel. Several numerical, simulated, and measured body area propagation studies have recently been conducted. While many of these studies are useful for evaluating communication systems, they are not compared against or justified by more fundamental physical models derived from basic principles. This type of comparison is necessary to provide better physical insights into expected propagation trends and to justify modeling choices. To address this problem, we have developed a simple and generic body area propagation model derived directly from Maxwell's equations revealing basic propagation trends away, inside, around, and along the body. We have verified the resulting analytical model by comparing it with measurements in an anechoic chamber. This paper develops an analytical model of the body, describes the expected body area pathloss trends predicted by Maxwell's equations, and compares it with measurements of the electric field close to the body.
%K Body area networks
%K propagation model
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%! IEEE Trans. Antennas Propag.
%V 58
%N 2
%P 503-514
%D 2010
%@ 0018-926X (ISSN)
%@ 1558-2221 (e-ISSN)
%* peer-reviewed
%D 2010
%U Handle: http://hdl.handle.net/2078.1/34189
%R 10.1109/TAP.2009.2025786
%0 Journal Article
%9 Article de recherche
%A Van Roy, Stéphane
%A Oestges, Claude
%A Horlin, Francois
%A De Doncker, Philippe
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%+ Université catholique de Louvain (UCL) - SST/ICTM/INGI - Pôle en ingénierie informatique
%T A Comprehensive Channel Model for UWB Multisensor Multiantenna Body Area Networks
%X Body area networks consist of a number of biological sensors communicating over the air with a central sink placed in close proximity of the human body. A promising solution is to use multisensor multiantenna ultrawideband architecture; each sensor carries one antenna, while the central sink supports an antenna array. In this paper, a complete analytical channel model has been developed for the on-body diffracted waves mechanism. It builds on the existing IEEE 802.15.4a standard channel model and offers an innovative space-time correlation model.
%K Body area networks
%K multisensor multiantenna
%K spatial correlation
%K ultrawideband (UWB)
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%! IEEE Trans. Antennas Propag.
%V 58
%N 1
%P 163-170
%D 2010
%@ 0018-926X (ISSN)
%@ 1558-2221 (e-ISSN)
%* peer-reviewed
%D 2010
%U Handle: http://hdl.handle.net/2078.1/34270
%R 10.1109/TAP.2009.2036280
%0 Journal Article
%9 Article de recherche
%A Bhagavatula, Ramya
%A Oestges, Claude
%A Heath, Robert W.
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T A New Double-Directional Channel Model Including Antenna Patterns, Array Orientation, and Depolarization
%X Multiple-input-multiple-output (MIMO) wireless channel models are often too simplistic to accurately model wireless propagation effects or too complex and/or site specific to be used for analytical purposes. In this paper, we develop a double-directional MIMO channel model that accounts for important propagation effects like scattering, clustering, and channel depolarization and antenna effects like antenna diversity, cross polarization, and random array orientation, while still retaining an intuitive representation. The proposed model can be parameterized using channel measurements obtained from site-specific measurement campaigns or from standard-based channel models. We show, using simulations, that the proposed model captures channel and antenna effects not included in other models, like the third-generation partnership program (3GPP) spatial channel model, the WINNER, and the IEEE 802.11n channel model. We use the model to study the impact of random orientation and channel depolarization on the data rates of a MIMO system.
%K Antenna diversity
%K channel depolarization
%K mobile orientation
%K multiple-input-multiple-output (MIMO) channel modeling
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%! IEEE Trans. Veh. Technol.
%V 59
%N 5
%P 2219-2231
%D 2010
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2010
%U Handle: http://hdl.handle.net/2078.1/33768
%R 10.1109/TVT.2010.2045775
%0 Journal Article
%9 Article de recherche
%A Quitin, Francois
%A Oestges, Claude
%A Horlin, Francois
%A De Doncker, Philippe
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T A Polarized Clustered Channel Model for Indoor Multiantenna Systems at 3.6 GHz
%X Multiple-input-multiple-output (MIMO) technologies allow high data rates to be obtained, but they suffer from interantenna correlation caused by the limits in interantenna spacing. Polarized MIMO systems resolve this problem by using colocated perpendicularly polarized antennas that have low interantenna correlation. In this paper, a polarized single-directional channel model for 2 x N MIMO systems at 3.6 GHz in an indoor environment is presented. The wireless channel is modeled as a sum of clusters, where each cluster has specular and diffuse components. The polarization of the specular component of the clusters is included by considering a per-path polarization. The diffuse component of the clusters is modeled with a Fisher-Bingham (FB5) spectrum in the azimuth-coelevation domain and with an exponential power delay profile. Polarization is analyzed by introducing the cross-polar discrimination of the exponential power delay profile parameters. All of the parameters in the model are extracted from an experimental measurement campaign performed in an indoor environment at 3.6 GHz. Individual paths are extracted from the measurements with the space-alternating generalized expectation-maximization (SAGE) algorithm. These paths are grouped in clusters within the azimuth of arrival-elevation of arrival-delay domains at the receiver side using automatic clustering algorithms. The specular component properties of the clusters are then determined. Finally, the diffuse components of the clusters are investigated and parameterized by applying a beam-forming algorithm on the diffuse part of the impulse response.
%K Channel modeling
%K cluster
%K diffuse multipath component (DMC)
%K multiple-input-multiple-output (MIMO)
%K polarization
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%! IEEE Trans. Veh. Technol.
%V 59
%N 8
%P 3685-3693
%D 2010
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2010
%U Handle: http://hdl.handle.net/2078.1/34967
%R 10.1109/TVT.2010.2064795
%0 Journal Article
%9 Article de recherche
%A Chaudhary, Muhammad Hafeez
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Adaptive Power Allocation in Wireless Sensor Networks with Spatially Correlated Data and Analog Modulation: Perfect and Imperfect CSI
%X We address the problem of power allocation in a wireless sensor network where distributed sensors amplify and forward their partial and noisy observations of a Gaussian random source to a remote fusion center (FC). The FC reconstructs the source based on linear minimum mean-squared error (LMMSE) estimation rule. Motivated by the availability of limited energy in the sensor networks, we undertake the design of power allocation based on minimization of the reconstruction distortion subject to a constraint on the network transmit power. The design is based on the following two cases: (i) exact knowledge of the channel gains and (ii) the estimates of the channel gains. We show that the distortion can be represented as a convex function of the transmit powers of the sensors. Moreover, we show that the power allocation based on this distortion function does not bear any closed form solution. To this end, we propose a novel design based on the successive approximation of the LMMSE distortion, which turns out to be simple, computationally efficient, and exhibits excellent convergence properties. The simulation examples illustrate that the proposed design holds considerable performance gain compared to a uniform power allocation scheme.
%K Power allocation
%K Sensor network
%K Perfect CSI
%K Imperfect CSI
%K 2556
%K ICTEAM:COMM
%G Anglais
%J Eurasip Journal on Wireless Communications and Networking
%B Eurasip Journal on Wireless Communications and Networking
%V 2010
%N 1
%P 14 pages
%D 2010
%@ 1687-1472 (ISSN)
%@ 1687-1499 (e-ISSN)
%* peer-reviewed
%D 2010
%U Handle: http://hdl.handle.net/2078.1/74602
%R 10.1155/2010/817961
%0 Journal Article
%9 Article de recherche
%A Louveaux, Jérôme
%A van der Veen, Alle-Jan
%+ Université catholique de Louvain (UCL) - SST/ICTM - Institute for Information and Communication. Technologies, Electronics and Applied Mathematics
%T Adaptive Precoding for Downstream Crosstalk Precancelation in DSL Systems Using Sign-Error Feedback
%X The performance of many very high bit rate digital subscriber line (VDSL) systems is limited by the effects of crosstalk among the wires in a bundle. For the downstream, a precoder can compensate for this, provided that some crosstalk channel information is available at the transmitter. In this paper, we investigate the issue of precoder design based on a particular type of feedback: it is assumed that each receiver sends back the (complex) sign of the noise on the symbol detection as a way to provide the needed information on crosstalk channels. We derive an algorithm that makes use of this limited information in an adaptive way to iteratively compute the precoder. The performance of the proposed algorithm is extensively analyzed, both with theoretical evaluations and simulation results. The algorithm is also compared to other solutions, showing the efficient performance for the limited amount of overhead it requires.
%K Adaptive algorithm
%K channel estimation
%K crosstalk
%K precoding
%K vectored DSL
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%! IEEE Trans. Signal Process.
%V 58
%N 6
%P 3173-3179
%D 2010
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2010
%U Handle: http://hdl.handle.net/2078.1/33851
%R 10.1109/TSP.2010.2043969
%0 Journal Article
%9 Article de recherche
%A Herzet, Cedric
%A Woradit, Kampol
%A Wymeersch, Henk
%A Vandendorpe, Luc
%+ INRIA - Centre Rennes Bretagne Atlantique, Campus universitaire de Beaulieu, Rennes, France
%+ Srinakharinwirot University, Nakonnayok, Thailand - EE dpt
%+ Chalmers University of Technology, Gothenburg, Sweden - Department of Signals and Systems,
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Code-Aided Maximum-Likelihood Ambiguity Resolution Through Free-Energy Minimization
%X In digital communication receivers, ambiguities in terms of timing and phase need to be resolved prior to data detection. In the presence of powerful error-correcting codes, which operate in low signal-to-noise ratios (SNR), long training sequences are needed to achieve good performance. In this contribution, we develop a new class of code-aided ambiguity resolution algorithms, which require no training sequence and achieve good performance with reasonable complexity. In particular, we focus on algorithms that compute the maximum-likelihood (ML) solution (exactly or in good approximation) with a tractable complexity, using a factor-graph representation. The complexity of the proposed algorithm is discussed and reduced complexity variations, including stopping criteria and sequential implementation, are developed.
%K Belief propagation
%K Maximum-likelihood estimation
%K Optimal receivers.
%K 2556
%K ICTEAM:COMM
%G Anglais
%J Ieee transactions on signal processing
%B Ieee transactions on signal processing
%V 58
%N 12
%P 6238-6250
%D 2010
%@ 1053-587X (ISSN)
%* peer-reviewed
%D 2010
%U Handle: http://hdl.handle.net/2078.1/74604
%R 10.1109/TSP.2010.2068291
%0 Journal Article
%9 Article de recherche
%A Zaidi, Abdellatif
%A Kotagiri, Shiva Prasad
%A Laneman, J. Nicholas
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM - Institute for Information and Communication. Technologies, Electronics and Applied Mathematics
%T Cooperative Relaying With State Available Noncausally at the Relay
%X In this paper, we consider a three-terminal state-dependent relay channel (RC) with the channel state noncausally available at only the relay. Such a model may be useful for designing cooperative wireless networks with some terminals equipped with cognition capabilities, i.e., the relay in our setup. In the discrete memoryless (DM) case, we establish lower and upper bounds on channel capacity. The lower bound is obtained by a coding scheme at the relay that uses a combination of codeword splitting, Gel'fand-Pinsker binning, and decode-and-forward (DF) relaying. The upper bound improves upon that obtained by assuming that the channel state is available at the source, the relay, and the destination. For the Gaussian case, we also derive lower and upper bounds on the capacity. The lower bound is obtained by a coding scheme at the relay that uses a combination of codeword splitting, generalized dirty paper coding (DPC), and DF relaying; the upper bound is also better than that obtained by assuming that the channel state is available at the source, the relay, and the destination. In the case of degraded Gaussian channels, the lower bound meets with the upper bound for some special cases, and, so, the capacity is obtained for these cases. Furthermore, in the Gaussian case, we also extend the results to the case in which the relay operates in a half-duplex mode.
%K Channel state information
%K cognitive radio
%K (generalized) dirty paper coding (DPC)
%K relay channel (RC)
%K user cooperation
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Information Theory
%B IEEE Transactions on Information Theory
%! IEEE Trans. Inf. Theory
%V 56
%N 5
%P 2272-2298
%D 2010
%@ 0018-9448 (ISSN)
%@ 1557-9654 (e-ISSN)
%* peer-reviewed
%D 2010
%U Handle: http://hdl.handle.net/2078.1/33823
%R 10.1109/TIT.2010.2043782
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Czink, Nicolai
%A Bandemer, Bernd
%A Castiglione, Paolo
%A Kaltenberger, Florian
%A Paulraj, Arogyaswami J.
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Experimental Characterization and Modeling of Outdoor-to-Indoor and Indoor-to-Indoor Distributed Channels
%X We propose and parameterize an empirical model of the outdoor-to-indoor and indoor-to-indoor distributed (cooperative) radio channel, using experimental data in the 2.4-GHz band. In addition to the well-known physical effects of path loss, shadowing, and fading, we include several new aspects in our model that are specific to multiuser distributed channels: 1) correlated shadowing between different point-to-point links, which has a strong impact on cooperative system performance; 2) different types of indoor node mobility with respect to the transmitter and/or receiver nodes, implying a distinction between static and dynamic shadowing motivated by the measurement data; and 3) a small-scale fading distribution that captures more severe fading than that given by the Rayleigh distribution.
%K Channel measurements
%K cooperative communications
%K distributed networks
%K radio channel modeling
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%! IEEE Trans. Veh. Technol.
%V 59
%N 5
%P 2253-2265
%D 2010
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2010
%U Handle: http://hdl.handle.net/2078.1/33769
%R 10.1109/TVT.2010.2042475
%0 Journal Article
%9 Article de recherche
%A Chalise, Batu K.
%A Vandendorpe, Luc
%+ Villanova University, Villanova, PA, USA - Center for Advanced Communications
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Joint Linear Processing for an Amplify-and-Forward MIMO Relay Channel with Imperfect Channel State Information
%X The problem of jointly optimizing the source precoder, relay transceiver, and destination equalizer has been considered in this paper for a multiple-input-multiple-output (MIMO) amplify-and-forward (AF) relay channel, where the channel estimates of all links are assumed to be imperfect. The considered joint optimization problem is nonconvex and does not offer closed-form solutions. However, it has been shown that the optimization of one variable when others are fixed is a convex optimization problem which can be efficiently solved using interior-point algorithms. In this context, an iterative technique with the guaranteed convergence has been proposed for the AF MIMO relay channel that includes the direct link. It has been also shown that, for the double-hop relay case without the receive-side antenna correlations in each hop, the global optimality can be confirmed since the structures of the source precoder, relay transceiver, and destination equalizer have closed forms and the remaining joint power allocation can be solved using Geometric Programming (GP) technique under high signal-to-noise ratio (SNR) approximation. In the latter case, the performance of the iterative technique and the GP method has been compared with simulations to ensure that the iterative approach gives reasonably good solutions with an acceptable complexity. Moreover, simulation results verify the robustness of the proposed design when compared to the nonrobust design that assumes estimated channels as actual channels.
%K MIMO relay amplify and forward imperfect CSI
%K 2556
%K ICTEAM:COMM
%G Anglais
%J Eurasip journal on advances in signal processing
%B Eurasip journal on advances in signal processing
%V 2010
%N 2
%P 13 pages
%D 2010
%@ 1687-6172 (ISSN)
%* peer-reviewed
%D 2010
%U Handle: http://hdl.handle.net/2078.1/74600
%R 10.1155/2010/640186
%0 Journal Article
%9 Article de recherche
%A Renaudin, Olivier
%A Kolmonen, Veli-Matti
%A Vainikainen, Pertti
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Non-Stationary Narrowband MIMO Inter-Vehicle Channel Characterization in the 5-GHz Band
%X In this paper, we describe measurements and models of 30 x 30 narrowband multiple-input -multiple-output (MIMO) vehicle-to-vehicle (V2V) radio propagation channels at 5.3 GHz. Four environments were considered: a campus, a highway, a suburban area, and an urban area. Since the scattering environment may rapidly change in V2V communications, we first investigate the validity of the wide-sense stationarity (WSS) assumption for such channels using the correlation matrix distance (CMD), which is a metric for the characterization of the MIMO channel non-stationarity. Moreover, statistical channel models were developed for these environments, which take into account the non-stationary behavior of the measured V2V channels. The large-scale fading was found to be lognormally distributed, whereas the small-scale fading was characterized by the flexible Weibull distribution. Finally, the non-stationary behavior of both large-scale fading and small-scale fading statistics was investigated.
%K Channel modeling
%K channel sounding
%K time-variant parameter estimation
%K vehicular radio propagation channels
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%! IEEE Trans. Veh. Technol.
%V 59
%N 4
%P 2007-2015
%D 2010
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2010
%U Handle: http://hdl.handle.net/2078.1/33870
%R 10.1109/TVT.2010.2040851
%0 Journal Article
%9 Article de recherche
%A Guenach, Mamoun
%A Louveaux, Jérôme
%A Vandendorpe, Luc
%A Whiting, Phil
%A Maes, Jochen
%A Peeters, Michael
%+ Université catholique de Louvain (UCL) - SST/ICTM - Institute for Information and Communication. Technologies, Electronics and Applied Mathematics
%T On Signal-to-Noise Ratio-Assisted Crosstalk Channel Estimation in Downstream DSL Systems
%X Downstream (DS) crosstalk channels of digital subscriber line systems can be estimated based on the reported signal-to-noise ratio (SNR). In the case of an already active victim line (VL) impacted by the joining of a new disturber line (DL), sending perturbing signals on the VL and reporting the SNRs allow the estimation of the crosstalk channel from the DL to the VL. This paper generalizes that concept to include full startup, tracking and joining scenarios as well as the impact of different perturbation signal choices. Additionally, the sensitivity of the algorithm to different sources of imperfection is analyzed. Simulation results reveal that starting without precoding, and updating the precoder matrix based on the DS crosstalk channel estimates, the far-end crosstalk-free SNR can be reached in a limited number of iterations (e. g., 36 SNR measurements are needed for the four lines case). The SNR-assisted method is documented in an informative appendix of the draft G. vector recommendation as a backward compatible method for very high speed digital subscriber lines (VDSL2) and, hence, can be used for channel acquisition today.
%K Channel estimation
%K digital subscriber lines (DSLs)
%K vectoring
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%! IEEE Trans. Signal Process.
%V 58
%N 4
%P 2327-2338
%D 2010
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2010
%U Handle: http://hdl.handle.net/2078.1/34071
%R 10.1109/TSP.2010.2040408
%0 Journal Article
%9 Article de recherche
%A Chalise, Batu Krishna
%A Vandendorpe, Luc
%+ Villanova University, Villanova, PA, USA - Center for Advanced Communications
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Optimization of MIMO Relays for Multipoint-to-Multipoint Communications: Nonrobust and Robust Designs
%X In this paper, we propose algorithms to jointly optimize the multiple multiantenna relays which assist multipoint-to-multipoint communications in wireless networks. Assuming that the knowledge of the second order statistics of the channels such as covariance matrices are available, the multiple-input-multiple-output (MIMO) relays are designed using two different methods: (1) minimize the sum of the powers of the relays while fulfilling the signal-to-interference-plus-noise ratio (SINR) requirements for all destinations and (2) maximize the minimum of the SINRs of all destinations satisfying the transmit power constraint of each MIMO relay. Furthermore, considering the fact that the covariance matrices of the channels between the MIMO relays and destinations are subject to uncertainty due to feedback and quantization errors, the robust versions of the aforementioned methods based on worst-case concept are proposed. It is shown that the proposed nonrobust as well as robust designs are nonconvex optimization problems but they can be solved accurately and efficiently using the standard semidefinite relaxation and randomization techniques. Computer simulations verify the improved performance of the robust designs over nonrobust methods.
%K Channel estimation
%K Covariance matrix
%K Covariance matrices
%K Radio links
%K Relays
%K Wireless channels
%K Interference
%K MIMO
%K Quality of service
%K Relays
%K Robustness
%K MIMO communication
%K Antenna arrays
%K Concave programming
%K 2556
%K ICTEAM:COMM
%G Anglais
%J Ieee transactions on signal processing
%B Ieee transactions on signal processing
%V 58
%N 12
%P 6355-6368
%D 2010
%@ 1053-587X (ISSN)
%* peer-reviewed
%D 2010
%U Handle: http://hdl.handle.net/2078.1/74603
%R 10.1109/TSP.2010.2077632
%0 Journal Article
%9 Article de recherche
%A Jaspar, Xavier
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM - Institute for Information and Communication. Technologies, Electronics and Applied Mathematics
%T Performance Bounds and Distance Spectra of Variable Length Codes in Turbo/Concatenated Systems
%X Variable length codes (VLCs), used in data compression, are very sensitive to error propagation in the presence of noisy channels. Addressing this problem with joint source-channel turbo techniques has been proposed in the literature and looks quite promising. But to date, most code-related conclusions are based on simulations. This paper states and proves several theoretical results about the robustness of prefix VLCs concatenated with linear error correcting codes (ECC), assuming a maximum likelihood decoder. Especially, an approximate and asymptotically tight distance spectrum of the concatenated code (VLC+ECC) is rigorously developed. Together with the union bound, it provides upper bounds on the symbol and frame/packet error rates.
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%! IEEE Trans. Commun. (USA)
%V 58
%N 9
%P 2537-2548
%D 2010
%@ 0090-6778 (ISSN)
%* peer-reviewed
%D 2010
%U Handle: http://hdl.handle.net/2078.1/66141
%R 10.1109/TCOMM.2010.09.080451
%Z Jaspar, X.; Vandendorpe, L.; Lab. de Telecommun. et Teledetection,Univ. Catholique de Louvain, Louvain-la-Neuve, Belgium
%0 Journal Article
%9 Article de recherche
%A Quitin, François
%A Oestges, Claude
%A Horlin, Francois
%A De Doncker, Philippe
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T Polarization Measurements and Modeling in Indoor NLOS Environments
%X Cross-polarized antenna systems are an attractive way to reduce equipment size while maintaining low inter-antenna correlation. In this paper, the polarization behaviour of indoor channels is investigated. A measurement campaign has been conducted at 3.6 GHz for a dual-polarized transmitter and a tri-polarized receiver in a non-Line-of-Sight (NLOS) scenario. The spatial and delay characteristics are extracted using a per-tap beamforming algorithm. Distinct paths are isolated and the polarization of each wave is expressed in terms of its spherical components. The cross-polarization discrimination (XPD) of the wave is investigated as a function of its physical propagation parameters. The XPD of the wave is shown to be sensitive to spatial characteristics, while being insensitive to delay.
%K MIMO
%K polarization
%K XPD
%K channel modeling
%K directions of arrival (DoA)
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Wireless Communications
%B IEEE Transactions on Wireless Communications
%! IEEE Trans. Wirel. Commun.
%V 9
%N 1
%P 21-25
%D 2010
%@ 1536-1276 (ISSN)
%@ 1558-2248 (e-ISSN)
%* peer-reviewed
%D 2010
%U Handle: http://hdl.handle.net/2078.1/34249
%R 10.1109/TWC.2010.01.081144
%0 Journal Article
%9 Article de recherche
%A Chalise, Batu K.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T A Multiuser MIMO Transmit Beamformer Based on the Statistics of the Signal-to-Leakage Ratio
%X A multiuser multiple-input multiple-output (MIMO) downlink communication system is analyzed in a Rayleigh fading environment. The approximate closed-form expressions for the probability density function (PDF) of the signal-to-leakage ratio (SLR), its average, and the outage probability have been derived in terms of the transmit beamformer weight vector. With the help of some conservative derivations, it has been shown that the transmit beamformer which maximizes the average SLR also minimizes the outage probability of the SLR. Computer simulations are carried out to compare the theoretical and simulation results for the channels whose spatial correlations are modeled with different methods. Copyright (C) 2009 B. K. Chalise and L. Vandendorpe.
%K ICTEAM:COMM
%G Anglais
%J Eurasip Journal On Wireless Communications And Networking
%B Eurasip Journal On Wireless Communications And Networking
%! EURASIP J. Wirel. Commun. Netw.
%D 2009
%@ 1687-1472 (ISSN)
%* peer-reviewed
%D 2009
%U Handle: http://hdl.handle.net/2078.1/35255
%R 10.1155/2009/679430
%0 Journal Article
%9 Éditorial
%A Oestges, Claude
%A Jensen, Michael
%A Kyritsi, Persefoni
%A Shafi, Mansoor
%A Takada, Jun-ichi
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Advances in Propagation Modeling for Wireless Systems
%K ICTEAM:COMM
%G Anglais
%J Eurasip Journal On Wireless Communications And Networking
%B Eurasip Journal On Wireless Communications And Networking
%! EURASIP J. Wirel. Commun. Netw.
%D 2009
%@ 1687-1499 (ISSN)
%* peer-reviewed
%D 2009
%U Handle: http://hdl.handle.net/2078.1/35460
%R 10.1155/2009/415736
%0 Journal Article
%9 Article de recherche
%A Devillers, Bertrand
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Bit Rate Comparison of Adaptive OFDM and Cyclic Prefixed Single-Carrier with DFE
%X This letter considers two variants of a cyclic prefixed block transmission: (i) orthogonal frequency division multiplexing (OFDM), (ii) cyclic prefixed single-carrier (CPSC) transmission with decision feedback equalization (DFE). We aim at comparing these two schemes in terms of achievable bit rate with adaptive bit loading. It is analytically demonstrated that, for all signal to noise ratio values, OFDM achieves a bit rate greater than or equal to that of DFE-CPSC, independently of whether uniform or optimal power allocation is considered.
%K Cyclic prefixed single-carrier
%K multicarrier
%K OFDM
%K ICTEAM:COMM
%G Anglais
%J IEEE Communications Letters
%B IEEE Communications Letters
%! IEEE Commun. Lett.
%V 13
%N 11
%P 838-840
%D 2009
%@ 1089-7798 (ISSN)
%@ 1558-2558 (e-ISSN)
%* peer-reviewed
%D 2009
%U Handle: http://hdl.handle.net/2078.1/35168
%R 10.1109/LCOMM.2009.091008
%0 Journal Article
%9 Article de recherche
%A Brah, Félix
%A Louveaux, Jérôme
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T CDIT-Based Constrained Resource Allocation for Mobile WiMAX Systems
%X Adaptive resource allocation has been shown to provide substantial performance gain in OFDMA-based wireless systems, such as WiMAX, when full channel state information (CSI) is available at the transmitter. However, in some fading environments ( e. g., fast fading), there may not be a feedback link sufficiently fast to convey the CSI to the transmitter. In this paper, we consider resource allocation strategies for downlink multiuser mobile WiMAX systems, where the transmitter has only the channel distribution information (CDI), but no knowledge of the instantaneous channel realization. We address the problem of subchannel assignment and power allocation, to maximize the ergodic weighted-sum rate under long-term fairness, minimum data rate requirement and power budget constraints. This problem is formulated as a nonlinear stochastic constrained optimization problem. We provide an analytical solution based on the Lagrange dual decomposition framework. The proposed method has a complexity of O( KM) for K users and M subchannels. Simulation results are provided to compare the performance of this method with other allocation schemes and to illustrate the tradeoff between maximized weighted-sum rate and the constraints. Copyright (c) 2009 Felix Brah et al.
%K ICTEAM:COMM
%G Anglais
%J Eurasip Journal On Wireless Communications And Networking
%B Eurasip Journal On Wireless Communications And Networking
%! EURASIP J. Wirel. Commun. Netw.
%D 2009
%@ 1687-1472 (ISSN)
%* peer-reviewed
%D 2009
%U Handle: http://hdl.handle.net/2078.1/35795
%R 10.1155/2009/425367
%0 Journal Article
%9 Article de recherche
%A Zaidi, Abdellatif
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Coding Schemes for Relay-Assisted Information Embedding
%X Cooperative information embedding deals with the problem of embedding unperceived information into some cover signal by different users or partners, cooperatively. It models applications in which embedded signals, or watermarks, transmitted over wireless networks need to be reinforced in order to withstand channel impairments. In cooperative information embedding, each embedder that can reinforce the embedded signal may or may not know the original cover signal. In this paper, we concentrate on the two user cases: 1) an initial embedder and 2) an assisting embedder or helper collaborate to embed some watermark into given digital media content which is transmitted over a wireless network. One important application is that of infrastructure-aided information embedding, a case in which the network provider plays the role of a helper and contributes to securing the distribution of the media, not only by blocking unauthorized signals but also by reinforcing the watermarks in legitimate signals. We investigate the two scenarios in which the helper does or does not know the cover signal. For each scenario, we derive lower and upper bounds on channel capacity. Furthermore, we also design implementable coding schemes and derive the embedding rates practically allowed by these schemes, for both scenarios. Among others, the performance characterization shows that for cooperative information embedding to be effective, careful code design is required at the initial embedder and the helper. The careful design concerns the joint conception of the embedded codes and the exploitation of the knowledge of the cover signal, if any.
%K Dirty paper coding (DPC)
%K information embedding (IE)
%K noncausal channel state information
%K relay channel
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Information Forensics and Security
%B IEEE Transactions on Information Forensics and Security
%! IEEE Trans. Inf. Forensic Secur.
%V 4
%N 1
%P 70-85
%D 2009
%@ 1556-6013 (ISSN)
%@ 1556-6021 (e-ISSN)
%* peer-reviewed
%D 2009
%U Handle: http://hdl.handle.net/2078.1/35778
%R 10.1109/TIFS.2008.2009588
%0 Journal Article
%9 Article de recherche
%A Fresia, Maria
%A Vandendorpe, Luc
%A Poor, H. V.
%+ Université catholique de Louvain (UCL)
%T Distributed Source Coding Using Raptor Codes for Hidden Markov Sources
%X In this correspondence, the problem of distributed source coding (DSC) of binary sources with side information at the decoder is addressed. A scheme is proposed based on raptor codes which are a new class of rateless codes. The decoding scheme is adapted to this problem by implementing a message passing strategy between the constituent decoders of raptor codes at each decoding iteration. The case in which the sources are modeled as independent and identically distributed (i.i.d) processes as well as the more general case in which the sources are modeled as hidden Markov processes (HMPs) are considered. The proposed approach achieves better performance than those achieved by the solutions based on turbo codes, and by the solutions based on regular low density parity check (LDPC) codes when i.i.d. sources are considered. On the other hand, when modeling sources as HMPs, an additional module to exploit the underlying Markovian nature is necessary to achieve good performance.
%K Distributed source coding
%K Markov model
%K raptor codes
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%! IEEE Trans. Signal Process.
%V 57
%N 7
%P 2868-2875
%D 2009
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2009
%U Handle: http://hdl.handle.net/2078.1/35518
%R 10.1109/TSP.2009.2018603
%0 Journal Article
%9 Article de recherche
%A Zaidi, Abdellatif
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Lower Bounds on the Capacity of the Relay Channel with States at the Source
%X We consider a state-dependent three-terminal full-duplex relay channel with the channel states noncausally available at only the source, that is, neither at the relay nor at the destination. This model has application to cooperation over certain wireless channels with asymmetric cognition capabilities and cognitive interference relay channels. We establish lower bounds on the channel capacity for both discrete memoryless (DM) and Gaussian cases. For the DM case, the coding scheme for the lower bound uses techniques of rate-splitting at the source, decode-and-forward (DF) relaying, and a Gel'fand-Pinsker-like binning scheme. In this coding scheme, the relay decodes only partially the information sent by the source. Due to the rate-splitting, this lower bound is better than the one obtained by assuming that the relay decodes all the information from the source, that is, full-DF. For the Gaussian case, we consider channel models in which each of the relay node and the destination node experiences on its link an additive Gaussian outside interference. We first focus on the case in which the links to the relay and to the destination are corrupted by the same interference; and then we focus on the case of independent interferences. We also discuss a model with correlated interferences. For each of the first two models, we establish a lower bound on the channel capacity. The coding schemes for the lower bounds use techniques of dirty paper coding or carbon copying onto dirty paper, interference reduction at the source and decode-and-forward relaying. The results reveal that, by opposition to carbon copying onto dirty paper and its root Costa's initial dirty paper coding (DPC), it may be beneficial in our setup that the informed source uses a part of its power to partially cancel the effect of the interference so that the uninformed relay benefits from this cancellation, and so the source benefits in turn. Copyright (c) 2009 A. Zaidi and L. Vandendorpe.
%K ICTEAM:COMM
%G Anglais
%J Eurasip Journal On Wireless Communications And Networking
%B Eurasip Journal On Wireless Communications And Networking
%! EURASIP J. Wirel. Commun. Netw.
%D 2009
%@ 1687-1472 (ISSN)
%* peer-reviewed
%D 2009
%U Handle: http://hdl.handle.net/2078.1/35172
%R 10.1155/2009/634296
%0 Journal Article
%9 Article de recherche
%A Chalise, Batu K.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T MIMO Relay Design for Multipoint-to-Multipoint Communications With Imperfect Channel State Information
%X The problem of designing multiple-input-multiple-output (MIMO) relay for multipoint to multipoint communication in wireless networks has been dealt with by considering the fact that only the imperfect channel state information (CSI) is available at the MIMO relay. In particular, assuming that the second-order terms of the uncertainties of the source-relay and relay-destination channels are negligible, we design an amplify-and-forward (AF) MIMO relay that provides robustness against channel uncertainties. In our proposed robust method, the objective is to design the MIMO relay in which the worst-case relay transmit power is minimized by keeping the worst-case signal-to-interference-and-noise ratio (SINR) for all destinations above a certain threshold value. This paper shows that the aforementioned problem is nonconvex but it can be relaxed to a convex problem consisting of second-order cone (SOC) and semidefinite cone constraints using the semidefinite relaxation technique. The optimal solution of the relaxed problem is utilized to generate the best approximate solution of the original nonconvex problem using the well-known randomization technique. Computer simulations verify the robustness of the proposed MIMO relay when compared to the nonrobust MIMO relay.
%K Channel state information
%K channel uncertainty and convex optimization
%K Robust MIMO relay
%K Worst-case performance optimization
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%! IEEE Trans. Signal Process.
%V 57
%N 7
%P 2785-2796
%D 2009
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2009
%U Handle: http://hdl.handle.net/2078.1/35517
%R 10.1109/TSP.2009.2018610
%0 Journal Article
%9 Article de recherche
%A Quitin, Francois
%A Oestges, Claude
%A Horlin, Francois
%A De Doncker, Philippe
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Multipolarized MIMO Channel Characteristics: Analytical Study and Experimental Results
%X MIMO technologies enable high communication data rates, but suffer from the large antenna spacing that is required to achieve sufficiently low inter-antenna correlation. Cross-polarized antenna systems resolve this problem by using perpendicular antennas. Correlation is reduced while keeping antennas co-located. Inter-antenna correlation and cross-polar discrimination (XPD) are two fundamental parameters of these polarized antenna systems. This paper proposes an analytical channel model, from which closed-form solutions for the correlation coefficient and the XPD are deduced. The environment is supposed to have a truncated Laplacian power azimuth spectrum that is widely used in standardization bodies. The receiving di- or tri-pole antenna can have random orientation. The correlation and the XPD show to be highly sensitive to receiver orientation, azimuth spread and environment depolarization behavior. Measurements have been conducted at 3.5 GHz to validate the solution obtained. Good agreement is achieved when comparing theoretical curves and experimental results for different receiver orientations, both for the correlation coefficient and the XPD.
%K Correlation coefficient
%K cross-polarized
%K MIMO
%K cross-polar discrimination (XPD)
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%! IEEE Trans. Antennas Propag.
%V 57
%N 9
%P 2739-2745
%D 2009
%@ 0018-926X (ISSN)
%@ 1558-2221 (e-ISSN)
%* peer-reviewed
%D 2009
%U Handle: http://hdl.handle.net/2078.1/35335
%R 10.1109/TAP.2009.2027041
%0 Journal Article
%9 Article de recherche
%A Chalise, Batu K.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Performance Analysis of Linear Receivers in a MIMO Relaying System
%X We investigate the performance of linear receivers in a cooperative system which consists of a source, a decode-and-forward (DF) relay and a destination that are all multi-antenna nodes. The relay uses zero-forcing (ZF) equalization whereas the destination employs maximum ratio combining (MRC) as well as ZF techniques. Considering that perfect channel state information is available at the relay and destination, and the fading is Rayleigh, we derive a closed-form approximate expression for the outage. probability of the post-receiver signal-to-noise ratio (SNR) of each data stream at the destination and analyze the diversity order. The validity of the outage probability expression is confirmed with the numerical results.
%K Linear receivers
%K MIMO relay
%K outage probability
%K ICTEAM:COMM
%G Anglais
%J IEEE Communications Letters
%B IEEE Communications Letters
%! IEEE Commun. Lett.
%V 13
%N 5
%P 330-332
%D 2009
%@ 1089-7798 (ISSN)
%@ 1558-2558 (e-ISSN)
%* peer-reviewed
%D 2009
%U Handle: http://hdl.handle.net/2078.1/35581
%R 10.1109/LCOMM.2009.090185
%0 Journal Article
%9 Article de recherche
%A Bandemer, Bernd
%A Oestges, Claude
%A Czink, Nicolai
%A Paulraj, Arogyaswami
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Physically motivated fast-fading model for indoor peer-to-peer channels
%X To model the fast-fading statistics of the wireless transmission channel in indoor peer-to-peer scenarios, an amplitude distribution composed of three distinct components was investigated. They correspond to line-of-sight, once-reflected and twice-reflected propagation paths. It is shown experimentally that this distribution matches indoor peer-to-peer links better than the available alternatives. Furthermore, an interesting structure in the parameter space of the distribution is pointed out, leading to a simple stochastic parameterisation based on a three-modal normal distribution.
%K ICTEAM:COMM
%G Anglais
%J Electronics Letters
%B Electronics Letters
%! Electron. Lett.
%V 45
%N 10
%P 515-516
%D 2009
%@ 0013-5194 (ISSN)
%@ 1350-911X (e-ISSN)
%* peer-reviewed
%D 2009
%U Handle: http://hdl.handle.net/2078.1/35582
%R 10.1049/el.2009.0711
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Villacieros, Belen Montenegro
%A Vanhoenacker-Janvier, Danielle
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Radio Channel Characterization for Moderate Antenna Heights in Forest Areas
%X This paper describes the results achieved by an experimental campaign whose goal was to characterize the directional propagation channel at 1.9 GHz in forested areas for moderate antenna heights. These experimental results are useful in the context of pedestrian radio-localization systems relying on cellphone signals. Wideband experimental results, which are recorded with transmit-to-receive distances ranging from 40 to 110 m, indicate that the path loss is well modeled by ITU-R Recommendation 833-4. The temporal fading and multipath dispersion are also analyzed. The delay spread, which ranges from 60 to 120 ns, is strongly anticorrelated with the temporal coherence and increases with transmit-to-receive distance. The azimuth spread remains limited, with average values of about 15 degrees.
%K Localization
%K radio propagation
%K Ricean fading
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%! IEEE Trans. Veh. Technol.
%V 58
%N 8
%P 4031-4035
%D 2009
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2009
%U Handle: http://hdl.handle.net/2078.1/35251
%R 10.1109/TVT.2009.2024947
%0 Journal Article
%9 Article de recherche
%A Jaspar, Xavier
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - SST/ICTM - Institute for Information and Communication. Technologies, Electronics and Applied Mathematics
%T Random Bit Flipping and EXIT Charts for Nonuniform Binary Sources and Joint Source-Channel Turbo Systems
%X Joint source-channel turbo techniques have recently been explored a lot in literature as one promising possibility to lower the end-to-end distortion, with fixed length codes, variable length codes, and (quasi) arithmetic codes. Still, many issues remain to be clarified before production use. This short contribution clarifies very concisely several issues that arise with EXIT charts and nonuniformbinary sources (a nonuniformbinary source can be the result of a nonbinary source followed by a binary source code). We propose two histogram-based methods to estimate the charts and discuss their equivalence. The first one is a mathematical generalization of the original EXIT charts to nonuniformbits. The second one uses a randombit flipping to make the bits virtually uniform and has two interesting advantages: (1) it handles straightforwardly outer codes with an entropy varying with the bit position, and (2) it provides a chart for the inner code that is independent of the outer code. Copyright (C) 2009 X. Jaspar and L. Vandendorpe.
%K ICTEAM:COMM
%G Anglais
%J Eurasip Journal on Advances in Signal Processing
%B Eurasip Journal on Advances in Signal Processing
%! EURASIP J. Adv. Signal Process.
%D 2009
%@ 1687-6172 (ISSN)
%@ 1687-6180 (e-ISSN)
%* peer-reviewed
%D 2009
%U Handle: http://hdl.handle.net/2078.1/34294
%R 10.1155/2009/354107
%0 Journal Article
%9 Article de recherche
%A Vandendorpe, Luc
%A Louveaux, Jérôme
%A Oguz, Onur
%A Zaidi, Abdellatif
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Rate-Optimized Power Allocation for DF-Relayed OFDM Transmission under Sum and Individual Power Constraints
%X We consider an OFDM (orthogonal frequency division multiplexing) point-to-point transmission scheme which is enhanced by means of a relay. Symbols sent by the source during a first time slot may be (but are not necessarily) retransmitted by the relay during a second time slot. The relay is assumed to be of the DF (decode-and-forward) type. For each relayed carrier, the destination implements maximum ratio combining. Two protocols are considered. Assuming perfect CSI (channel state information), the paper investigates the power allocation problem so as to maximize the rate offered by the scheme for two types of power constraints. Both cases of sum power constraint and individual power constraints at the source and at the relay are addressed. The theoretical analysis is illustrated through numerical results for the two protocols and both types of constraints. Copyright (C) 2009 Luc Vandendorpe et al.
%K ICTEAM:COMM
%G Anglais
%J Eurasip Journal On Wireless Communications And Networking
%B Eurasip Journal On Wireless Communications And Networking
%! EURASIP J. Wirel. Commun. Netw.
%D 2009
%@ 1687-1472 (ISSN)
%* peer-reviewed
%D 2009
%U Handle: http://hdl.handle.net/2078.1/35366
%R 10.1155/2009/814278
%0 Journal Article
%9 Article de recherche
%A Quitin, Francois
%A Oestges, Claude
%A Horlin, François
%A De Doncker, Philippe
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Small-scale variations of cross-polar discrimination in Ricean fading channels
%X Cross-polarised antenna systems are an attractive way to reduce equipment size while maintaining low inter-antenna correlation. The cross-polar discrimination (XPD) is an important parameter of cross-polarised systems. Starting from the definition of Ricean fading channels, it is shown that the small-scale variations of the XPD have a doubly non-central F-distribution. The simulated XPD distribution obtained as a function of the Ricean parameters is successfully compared with measurement results for validation.
%K ICTEAM:COMM
%G Anglais
%J Electronics Letters
%B Electronics Letters
%! Electron. Lett.
%V 45
%N 4
%P 213-214
%D 2009
%@ 0013-5194 (ISSN)
%@ 1350-911X (e-ISSN)
%* peer-reviewed
%D 2009
%U Handle: http://hdl.handle.net/2078.1/35780
%R 10.1049/el:20092524
%0 Journal Article
%9 Article de recherche
%A Benedetto, Francesco
%A Giunta, Gaetano
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T A Blind Equalization Algorithm Based on Minimization of Normalized Variance for DS/CDMA Communications
%X This paper proposes a blind equalizer that pursues the maximization of a novel objective function. It consists of the ratio between the square of the mean signal power and the variance of the signal power. In this paper, important prepositions are first mathematically stated. The devised equalizer is asymptotically equivalent to the well-known constant-modulus algorithm (CMA) and the Kurtosis maximization algorithm (KMA) because they pursue the same "Ricianity" criterion already employed in the "Rayleigh-ness" test for spread-spectrum code acquisition. The performance of the addressed equalizers is then investigated by focusing on direct-sequence code-division multiple-access (DS/CDMA) communication environments in a downlink scenario. In particular, we have evidenced the effectiveness of the presented equalizer in the numerical examples in terms of robustness against the effect of interference, as well as in terms of convergence rate, in spite of a small amount of extra processing.
%K Blind equalization
%K constant-modulus algorithm (CMA)
%K direct-sequence code-division multiple-access (DS/CDMA) communications
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%! IEEE Trans. Veh. Technol.
%V 57
%N 6
%P 3453-3461
%D 2008
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2008
%U Handle: http://hdl.handle.net/2078.1/36238
%R 10.1109/TVT.2008.918693
%0 Journal Article
%9 Article de recherche
%A Devillers, Bertrand
%A Louveaux, Jérôme
%A Vandendorpe, Luc
%+ CTTC, Barcelona, Spain - Access technologies
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T About the Diversity in Cyclic Prefixed Single-Carrier Systems
%X This paper analyzes to what extent the multipath diversity is extracted by a cyclic prefixed single-carrier (CPSC) transmission. The state-of-the-art is currently pessimistic on that issue, and has to be moderated: if it is true that the asymptotical, i.e. at infinite signal to noise ratio (SNR), diversity order achieved by CPSC is equal to one, we prove that the block size has an influence on the performance at moderate SNR. In particular, for reasonably large values of the block size, we show that the multipath diversity can be extracted by CPSC for the range of bit error rate values typically used in practice. The influence of suboptimal linear receivers on the diversity extraction is also investigated.
%K Mutli-carrier
%K OFDM
%K Single-carrier
%K Cyclic prefix
%K Diversity analysis
%K 2556
%K ICTEAM:COMM
%G Anglais
%J Physical Communications
%B Physical Communications
%V 1
%N 4
%P 266-276
%D 2008
%@ 0277-9374 (ISSN)
%* peer-reviewed
%D 2008
%U Handle: http://hdl.handle.net/2078.1/74605
%R 10.1016/j.phycom.2008.12.001
%0 Journal Article
%9 Article de recherche
%A Renaudin, Olivier
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Analysis of inter-tap correlation for measured mobile radio channels at 1.9 GHz
%X Tapped-delay line representations are analysed by presenting an empirical model relating the inter-tap correlation to the tap powers obtained from pedestrian radio channel impulse responses measured at 1.9 GHz. The impact of the filtering bandwidth on the parameters of this model is also investigated.
%K ICTEAM:COMM
%G Anglais
%J Electronics Letters
%B Electronics Letters
%! Electron. Lett.
%V 44
%N 16
%P 945-947
%D 2008
%@ 0013-5194 (ISSN)
%@ 1350-911X (e-ISSN)
%* peer-reviewed
%D 2008
%U Handle: http://hdl.handle.net/2078.1/36418
%R 10.1049/el:20081156
%0 Journal Article
%9 Article de recherche
%A Sartenaer, T.
%A Louveaux, Jérôme
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Balanced capacity of wireline multiple access channels with individual power constraints
%X This paper applies the concept of balanced capacity, a fair trade-off between individual and global performance, to the uplink of a Gaussian frequency-selective multiuser channel with K users, where K can be much larger than 2. Individual power constraints are applied to each transmitter, which makes the computation of the balanced capacity very complex. The concept of 'equivalent channel' is used to derive an explicit expression of the optimal power allocation, that remains compatible with the individual power constraints. The computation of the balanced capacity is then formulated as a set of 2K nonlinear equations. An iterative algorithm providing the exact solution is firstly introduced. A suboptimal solution, based on the Iterative Multiuser Water-Filling (IMWF) algorithm, is then proposed and shown to be very close to the optimal solution: The idea of this alternative method, called 'balanced water-filling', is to modify the power allocation obtained with the IMWF algorithm in order to get balanced data rates. Results are provided for a wireline access network with 20 users.
%K Multiuser Capacity
%K Multiple-access Channel
%K Multiuser Water-filling
%K Balanced Capacity
%K Wireline Channel
%K Powerline Communications
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%! IEEE Trans. Commun.
%V 56
%N 6
%P 925-936
%D 2008
%@ 0090-6778 (ISSN)
%@ 1558-0857 (e-ISSN)
%* peer-reviewed
%D 2008
%U Handle: http://hdl.handle.net/2078.1/59213
%R 10.1109/TCOMM.2008.060331
%0 Journal Article
%9 Article de recherche
%A Devillers, Bertrand
%A Louveaux, Jérôme
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Bit and power allocation for goodput optimization in coded parallel subchannels with ARQ
%X This paper addresses the problem of adaptively allocating the bits and the power among a set of parallel subchannels. A frame-oriented transmission with convolutional coding, hard Viterbi decoding, and automatic repeat request (ARQ) retransmission protocol is considered. The objective is to maximize the number of information bits delivered without error to the user by unit of time, or goodput. This criterion is a tradeoff between the bit rate and bit error probability criteria. First, a mathematical expression for the goodput of the system is presented. Then, using that expression, different bit and power allocation strategies are derived and compared. It turns out that having an equal bit error rate (BER) on each subchannel is near-optimal in terms of goodput. Finally, we prove that the waterfilling solution with adequate signal to noise ratio (SNR) gap value (or equivalently adequate target BER value) is near-optimal. We analytically show how this SNR gap value depends on the convolutional code used, the frame length, the type of ARQ protocol used, the available transmit power, and the subchannel gains.
%K Bit Allocation
%K Goodput
%K Multiple-input Multiple-output (mimo)
%K Orthogonal Frequency-division Multiplexing (ofdm)
%K Power Allocation
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%! IEEE Trans. Signal Process.
%V 56
%N 8
%P 3652-3661
%D 2008
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2008
%U Handle: http://hdl.handle.net/2078.1/59189
%R 10.1109/TSP.2008.925929
%0 Journal Article
%9 Article de recherche
%A Herzet, Cedric
%A Ramon, Valery
%A Renaux, Alexandre
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Cramer-Rao bound characterization of the EM-algorithm mean speed of convergence
%X This paper deals with the mean speed of convergence of the expectation-maximization (EM) algorithm. We show that the asymptotic behavior (in terms of the number of observations) of the EM algorithm can be characterized as a function of the Cramer-Rao bounds (CRBs) associated to the so-called incomplete and complete data sets defined within the EM-algorithm framework. We particularize our result to the case of a complete data set defined as the concatenation of the observation vector and a vector of nuisance parameters, independent of the parameter of interest. In this particular case, we show that the CRB associated to the complete data set is nothing but the well-known modified CRB. Finally, we show by simulation that the proposed expression enables to properly characterize the EM-algorithm mean speed of convergence from the CRB behavior when the size of the observation set is large enough.
%K convergence of numerical methods
%K iterative methods
%K maximum-likelihood estimation
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%! IEEE Trans. Signal Process.
%V 56
%N 6
%P 2218-2228
%D 2008
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2008
%U Handle: http://hdl.handle.net/2078.1/36571
%R 10.1109/TSP.2008.917024
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Clerckx, Bruno
%A Guillaud, Maxime
%A Debbah, Merouane
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Dual-Polarized Wireless Communications: From Propagation Models to System Performance Evaluation
%X In this paper, we address the potential benefits of dual-polarized arrays in multi-antenna wireless systems. After an extensive literature overview of experimental data, we present a new and simple analytical framework to model dual-polarized Rayleigh and Ricean fading channels for arbitrary array sizes. The model relies on a limited number of physical parameters, such as the channel spatial correlations, the channel co-polar and the cross-polar ratios and the antenna cross-polar discrimination. Then, we investigate the multiplexing advantage of dual-polarized transmissions through the evaluation of the ergodic mutual information, for both TITO and MIMO systems.Finally, the performance of two space-time coding schemes (Alamouti O-STBC and uncoded Spatial Multiplexing) is evaluated via a detailed analysis of the pairwise error probability.
%K MIMO
%K polarization
%K propagation
%K mutual information
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Wireless Communications
%B IEEE Transactions on Wireless Communications
%! IEEE Trans. Wirel. Commun.
%V 7
%N 10
%P 4019-4031
%D 2008
%@ 1536-1276 (ISSN)
%@ 1558-2248 (e-ISSN)
%* peer-reviewed
%D 2008
%U Handle: http://hdl.handle.net/2078.1/36867
%R 10.1109/T-WC.2008.070540
%0 Journal Article
%9 Article de recherche
%A Jaspar, Xavier
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Joint Source-Channel Codes based on Irregular Turbo Codes and Variable Length Codes
%X Variable length codes (VLCs), used in data compression, are very sensitive to error propagation in the presence of noisy channels. To address this problem, several joint source-channel turbo techniques have been proposed in the literature. In this paper, we focus on pairs of source/VLC of low redundancy, i.e., when there is a good match between the source statistics and the length distribution of the VLC. It is a case not considered. extensively in the literature so far and the classical concatenation of a VLC and a convolutional code is not satisfying. Through EXIT chart and interleaving gain analysis, we show that the introduction of a repetition code between the VLC and the convolutional code considerably improves global performance. In particular, excellent symbol error rates are obtained with reversible VLCs which are used in recent source codecs.
%K Variable length code
%K irregular turbo code
%K interleaving gain
%K joint source channel
%K EXIT chart
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%! IEEE Trans. Commun.
%V 56
%N 11
%P 1824-1835
%D 2008
%@ 0090-6778 (ISSN)
%@ 1558-0857 (e-ISSN)
%* peer-reviewed
%D 2008
%U Handle: http://hdl.handle.net/2078.1/36239
%R 10.1109/TCOMM.2008.060590
%0 Journal Article
%9 Article de recherche
%A Herzet, Cedric
%A Wymeersch, Henk
%A Simoens, Frederik
%A Moeneclaey, Marc
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T MAP-based code-aided hypothesis testing
%X This contribution deals with code-aided hypothesis testing for wireless digital receivers. We provide a theoretical justification for a hypothesis testing algorithm that was previously introduced in [1] based on ad-hoc arguments. Contrary to conventional hypothesis testing methods, the algorithm from [1] exploits the code structure within the received signal and does not require any pilot symbols. By doing so, it allows to improve the bandwidth-efficiency of the transmission. The present contribution shows that, under mild conditions, the performance of the algorithm from [1] coincides with the performance of the optimal Maximum A Posteriori (MAP) hypotesis test. Computer simulations support this result.
%K MAP estimation
%K synchronization
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Wireless Communications
%B IEEE Transactions on Wireless Communications
%! IEEE Trans. Wirel. Commun.
%V 7
%N 8
%P 2856-2860
%D 2008
%@ 1536-1276 (ISSN)
%@ 1558-2248 (e-ISSN)
%* peer-reviewed
%D 2008
%U Handle: http://hdl.handle.net/2078.1/36361
%R 10.1109/TWC.2008.060995
%0 Journal Article
%9 Éditorial
%A Sari, Hikmet
%A Svensson, Arne
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Multicarrier systems
%K ICTEAM:COMM
%G Anglais
%J Eurasip Journal On Wireless Communications And Networking
%B Eurasip Journal On Wireless Communications And Networking
%! EURASIP J. Wirel. Commun. Netw.
%D 2008
%@ 1687-1472 (ISSN)
%* peer-reviewed
%D 2008
%U Handle: http://hdl.handle.net/2078.1/36739
%R 10.1155/2008/598270
%0 Journal Article
%9 Article de recherche
%A Chalise, Batu K.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Outage probability analysis of a MIMO relay channel with orthogonal space-time block codes
%X We investigate the performance of a cooperative multiple-input multiple-output (MIMO) relay channel in which the source and relay use the same orthogonal space-time block code (OSTBC) for transmission whereas the relay and destination use maximum-ratio-combining (MRC) for reception. Considering that perfect channel state information is available at the relay and destination, we derive a closed-form expression for the outage probability of the destination signal-to-noise ratio (SNR) in terms of the confluent hypergeometric function of two variables in a Rayleigh flat-fading environment. The validity of the closed-form expression is confirmed with the numerical results.
%K MIMO relay
%K outage probability
%K space-time block codes
%K ICTEAM:COMM
%G Anglais
%J IEEE Communications Letters
%B IEEE Communications Letters
%! IEEE Commun. Lett.
%V 12
%N 4
%P 280-282
%D 2008
%@ 1089-7798 (ISSN)
%@ 1558-2558 (e-ISSN)
%* peer-reviewed
%D 2008
%U Handle: http://hdl.handle.net/2078.1/36467
%R 10.1109/LCOMM.2008.072142
%0 Journal Article
%9 Article de recherche
%A Clerckx, Bruno
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Space-time code design for correlated ricean MIMO channels at finite SNR
%X Space-time code (STC) designs commonly rely on the assumptions of independent and identically distributed (i.i.d.) Rayleigh channels (being either slow or fast fading) and high signal-to-noise ratio (SNR). However, it has been shown that poor scattering conditions can have detrimental effects on the performance of STCs and that the behavior of codes at high SNR is radically different from the finite SNR behavior. This calls for new design criteria that correctly predict the behavior of codes in correlated channels at finite SNR. In this paper, we investigate how spatially and temporally correlated Ricean fading affects the performance of STCs at finite SNR. We derive a code design criterion leading to robust STCs in a wide variety of propagation conditions and do not require any channel knowledge at the transmitter. Codes satisfying this criterion are shown to perform sensibly better in correlated channels than codes designed only for i.i.d. slow or fast Rayleigh-fading channels. Examples of space-time trellis codes and algebraic codes are proposed in order to illustrate the developed criterion.
%K correlated channels
%K finite SNR
%K multiple-input multiple-output (MIMO)
%K space-time coding
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%! IEEE Trans. Signal Process.
%V 56
%N 9
%P 4365-4376
%D 2008
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2008
%U Handle: http://hdl.handle.net/2078.1/36410
%R 10.1109/TSP.2008.921811
%0 Journal Article
%A Ramon, Valery
%A Herzet, Cedric
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T A semi-analytical method for predicting the performance and convergence behavior of a multiuser turbo-equalizer/demapper
%X This paper proposes a simple semi-analytical method with reduced simulation time for predicting at any iteration the performance of a turbo-equalization/demapping scheme using the Wang and Poor soft-in/soft-out (SISO) minimum mean-square error (MMSE)/interference cancellation (IC) equalizer and a SISO decoder. The proposed method may be applied to multilevel/phase data modulations as well as multiuser context. This paper shows that the equalizer behavior may be very reliably predicted totally by calculations (no simulations are needed) whereas that of the decoder still requires simulations. A comparison between the proposed prediction method and plain simulations of the overall turbo equalization scheme demonstrates that our method accurately determines the system performance at any iteration. Static channels, long frames, and perfect channel knowledge are assumed throughout the paper.
%K code-division multiple access (CDMA)
%K minimum mean-square error (MMSE) filtering
%K multiuser detection
%K performance analysis
%K soft interference cancellation
%K turbo processing
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%! IEEE Trans. Signal Process.
%V 55
%N 3
%P 1104-1117
%D 2007
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2007
%U Handle: http://hdl.handle.net/2078.1/37736
%R 10.1109/TSP.2006.887137
%0 Journal Article
%A Herzet, Cedric
%A Ramon, Valery
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T A theoretical framework for iterative synchronization based on the sum-product and the expectation-maximization algorithms
%X This paper deals with maximum-likelihood (ML) estimation of synchronization parameters for coded transmission systems. In particular, we present a unified framework based on both the sum-product (SP) algorithm and the expectation-maximization (EM) algorithm for the design of iterative synchronizers. The proposed approach is shown to encompass some known iterative synchronizers. In particular, we revisit a previously proposed framework based on the EM algorithm only by means of our "SP-EM" approach. The performance of the proposed synchronization method is assessed in terms of mean-square error and bit-error rate by simulation results. In particular, we consider the joint synchronization of the timing epoch and the carrier phase offset in the case of convolutionally coded and turbo-coded transmissions.
%K iterative methods
%K maximum-likelihood estimation
%K message passing
%K synchronization
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%! IEEE Trans. Signal Process.
%V 55
%N 5
%P 1644-1658
%D 2007
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2007
%U Handle: http://hdl.handle.net/2078.1/37642
%R 10.1109/TSP.2006.890828
%0 Journal Article
%A Giunta, Gaetano
%A Vandendorpe, Luc
%A Benedetto, F.
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T All-pass prefiltering in pre-post-rake schemes for spread-spectrum communications
%X Pre-Post-Rake is a known technique in spread-spectrum communications that uses one rake filter at the transmitter side (to partially precompensate for the wireless channel dispersion) and one rake filter at the receiver side (matched to the entire transmitter plus channel chain). A novel scheme based on transmitter all-pass filtering has been employed by the authors to enhance the performance in the downlink of direct sequence code division multiple access (DS/CDMA) system. In this correspondence, we explain by theoretical analysis why the structure performs well. In particular, we show that the interference can be reduced by all-pass prefiltering. In fact, it basically acts as a (phase-only) preequalizer of the multipath channel that combats intersymbol interference. On the other hand, it better preserves the orthogonality between near orthogonal pseudorandom codes in multiuser synchronous DS/CDMA environments. The performance is analyzed for wireless multipath channels, simulated by realistic models, to evidence its gain (in terms of dispersion index) compared to conventional pre-post-rake.
%K all-pass digital filters
%K rake receivers
%K signal processing algorithms for mobile communications
%K spread-spectrum communications
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%! IEEE Trans. Signal Process.
%V 55
%N 8
%P 4330-4334
%D 2007
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2007
%U Handle: http://hdl.handle.net/2078.1/37486
%R 10.1109/TSP.2007.896089
%0 Journal Article
%A Herzet, Cedric
%A Noels, Nele
%A Lottici, Vincenzo
%A Wymeersch, Henk
%A Luise, Marco
%A Moeneclaey, Marc
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Code-aided turbo synchronization
%X The introduction of turbo and low-density parity-check (LDPC) codes with iterative decoding that almost attain Shannon capacity challenges the synchronization subsystems of a data modem. Fast and accurate signal synchronization has to be performed at a much lower value of signal-to-noise ratio (SNR) than in previous less efficiently coded systems. The solution to this issue is developing specific synchronization techniques that take advantage of the presence of the channel code and of the iterative nature of decoding: the so-called turbo-synchronization algorithms. The aim of this paper within this special issue devoted to the turbo principle is twofold: on the one hand, it shows how the many turbo-synchronization algorithms that have already appeared in the literature can be cast into a simple and rigorous theoretical framework. On the other hand, it shows the application of such techniques in a few simple cases, and evaluates improvement that can be obtained from them, especially in the low-SNR regime.
%K iterative methods
%K maximum likelihood estimation
%K synchronization
%K ICTEAM:COMM
%G Anglais
%J Institute of Electrical and Electronics Engineers. Proceedings
%B Institute of Electrical and Electronics Engineers. Proceedings
%! Proc. IEEE
%V 95
%N 6
%P 1255-1271
%D 2007
%@ 0018-9219 (ISSN)
%@ 1558-2256 (e-ISSN)
%* peer-reviewed
%D 2007
%U Handle: http://hdl.handle.net/2078.1/37408
%R 10.1109/JPROC.2007.896518
%0 Journal Article
%A Wautelet, Xavier
%A Herzet, Cedric
%A Dejonghe, Antoine
%A Louveaux, Jérôme
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Comparison of EM-based algorithms for MIMO channel estimation
%X Iterative channel estimation can improve the channel-state information (CSI) with respect to noniterative estimation. New iterative channel estimators based on the expectation-maximization (EM) algorithm are proposed in this paper. A first estimator, called the unbiased EM (UEM), is designed to unbias the EM estimates. A second estimator is then put forward, which is based on the expectation-conditional-maximization (ECM) algorithm, and its complexity is lower than that of the EM. An unbiased ECM (UECM) estimator is also proposed. Although the unbiasedness of the UEM and UECM estimators is not rigorously proved, the use of these names is explained in the paper. The new estimators are compared with well-known ones, such as the EM, the decision-directed (DD), and the data-aided (DA) estimators. Simulations are reported for a turbo receiver operating over frequency-selective multiple-input multiple-output channels. It is shown that the UEM channel estimator outperforms the EM, and that the ECM-based estimators are very close to the EM-based ones.
%K Channel Estimation
%K Expectation-maximization (em) Algorithm
%K Iterative Estimation
%K Multiple-input Multiple-output (mimo) Systems
%K Turbo Detection
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%! IEEE Trans. Commun.
%V 55
%N 1
%P 216-226
%D 2007
%@ 0090-6778 (ISSN)
%@ 1558-0857 (e-ISSN)
%* peer-reviewed
%D 2007
%U Handle: http://hdl.handle.net/2078.1/59712
%R 10.1109/TCOMM.2006.887507
%0 Journal Article
%A Clerckx, Bruno
%A Oestges, Claude
%A Vandendorpe, Luc
%A Vanhoenacker-Janvier, Danielle
%A Paulraj, Arogyaswami J.
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Design and performance of space-time codes for spatially correlated MIMO channels
%X Space-time code (STC) designs classically rely on the assumption of independent and identically distributed (i.i.d.) Rayleigh channels. However, poor scattering conditions may have detrimental effects on the performance of STCs. In this letter, we derive code-design criteria leading to robust STCs in a large variety of slow-fading propagation conditions. No channel knowledge is assumed at the transmitter. Codes satisfying these criteria are shown to perform much better on real-world channels than codes designed only for i.i.d. channels. As examples, the robustness of various spatial multiplexing schemes, linear dispersion codes, and space-time trellis codes is discussed based on those criteria.
%K correlated channels
%K multiple-input multiple-output (MIMO)
%K space-time coding
%K spatial multiplexing (SM)
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%! IEEE Trans. Commun.
%V 55
%N 1
%P 64-68
%D 2007
%@ 0090-6778 (ISSN)
%@ 1558-0857 (e-ISSN)
%* peer-reviewed
%D 2007
%U Handle: http://hdl.handle.net/2078.1/37789
%R 10.1109/TCOMM.2006.885063
%0 Journal Article
%9 Article de recherche
%A Clerckx, Bruno
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Finite-SNR performance analysis of space-time coding in correlated Ricean MIMO channels
%X The performance analysis and the subsequent design of space-time codes (STC) in multiantenna channels commonly assume an infinite signal-to-noise ratio (SNR). This assumption has been shown to be justified in uncorrelated Rayleigh-fading channels. By contrast, this correspondence investigates STC in all SNR regimes and in the broad class of space-time correlated Ricean fading multiple-input-multiple-output (MIMO) channels. For rank-deficient codes, it is proven analytically that the error probability is significantly affected by spatial correlations and coherent components, irrespective of the SNR range and the temporal correlation. For full-rank codes, the performance and the code design are shown to be affected by spatial correlations and/or coherent paths only at finite SNR in slow fading channels, whereas in time-varying channels, they are affected in all SNR regimes. Hence, there is no guarantee that STC designed for independent and indentically distributed (i.i.d.) Rayleigh-fading channels perform adequately in space-time correlated Rayleigh/Ricean channels. Simulation examples confirm the conclusions drawn from the analytical derivations. They further illustrate that the use of a high SNR assumption does not allow to accurately estimate the behavior of STC in practical scenarios and should, thus, be used with care.
%K correlated channels
%K fading channels
%K finite signal-to-noise ratio (SNR)
%K multiple-input-multiple-output (MIMO)
%K pairwise error probability
%K space-time coding (STC)
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Information Theory
%B IEEE Transactions on Information Theory
%! IEEE Trans. Inf. Theory
%V 53
%N 12
%P 4761-4777
%D 2007
%@ 0018-9448 (ISSN)
%@ 1557-9654 (e-ISSN)
%* peer-reviewed
%D 2007
%U Handle: http://hdl.handle.net/2078.1/36923
%R 10.1109/TIT.2007.909075
%0 Journal Article
%9 Article de recherche
%A Clerckx, Bruno
%A Craeye, Christophe
%A Vanhoenacker-Janvier, Danielle
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Impact of antenna coupling on 2 x 2 MIMO communications
%X The impact of mutual coupling induced by two closely spaced minimum scattering antennas at the subscriber unit on 2 x 2 multiple-input multiple-output channels and communicaions is investigated. Both (de)correlation effects and variations of antenna gain resulting from coupling mechanisms are considered. Relationships between coupling and correlations/channel Frobenius norm are discussed, pointing out the role of the interelement spacing, the array orientation, and the richness of scattering. The analysis also yields useful insight into the influence of mutual coupling on capacity and system performance.
%K antenna array
%K multiple-input multiple-output (MIMO) systems
%K mutual coupling
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%! IEEE Trans. Veh. Technol.
%V 56
%N 3
%P 1009-1018
%D 2007
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2007
%U Handle: http://hdl.handle.net/2078.1/37561
%R 10.1109/TVT.2007.895545
%0 Journal Article
%A Jaspar, Xavier
%A Guillemot, Christine
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Joint source-channel turbo techniques for discrete-valued sources: From theory to practice
%X The principles which have been prevailing so far for designing communication systems rely on Shannon's source and channel coding separation theorem. This theorem states that source and channel optimum performance bounds can be approached as close as desired by designing independently the source and channel coding strategies. However, this theorem holds only under. asymptotic conditions, where both codes are allowed infinite length and complexity. If the design of the system is constrained in terms of delay and complexity, if the sources are not stationary, or if the channels are nonergodic, separate design and optimization of the source and channel coders can be largely suboptimal. For practical systems, joint source-channel (de)coding may reduce the end-to-end distortion. It is one of the aspects covered by the term cross-layer design, meaning a rethinking of the layer separation principle. This article focuses on recent developments of joint source-channel turbo coding and decoding techniques, which are described in the framework of normal factor graphs. The scope is restricted to lossless compression and discrete-valued sources. The presented techniques can be applied to the quantized values of a lossy source codec but the quantizer itself and its impact are not considered.
%K channel code
%K cross-layer design
%K iterative decoding
%K joint source-channel code
%K source code
%K turbo principle
%K ICTEAM:COMM
%G Anglais
%J Institute of Electrical and Electronics Engineers. Proceedings
%B Institute of Electrical and Electronics Engineers. Proceedings
%! Proc. IEEE
%V 95
%N 6
%P 1345-1361
%D 2007
%@ 0018-9219 (ISSN)
%@ 1558-2256 (e-ISSN)
%* peer-reviewed
%D 2007
%U Handle: http://hdl.handle.net/2078.1/37409
%R 10.1109/JPROC.2007.896491
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Clerckx, Bruno
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Modeling outdoor macrocellular clusters based on 1.9-GHz experimental data
%X This paper presents a stochastic geometry-based model of the multiple-input-multiple-output channel, as seen by the user terminal based on the extraction of cluster parameters from wideband data measured at 1.9 GHz in short-range outdoor macrocellular environments. Clusters are first identified through data visual inspection. Then, a statistical characterization is carried out based on a delay-oriented classification of the clusters. Extraction results show that at each location, six to eight clusters are present, with average cluster delay and azimuth root mean square spreads of about 10-15 ns and 10 degrees-20 degrees, respectively. A cluster-oriented geometry-based model is then developed and validated with measurement results, including spatial correlations for broadside and inline receive antenna configurations.
%K clustering
%K multiple-input multiple-output (MIMO) channels
%K radio propagation
%K suburban areas
%K urban areas
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%! IEEE Trans. Veh. Technol.
%V 56
%N 5
%P 2821-2830
%D 2007
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2007
%U Handle: http://hdl.handle.net/2078.1/37313
%R 10.1109/TVT.2007.900391
%0 Journal Article
%A Herzet, Cedric
%A Wymeersch, Henk
%A Moeneclaey, Marc
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T On maximum-likelihood timing synchronization
%X In this letter, we address the issue of symbol timing recovery for a coded burst transmission system. As direct maximum-likelihood (ML) estimation is intractable, we resort to the expectation-maximization (EM) algorithm in order to derive a receiver that iterates between data detection and synchronization. Conventional data-aided (DA) and decision-directed (DD) synchronizers can be interpreted as special cases of the proposed algorithm. The EM-based technique takes into account code properties and is especially well suited to scenarios where conventional schemes fail to provide the detector with a reliable timing estimate. The performance of the proposed algorithm is compared with conventional techniques through computer simulations, both in terms of mean-square estimation error (MSEE) and bit error rate (BER).
%K iterative methods
%K maximum-likelihood estimation
%K synchronization
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%! IEEE Trans. Commun.
%V 55
%N 6
%P 1116-1119
%D 2007
%@ 0090-6778 (ISSN)
%@ 1558-0857 (e-ISSN)
%* peer-reviewed
%D 2007
%U Handle: http://hdl.handle.net/2078.1/37513
%R 10.1109/TCOMM.2007.898863
%0 Journal Article
%9 Article de recherche
%A Van Roy, Stéphane
%A Oestges, Claude
%A Horlin, Francois
%A De Doncker, Philippe
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T On-body propagation velocity estimation using ultra-wideband frequency-domain spatial correlation analyses
%X On-body communications around the human torso are considered, using ultra-wideband transmissions. The velocity of the diffracted wave propagating around the body is extracted from frequency-domain spatial correlation analyses.
%K ICTEAM:COMM
%G Anglais
%J Electronics Letters
%B Electronics Letters
%! Electron. Lett.
%V 43
%N 25
%P 1405-1406
%D 2007
%@ 0013-5194 (ISSN)
%@ 1350-911X (e-ISSN)
%* peer-reviewed
%D 2007
%U Handle: http://hdl.handle.net/2078.1/36889
%R 10.1049/el:20073090
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Propagation channel, capacity and error probability for dual-polarized wireless transmissions
%X Use of dual-polarized arrays in multiple-input multiple-output (MIMO) systems is addressed in this paper. A new and simple analytical model of dual-polarized Rayleigh and Ricean fading channels is taken, which relies on a limited number of physical parameters, such as the spatial correlations, the co-polar gain imbalance and the cross-polar discrimination. Then, the multiplexing advantage of dual-polarized transmissions is investigated through the evaluation of the ergodic mutual information. Finally, the performance of two space-time coding schemes (Alamouti O-STBC and un-coded Spatial Multiplexing) is evaluated via a detailed analysis of the pair-wise error probability (PEP).
%K ICTEAM:COMM
%G Anglais
%J Indian Journal of Radio & Space Physics
%B Indian Journal of Radio & Space Physics
%! Indian J. Radio Space Phys. (India)
%V 36
%N 5
%P 411-417
%D 2007
%@ 0367-8393 (ISSN)
%* peer-reviewed
%D 2007
%U Handle: http://hdl.handle.net/2078.1/66175
%Z Oestges, C.; Microwave Lab., Univ. Catholique de Louvain,Louvain-la-Neuve, Belgium
%0 Journal Article
%9 Article de recherche
%A Vanhoenacker-Janvier, Danielle
%A Oestges, Claude
%A Martelucci, Antonio
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Scintillation and depolarisation models for satellite communications in the 20-50 GHz band
%X This paper presents improved methods for the prediction of cumulative distribution of scintillation variance, using radiosonde data. This method has the advantage of being usable all around the world and its accuracy is improved with respect to classical methods based only on ground measured data. The second part presents a two-layer depolarisation model separating rain and ice effects for better scalability.
%K ICTEAM:COMM
%G Anglais
%J Indian Journal of Radio & Space Physics
%B Indian Journal of Radio & Space Physics
%! Indian J. Radio Space Phys. (India)
%V 36
%N 5
%P 369-374
%D 2007
%@ 0367-8393 (ISSN)
%* peer-reviewed
%D 2007
%U Handle: http://hdl.handle.net/2078.1/66176
%Z Vanhoenacker-Janvier, D.; Oestges, C.; Microwave Lab., Univ. Catholiquede Louvain, Louvain-la-Neuve, Belgium
%0 Journal Article
%A Almers, Peter
%A Bonek, Ernst
%A Burr, Alister G.
%A Czink, Nicolai
%A Debbah, Merouane
%A Degli-Esposti, Vittorio
%A Hofstetter, Helmut
%A Kyosti, Pekka
%A Laurenson, Dave
%A Matz, Gerald
%A Molisch, Andreas
%A Oestges, Claude
%A Oezcelik, Huseyin
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Survey of channel and radio propagation models for wireless MIMO systems
%X This paper provides an overview of the state-of- the-art radio propagation and channel models for wireless multiple-input multiple-output (MIMO) systems. We distinguish between physical models and analytical models and discuss popular examples from both model types. Physical models focus on the double-directional propagation mechanisms between the location of transmitter and receiver without taking the antenna configuration into account. Analytical models capture physical wave propagation and antenna configuration simultaneously by describing the impulse response (equivalently, the transfer function) between the antenna arrays at both link ends. We also review some MIMO models that are included in current standardization activities for the purpose of reproducible and comparable MIMO system evaluations. Finally, we describe a couple of key features of channels and radio propagation which are not sufficiently included in current MIMO models. Copyright c 2007 P. Almers et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
%K ICTEAM:COMM
%G Anglais
%J Eurasip Journal On Wireless Communications And Networking
%B Eurasip Journal On Wireless Communications And Networking
%! EURASIP J. Wirel. Commun. Netw.
%D 2007
%@ 1687-1499 (ISSN)
%* peer-reviewed
%D 2007
%U Handle: http://hdl.handle.net/2078.1/37460
%R 10.1155/2007/19070
%0 Journal Article
%9 Article de recherche
%A Louveaux, Jérôme
%A van der Veen, Alle-Jan
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Adaptive DSL crosstalk precancellation design using low-rate feedback from end users
%X The performance of extensions of digital subscriber line to higher data rates (VDSL) is limited by the effects of crosstalk among the wires in a bundle. For the downstream, a precoder can compensate for this. Without knowledge of the crosstalk channel matrix, the problem is to compute a suitable precoder based on limited feedback from the receivers. In this letter, an adaptive precoder design algorithm is derived. The algorithm works on a per-tone basis and assumes that each receiver sends back the sign of the symbol error to the transmitter. The algorithm computes the precoder iteratively using this information, without the need to estimate the crosstalk channel as an intermediate step. The asymptotic and acquisition performance is verified by simulations.
%K adaptive algorithm
%K channel estimation
%K crosstalk
%K precoder design
%K vectored DSL
%G Anglais
%J IEEE Signal Processing Letters
%B IEEE Signal Processing Letters
%! IEEE Signal Process. Lett.
%V 13
%N 11
%P 665-668
%D 2006
%@ 1070-9908 (ISSN)
%@ 1558-2361 (e-ISSN)
%* peer-reviewed
%D 2006
%U Handle: http://hdl.handle.net/2078.1/38122
%R 10.1109/LSP.2006.879476
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Vanhoenacker-Janvier, Danielle
%A Clerckx, Bruno
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Channel characterization of indoor wireless personal area networks
%X The wireless channel for nomadic diversity-based wireless networks operating at 1.9 GHz is characterized. Using a 1 x 2 wideband measurement chain, four typical indoor office and industrial environments have been investigated: a corridor, an office room, a laboratory room and a large industrial hall. The measurement equipment is constituted by an 80-MHz transmitter. At the receiver, two omnidirectional antennas are connected to a wideband channel sounder through a switch, in order to measure an estimate of the instantaneous vector channel. Special attention is given to the experimental procedure itself so as to take into account the specificity of nomadic systems (a opposed to usual mobile systems). The measurement analysis reveals that the shadowing, Rician K-factor and delay-spread are lognormally distributed. A path-loss model is derived, and cross-correlations between K-factor, delay-spread and shadowing are analyzed. The channel correlations at the user terminal or at the access point are also derived, and related to the individual channel characteristics.
%K diversity
%K indoor radio communications
%K radio propagation
%K Rician channels
%K wireless LAN
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%! IEEE Trans. Antennas Propag.
%V 54
%N 11
%P 3143-3150
%D 2006
%@ 0018-926X (ISSN)
%@ 1558-2221 (e-ISSN)
%* peer-reviewed
%D 2006
%U Handle: http://hdl.handle.net/2078.1/38141
%R 10.1109/TAP.2006.883962
%0 Journal Article
%9 Article de recherche
%A Louveaux, Jérôme
%A van der Veen, A.
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Error Sign Feedback as an Alternative to Pilots for the Tracking of FEXT Transfer Functions in Downstream VDSL
%X With increasing bandwidths and decreasing loop lengths, crosstalk becomes the main impairment in VDSL systems. For downstream communication, crosstalk precompensation techniques have been designed to cope with this issue by using the collocation of the transmitters. These techniques naturally need an accurate estimation of the crosstalk channel impulse responses. We investigate the issue of tracking these channels. Due to the lack of coordination between the receivers, and because the amplitude levels of the remaining interference from crosstalk after precompensation are very low, blind estimation schemes are inefficient in this case. So some part of the upstream or downstream bit rate needs to be used to help the estimation. In this paper, we design a new algorithm to try to limit the bandwidth used for the estimation purpose by exploiting the collocation at the transmitter side. The principle is to use feedback from the receiver to the transmitter i! nstead of using pilots in the downstream signal. It is justified by computing the Cramer-Rao lower bound on the estimation error variance and showing that, for the levels of power in consideration, and for a given bit rate used to help the estimation, this bound is effectively lower for the proposed scheme. A simple algorithm based on the maximum likelihood is proposed. Its performance is analyzed in detail and is compared to a classical scheme using pilot symbols. Finally, an improved but more complex version is proposed to approach the performance bound.
%K ICTEAM:COMM
%G Anglais
%J EURASIP Journal on Applied Signal Processing (Special Issue on Advanced Signal Processing Techniques for DSL)
%B EURASIP Journal on Applied Signal Processing (Special Issue on Advanced Signal Processing Techniques for DSL)
%V 2006
%N 2006
%P Article ID 94105, 14 p.
%D 2006
%@ 1110-8657 (ISSN)
%@ 1687-0433 (e-ISSN)
%* peer-reviewed
%D 2006
%U Handle: http://hdl.handle.net/2078.1/90129
%R 10.1155/ASP/2006/94105
%0 Journal Article
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Mutual information of non-Kronecker structured dual-polarized 2 x 2 channels
%X This paper investigates the mutual information of several 2 x 2 systems using orthogonal polarizations. Analytical approximations of the mutual information in equi-power allocation scenarios are derived and compared in both Rayleigh and Ricean fading conditions.
%K capacity
%K multiple-input multiple-output (MIMO)
%K polarization
%K Ricean fading
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%! IEEE Trans. Veh. Technol.
%V 55
%N 1
%P 410-413
%D 2006
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2006
%U Handle: http://hdl.handle.net/2078.1/38652
%R 10.1109/TVT.2005.858182
%0 Journal Article
%A Sartenaer, T.
%A Vandendorpe, Luc
%A Louveaux, Jérôme
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Balanced capacity of wireline multiuser channels
%X This paper analyzes the multiuser capacity of Gaussian frequency-selective wireline multiaccess channels. Both the uplink (multiple-access channel) and downlink (broadcast channel) capacity regions are considered. The concept of balanced capacity is introduced to characterize the multiuser channel performance. Algorithms for the computation of the balanced multiuser capacity (and the associated power allocations) are proposed for an arbitrary number of users. The optimal power allocation in a K-user memoryless Gaussian channel is analyzed in detail, and an extension to intersymbol interference channels is given with various kinds of power constraints. Results are provided for a wireline access network with 20 users.
%K Broadcast Channel (bc)
%K Multiple-access (ma) Channel
%K Multiuser Capacity
%K Multiuser Waterfilling
%K Wireline Channel
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%! IEEE Trans. Commun.
%V 53
%N 12
%P 2029-2042
%D 2005
%@ 0090-6778 (ISSN)
%@ 1558-0857 (e-ISSN)
%* peer-reviewed
%D 2005
%U Handle: http://hdl.handle.net/2078.1/60114
%R 10.1109/TCOMM.2005.860106
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Kim, Arnold D.
%A Papanicolaou, George
%A Paulraj, Arogyaswami
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Characterization of space-time focusing in time-reversed random fields
%X This paper proposes various, metrics to characterize space-time focusing resulting from application of time reversal, techniques in richly scattering media. The concept and goals of time reversal are presented. Pertinent metrics describing both the time and space focusing effects are outlined. Two examples based on a model of discrete and continuous scattering media are used to illustrate how the proposed metrics vary as a function of various system and channel parameters, such as the bandwidth, delay and angle spreads, number of antennas, etc.
%K random media
%K space-time focusing
%K time reversal
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Antennas and Propagation
%B IEEE Transactions on Antennas and Propagation
%! IEEE Trans. Antennas Propag.
%V 53
%N 1
%P 283-293
%D 2005
%@ 0018-926X (ISSN)
%@ 1558-2221 (e-ISSN)
%* peer-reviewed
%D 2005
%U Handle: http://hdl.handle.net/2078.1/39624
%R 10.1109/TAP.2004.836399
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Clerckx, Bruno
%A Vanhoenacker-Janvier, Danielle
%A Paulraj, Arogyaswami
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Impact of fading correlations on MIMO communication systems in geometry-based statistical channel models
%X This paper highlights the impact of channel correlations on the capacity and performance of MIMO communications, with a focus on the so-called diagonal correlations. Based on this analysis, the limitations of simplified mathematical representations, such as the Kronecker or the diagonal-decorrelation models, are pointed out. Finally, the correlation properties of popular geometry-based statistical models are studied in order to analyze whether the correlation structure of these models can be adequately represented by simplified mathematical models, as well as to quantify the errors introduced by these simplifications. With respect to channel correlations, neither the Kronecker nor the diagonal-decorrelation assumptions are good representations of the correlation structure of the investigated geometry-based statistical models. When comparing capacity and symbol error probability results, it is found that the diagonal-decorrelation model may yield significant errors on both considered metrics. The Kronecker model generally yields errors less than one order of magnitude on the symbol error rate, but relative errors on ergodic or outage capacity may be more significant.
%K communication system performance
%K correlation
%K MIMO systems
%K Rayleigh channels
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Wireless Communications
%B IEEE Transactions on Wireless Communications
%! IEEE Trans. Wirel. Commun.
%V 4
%N 3
%P 1112-1120
%D 2005
%@ 1536-1276 (ISSN)
%@ 1558-2248 (e-ISSN)
%* peer-reviewed
%D 2005
%U Handle: http://hdl.handle.net/2078.1/39391
%R 10.1109/TWC.2005.847000
%0 Journal Article
%9 Article de recherche
%A Giunta, G
%A Neri, A
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL)
%T Initial code synchronization of W-CDMA mobile systems exploiting local phase coherence and Pisarenko estimation
%X Noncoherent techniques can be adopted for pseudonoise code synchronization in the presence of random phase. Differentially coherent methods conversely operate with linear phase shifts, such as when a systematic frequency error occurs. This letter presents a method exploiting local phase Coherence (inspired by the Pisarenko estimation), allowing global frequency estimation in the presence of random phase noise. Its accuracy is numerically compared with noncoherent and differential techniques for the initial stage of wideband code-division multiple-access code synchronization.
%K code synchronization
%K hypothesis testing
%K spread-spectrum communications
%K wideband code-division multiple access (W-CDMA)
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%! IEEE Trans. Commun.
%V 53
%N 1
%P 48-52
%D 2005
%@ 0090-6778 (ISSN)
%@ 1558-0857 (e-ISSN)
%* peer-reviewed
%D 2005
%U Handle: http://hdl.handle.net/2078.1/39566
%R 10.1109/TCOMM.2004.840671
%0 Journal Article
%A Labeau, F.
%A Chiang, JC
%A Kieffer, M
%A Duhamel, P.
%A Vandendorpe, Luc
%A Macq, Benoît
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Oversampled filter banks as error correcting codes: Theory and impulse noise correction
%X Oversampled filter banks (OFBs) provide an overcomplete representation of their input signal. This paper describes how OFBs can be considered as error-correcting codes acting on real or complex sequences, very much like classical binary convolutional codes act on binary sequences. The structured redundancy introduced by OFBs in subband signals can be used to increase robustness to noise. In this paper, we define the notions of code subspace, syndrome, and parity-check polynomial matrix for OFBs. Furthermore, we derive generic expressions for projection-based decoding, suitable for the case when a simple second-order model completely characterizes the noise incurred by subband signals. We also develop a nonlinear hypotheses-test based decoding algorithm for the case when the noise in subbands is constituted by a Gaussian background noise and impulsive errors (a model that adequately describes the action of both quantization noise and transmission errors). Simulation results show that the algorithm effectively removes the effect of impulsive errors occurring with a probability of 10(-3).
%K Error Correction Coding
%K Impulse Noise
%K Multirate Filter Banks
%K Oversampling
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%! IEEE Trans. Signal Process.
%V 53
%N 12
%P 4619-4630
%D 2005
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2005
%U Handle: http://hdl.handle.net/2078.1/60807
%R 10.1109/TSP.2005.859314
%0 Journal Article
%A Oezcelik, Huseyin
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Some remarkable properties of diagonally correlated MIMO channels
%X This paper investigates so-called diagonally correlated multiple input-multiple output (MIMO) channels, which provide higher ergodic capacity than independent and identically distributed (i.i.d.) fading channels. The presented analysis details physical scenarios leading to such channels, some properties of the channel matrix, and an analytical expression for its ergodic capacity.
%K capacity
%K correlation
%K multiple-input multiple-output (MIMO)
%K polarization
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%! IEEE Trans. Veh. Technol.
%V 54
%N 6
%P 2143-2145
%D 2005
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2005
%U Handle: http://hdl.handle.net/2078.1/38714
%R 10.1109/TVT.2005.858193
%0 Journal Article
%9 Éditorial
%A Vandendorpe, Luc
%A Haimovich, AM
%A Pyndiah, R
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Special issue on turbo processing
%G Anglais
%J Eurasip Journal on Applied Signal Processing
%B Eurasip Journal on Applied Signal Processing
%! EURASIP J Appl. Signal Process.
%V 2005
%N 6
%P 759-761
%D 2005
%@ 1110-8657 (ISSN)
%* peer-reviewed
%D 2005
%U Handle: http://hdl.handle.net/2078.1/39211
%R 10.1155/ASP.2005.759
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Paulraj, Arogyaswami
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Beneficial impact of channel correlations on MIMO capacity
%X The potential beneficial impact of channel correlations on the capacity of MIMO systems is investigated. In contrast to most previous work, the present analysis is based on a comprehensive model of the channel correlation structure. It is therefore illustrated that fading cross-correlations may increase the ergodic capacity, sometimes even beyond the supposedly ideal case of independent channels. Starting from considerations on an analytical upper bound of the capacity, the study is then supported by simulation results of the actual ergodic capacity in arbitrary MIMO channels using a simple geometry-based stochastic model.
%K ICTEAM:COMM
%G Anglais
%J Electronics Letters
%B Electronics Letters
%! Electron. Lett.
%V 40
%N 10
%P 606-608
%D 2004
%@ 0013-5194 (ISSN)
%@ 1350-911X (e-ISSN)
%* peer-reviewed
%D 2004
%U Handle: http://hdl.handle.net/2078.1/40157
%R 10.1049/el:20040417
%0 Journal Article
%A Dejonghe, Antoine
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL)
%T Bit-interleaved turbo equalization over static frequency-selective channels: Constellation mapping impact
%X The purpose is to assess the performance of bit-interleaved turbo equalization (TE) over static frequency-selective channels. The asymptotic performance is therefore first pointed out, emphasizing the fundamental role played by the constellation mapping. This specific feature is then further analyzed using the extrinsic information-transfer chart technique, leading to an efficient optimization tool. This finally enables showing that bit-interleaved TE can outperform its symbol-interleaved counterpart.
%K Bit-interleaved Coded Modulation (bicm)
%K Extrinsic Information-transfer (exit) Charts
%K Minimum Mean-square Error (mmse)-based Equalization
%K Trellis-coded Modulation (tcm)
%K Turbo Demodulation (td)
%K Turbo Equalization (te)
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%! IEEE Trans. Commun.
%V 52
%N 12
%P 2061-2065
%D 2004
%@ 0090-6778 (ISSN)
%@ 1558-0857 (e-ISSN)
%* peer-reviewed
%D 2004
%U Handle: http://hdl.handle.net/2078.1/61092
%R 10.1109/TCOMM.2004.838708
%0 Journal Article
%9 Article de recherche
%A Desset, C
%A Macq, Benoît
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Computing the word-, symbol-, and bit-error rates for block error-correcting codes.
%X In order to select error-correcting codes for various applications, their performances have to be determined. However, when targeting error-rate computations for block error-correcting codes, many required results are missing in the coding literature. Even in the simple case of binary codes and bounded-distance decoding,, classical texts do not provide a bit-error rate (BER) expression taking into account both decoding errors and failures. In the case of nonbinary codes used to protect binary symbols, such as Reed-Solomon codes in many applications, there is no available result making realistic channel assumptions in order to derive BERs. Finally, for the more complex case of complete decoding, only some bounds are available, such as the union one. This paper presents new approximations of error rates for block error-correcting codes as a function of the channel BER (crossover probability). We extend an existing approximation in order to consider not only bounded-distance decoding, but also complete "nearest-neighbor" decoding. We also develop approximations able to deal with nonbinary codes. Combined with state-of-the-art approximations, these new results enable the computation of bit-, symbol-, and word-error rates in various decoding situations. They can consider separately errors related to erroneously decoded words and decoding failures, and they provide accurate estimates of error rates. As they do not require detailed information about the structure of codes, they are general enough to be used in simple comparisons between different codes, avoiding the need for simulations.
%K bit-error rate (BER)
%K block error-correcting codes
%K complete decoding
%K error-rates computation
%K nonbinary codes
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%! IEEE Trans. Commun.
%V 52
%N 6
%P 910-921
%D 2004
%@ 0090-6778 (ISSN)
%@ 1558-0857 (e-ISSN)
%* peer-reviewed
%D 2004
%U Handle: http://hdl.handle.net/2078.1/40131
%R 10.1109/TCOMM.2004.829509
%0 Journal Article
%9 Article de recherche
%A Sartenaer, T.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL)
%T Linear and DF joint detectors for DS-CDMA communications using periodic long codes
%X Detection structures for a direct sequence (DS) code division multiple access (CDMA) multiuser uplink using codes with a period of several symbols, called long codes, are investigated. In a first part, we propose a multirate description of the uplink. Based on this formalism, we revisit the linear and decision feedback minimum mean square error (MMSE) detectors. In order to identify the best attainable performance, we focus on the infinite size versions. In a second part, reduced complexity, solutions are put forward and discussed. Finally, the performance of the proposed detectors is investigated and compared with that of the classical rake receiver and the single-bit horizon detectors. The relevance of the different solutions is discussed in the light of the channel length.
%K DFE
%K DS-CDMA
%K joint detection
%K long codes
%K MMSE
%K multipath channels
%K rake receivers
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%! IEEE Trans. Signal Process.
%V 52
%N 7
%P 2080-2091
%D 2004
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2004
%U Handle: http://hdl.handle.net/2078.1/40130
%R 10.1109/TSP.2004.828914
%0 Journal Article
%9 Lettre à l'éditeur
%A Wautelet, X.
%A Dejonghe, Antoine
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T MMSE-based fractional turbo receiver for space-time BICM over frequency-selective MIMO fading channels
%X Space-time bit-interleaved coded multilevel modulation over frequency-selective multiple-input multiple-output (MIMO) fading channels is considered. The receiver is turbo based. A soft-input soft-output (SISO) space-time fractionally spaced equalizer is designed for the minimum mean square error (MMSE) criterion. Simulation results show the ability of the receiver to account for intersymbol interference, co-antenna interference, and its capability to exploit transmit, multipath, and receive diversity. These results are also compared to a bit-error-rate lower bound.
%K BICM
%K frequency-selective channels
%K MIMO
%K MMSE
%K space-time coding
%K turbo equalization
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%! IEEE Trans. Signal Process.
%V 52
%N 6
%P 1804-1809
%D 2004
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2004
%U Handle: http://hdl.handle.net/2078.1/40179
%R 10.1109/TSP.2004.827198
%0 Journal Article
%9 Article de recherche
%A Horlin, F.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL)
%T MU-MIMO channel adapted precoding for MAI/ISI-free uplink burst transmission
%X This paper considers the uplink of a multiuser direct-sequence code-division multiple-access communication system based on burst transmission over frequency-selective channels. A new precoding method is presented that is able to take benefit from the space diversity introduced at the mobile transmitters and at the common receiver. User-specific spreading codes are designed so that filters matched to the total impulse responses can remove completely the interference and maximize the signal-and-interference-plus-noise ratios. It is analytically proved that an infinite number of solutions is available to orthogonalize the system. Three particular solutions are considered. A progressive solution is firstly proposed to provide orthogonality in a simple way. Then a near-optimum solution is proposed to orthogonalize the system while attempting to reduce the total transmitted power. The minimization of the total transmitted power is a complex problem of nonlinear optimization that can only be solved using an iterative algorithm. The third solution proposed is based on an iterative algorithm. Those three solutions are analyzed in term of their different performance for a varying number of transmit and receive antennas. A comparison is also provided with a system using a conventional set of binary codes and linear or decision-feedback minimum mean-square error joint detection. It is shown that the near-optimum and iterative solutions are the only ones that are able to fully benefit from the space diversity.
%K adaptive codes
%K code-division multiple access (CDMA)
%K multiuser communication
%K multiuser multiple-input multiple-output (MU-MIMO)
%K precoding
%K space diversity
%K time-dispersive channels
%K uplink
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%! IEEE Trans. Commun.
%V 52
%N 1
%P 100-109
%D 2004
%@ 0090-6778 (ISSN)
%@ 1558-0857 (e-ISSN)
%* peer-reviewed
%D 2004
%U Handle: http://hdl.handle.net/2078.1/40390
%R 10.1109/TCOMM.2003.822177
%0 Journal Article
%9 Article de recherche
%A Czyz, J.
%A Kittler, J
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL)
%T Multiple classifier combination for face-based identity verification
%X When combining outputs from multiple classifiers, many combination rules are available. Although easy to implement, fixed combination rules are optimal only in restrictive conditions. We discuss and evaluate their performance when the optimality conditions are not fulfilled. Fixed combination rules are then compared with trainable combination rules on real data in the context of face-based identity verification. The face images are classified by combining the outputs of five different face verification experts. It is demonstrated that a reduction in the error rates of up to 50% over the best single expert is achieved on the XM2VTS database, using either fixed or trainable combination rules. (C) 2004 Pattern Recognition Society. Published by Elsevier Ltd. All rights reserved.
%K face authentication
%K face verification
%K identity verification
%K multiple classifier systems
%K classifier combination
%K a posteriori probability
%K linear discriminant analysis
%G Anglais
%J Pattern Recognition
%B Pattern Recognition
%! Pattern Recognit.
%V 37
%N 7
%P 1459-1469
%D 2004
%@ 0031-3203 (ISSN)
%@ 1873-5142 (e-ISSN)
%* peer-reviewed
%D 2004
%U Handle: http://hdl.handle.net/2078.1/40153
%R 10.1016/j.patcog.2004.01.008
%0 Journal Article
%9 Article de recherche
%A Clerckx, Bruno
%A Vandendorpe, Luc
%A Vanhoenacker-Janvier, Danielle
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Optimization of nonlinear signal constellations for real-world MIMO channels
%X The performance of spatial multiplexing (SM) multiple-input multiple-output (MIMO) communication systems is highly dependent on the richness of scattering, the presence of dominant components, and the interelement spacings. In. this paper, a new interpretation of the impact of transmit correlation on the performance of SM is given based on a so-called "symbol-related array factor." Nonlinear signal constellations for SM over real-world fading channels are then designed by minimizing an estimate of the average symbol error rate under an average transmit power constraint. The new transmission scheme exploits the spectral. efficiency advantage of SM and the robustness of eigen-beamforming. Through simulations, it is shown to be more robust against fading correlations and high Ricean K-factors than SM using the classical phase shift keying (PSK) and quadrature amplitude modulation (QAM) constellations. The symbol error rate performance of this scheme is not affected by a change in the propagation environment or the interelement distance. furthermore, if the scheme is used on the uplink, no explicit rate-consuming feedback link from the base station to the mobile station is required.
%K beamforming
%K correlated channels
%K multiple-input multiple-output (MIMO)
%K space-time coding
%K spatial multiplexing
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%! IEEE Trans. Signal Process.
%V 52
%N 4
%P 894-902
%D 2004
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2004
%U Handle: http://hdl.handle.net/2078.1/40296
%R 10.1109/TSP.2004.823486
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Paulraj, Arogyaswami
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Propagation into buildings for broad-band wireless access
%X This paper describes measurements of the outdoor-to-indoor channel conducted in the Seattle, WA, and San Francisco Bay, CA, areas at 2.5 GHz. With broad-band wireless access in mind, an empirical model similar to the COST 231 model is built from the measured data. The impacts of wall material, angle of incidence, and receive height are noted and introduced in the modeling approach.
%K attenuation
%K indoor propagation
%K wireless systems
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%! IEEE Trans. Veh. Technol.
%V 53
%N 2
%P 521-526
%D 2004
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2004
%U Handle: http://hdl.handle.net/2078.1/40295
%R 10.1109/TVT.2004.823546
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Erceg, Vinko
%A Paulraj, Arogyaswami
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Propagation modeling of MIMO multipolarized fixed wireless channels
%X This paper addresses the extension of a stochastic geometry-based scattering model to multipolarized transmissions. The initial approach is based on a geometrical distribution of obstacles derived from known power-delay profiles. Each scattering process is statistically described by a matrix reflection coefficient corresponding to dual-polarization states. Ultimately, the model allows us to simulate the effects of the range on K-factor, delay-spread, Doppler spectrum, channel correlations and capacity, branch power ratio, and cross-polar discrimination. Simulation results are compared with existing measurements at 2.5 GHz. The proposed model is then used to investigate various dual-polarization 2 x 2 multiple-input-multiple-output (MIMO) schemes such as 0degrees/90degrees or +/-45degrees, as well as to optimize the design of multipolarized MIMO schemes.
%K microwave radio propagation
%K multiple-input-multiple-output (MIMO)
%K polarization
%K wireless local area network (WLAN)
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%! IEEE Trans. Veh. Technol.
%V 53
%N 3
%P 644-654
%D 2004
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2004
%U Handle: http://hdl.handle.net/2078.1/40178
%R 10.1109/TVT.2004.827149
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Paulraj, Arogyaswami
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Range and antenna beamwidth dependencies in multidimensional fixed wireless channels
%X This paper describes a multidimensional model of the fixed wireless propagation channel, which is well suited to system-level simulations. The proposed method yields realistic predictions of various channel characteristic parameters as a function of the range and antenna beamwidths, in agreement with experimentally observed results. The originality of the approach is that the power-delay profile for omnidirectional antennas at the edge of the cell is used to predict the time-varying channel over the whole cell for any antenna beamwidth. The method is based on a set of spatially distributed scatterers, which can be scaled to any range within the cell. The time-varying channel impulse response is then calculated as the combination of all scattered contributions by means of a ray approximation. The multidimensionality of the channel model is explored through predictions of signal statistics, level-crossing rate, delay-spread and angle-spread. In contrast to most existing models, the impact of range and antenna beamwidth is clearly addressed and found to be close to experimentally observed behaviors.
%K broadband communication
%K multipath channels
%K propagation
%K scattering
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Wireless Communications
%B IEEE Transactions on Wireless Communications
%! IEEE Trans. Wirel. Commun.
%V 3
%N 1
%P 128-137
%D 2004
%@ 1536-1276 (ISSN)
%@ 1558-2248 (e-ISSN)
%* peer-reviewed
%D 2004
%U Handle: http://hdl.handle.net/2078.1/40429
%R 10.1109/TWC.2003.821136
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Vanhoenacker-Janvier, Danielle
%A Clerckx, Bruno
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Wide-band SIMO 1 x 2 measurements and characterization of outdoor wireless channels at 1.9 GHz
%X This paper aims at characterizing the spatial wireless channel at 1.9 GHz, based on a 1 x 2 measurement chain. A typical campus/residential area and an industrial area have been investigated. The measurement equipment is constituted by an 80-MHz transmitter at 1.9 GHz, located at the top of a building. At the receiver, two onmidirectional antennas are connected to a wide-band channel sounder through a switch in order to measure an estimate of the instantaneous vector channel. It is found that the Ricean K-factor and the delay spread are lognormally distributed, while the azimuth spread at the receive side follows a Gaussian distribution. The range dependence of various parameters are pointed out and compared with empirical models. The impacts of antenna spacing and array orientation on the channel correlation are highlighted and compared to theoretical simulation results. Finally, the cross-correlation properties between K-factor, delay spread, azimuth spread, and channel correlation are analyzed.
%K multipath channels
%K multiple-input-multiple-output (MIMO) channels
%K radio propagation
%K urban areas
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%! IEEE Trans. Veh. Technol.
%V 53
%N 4
%P 1190-1202
%D 2004
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2004
%U Handle: http://hdl.handle.net/2078.1/40074
%R 10.1109/TVT.2004.830946
%0 Journal Article
%9 Article de recherche
%A Giunta, G
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL)
%T A "Rayleigh-ness" test for DS/SS code acquisition
%X Testing for statistical distribution has received increasing attention in signal processing for communications. Noncoherent receivers, based on correlation magnitude, are employed when the actual carrier phase of the received samples,is unknown. This paper presents a new test, based on high-order statistics, to decide whether a real positive white series is a realization of a Rayleigh-distributed random process. Such a "Rayleigh-ness" test is based on a testing variable that measures the "Ricianity" of the series under investigation. That is, it estimates the possible presence of the mean of the complex Gaussian model generating both Rayleigh and Rice distributions. The asymptotic testing statistics have been derived as explicit functions of the higher order moments of the noise-plus-interference distribution. The performance of the Rayleigh-ness test has been analyzed in comparison with a conventional power detector. The devised test has application to noncoherent initial synchronization of the chip offset (code acquisition) in a symbol-length spreading sequence of direct-sequence code-division multiple-access systems. In such a case, the noise-plus-interference variance under the out-of-sync condition is much larger than the effective variance in the in-sync case. The obtained results evidence the robustness of the Rayleigh-ness test, avoiding the severe performance, degradation in the presence of large Gaussian and non-Gaussian noise, as well as multiuser interference in a downlink scenario.
%K code acquisition
%K code-division multiple access (CDMA)
%K higher order statistics
%K hypothesis testing
%K spread spectrum (SS) communication
%K synchronization
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%! IEEE Trans. Commun.
%V 51
%N 9
%P 1492-1501
%D 2003
%@ 0090-6778 (ISSN)
%@ 1558-0857 (e-ISSN)
%* peer-reviewed
%D 2003
%U Handle: http://hdl.handle.net/2078.1/40777
%R 10.1109/TCOMM.2003.816971
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Erceg, Vinko
%A Paulraj, Arogyaswami
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T A physical scattering model for MIMO macrocellular broadband wireless channels
%X This paper presents a physical scattering model that predicts multiple-input multiple-output (MIMO) channel characteristics conforming well to experimental observations in macrocells. Our approach is to start with a given single-input single output-power-delay profile (defined for specific range, bandwidth and antenna parameters) and fit a scattering model that characterizes. the MIMO. channel. From the derived scattering model and antenna array configurations, the MIMO channel is computed using a ray-based method. Simulations of several MIMO channels are shown to exhibit experimentally observed channel correlations, antenna beamwidth effect, range dependency and frequency selectivity.
%K broadband communication
%K indexing terms multiple-input multiple-output (MIMO) systems
%K multipath channels
%K propagation
%K scattering
%K ICTEAM:COMM
%G Anglais
%J IEEE Journal on Selected Areas in Communications
%B IEEE Journal on Selected Areas in Communications
%! IEEE J. Sel. Areas Commun.
%V 21
%N 5
%P 721-729
%D 2003
%@ 0733-8716 (ISSN)
%@ 1558-0008 (e-ISSN)
%* peer-reviewed
%D 2003
%U Handle: http://hdl.handle.net/2078.1/40972
%R 10.1109/JSAc.2003.810322
%0 Journal Article
%9 Article de recherche
%A Louveaux, Jérôme
%A Cuvelier, L.
%A Vandendorpe, Luc
%A Pollet, T.
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Baud rate timing recovery scheme for filter bank-based multicarrier transmission
%X This paper is devoted to the design and the steady-state performance analysis of a data-aided or decision-directed timing recovery scheme for filter bank-based multicarrier transmission with equalization. The symbol synchronizer is obtained from a Mueller and Muller approach extended to multi-band transmission. A simple synchronizer is first proposed which can be derived from an approximate likelihood function. Then, possible improvements are discussed. Timing jitter variances are computed and discussed for high bit-rate transmission over copper wires.'
%K filter bank
%K Mueller and Mueller
%K multicarrier transmission
%K synchronization
%K timing recovery
%K very high data-rate digital subscriber line (VDSL)
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%! IEEE Trans. Commun.
%V 51
%N 4
%P 652-663
%D 2003
%@ 0090-6778 (ISSN)
%@ 1558-0857 (e-ISSN)
%* peer-reviewed
%D 2003
%U Handle: http://hdl.handle.net/2078.1/41035
%R 10.1109/TCOMM.2003.810816
%0 Journal Article
%9 Article de recherche
%A Ciblat, P.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL)
%T Blind, carrier, frequency offset estimation for noncircular constellation-based transmissions
%X We address the problem of nondata aided frequency offset estimation for noncircular transmissions over frequency-selective channels in a linear precoder-based communications context. Linear precoding is representative of a downlink direct-sequence code division multiple access (DS-CDMA) system or of an orthogonal frequency division multiplexing (OFDM) system. We observe that twice the frequency offset is a cyclic frequency of the received signal. We thus introduce an estimator relying on the maximization of the empirical cyclocorrelations. We analyze its asymptotic behavior and obtain a closed-form expression for the asymptotic covariance. This enables us to design relevant system parameters. Numerical illustrations are provided and confirm our theoretical assertions. Comparisons with existing methods are also, reported.
%K blind estimation
%K carrier frequency offset
%K cyclic frequency
%K DS-CDMA
%K fading channel
%K harmonic retrieval
%K noncircular constellation
%K OFDM
%K synchronization
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%! IEEE Trans. Signal Process.
%V 51
%N 5
%P 1378-1389
%D 2003
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2003
%U Handle: http://hdl.handle.net/2078.1/41081
%R 10.1109/TSP.2003.810287
%0 Journal Article
%A Horlin, F.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL)
%T CA-CDMA: Channel-adapted CDMA ford MAI/ISI-free burst transmission
%X This paper proposes a precoding technique for the complete elimination of both multiple-access interference and intersymbol interference in the uplink of a code-division multiple-access system based on burst transmission, with reduction of the minimum mean-square error joint detector to a simple filter matched to the total impulse responses. If the received power is fixed, this system minimizes the variance of the symbol estimation error. An infinity of solutions exists to orthogonalize the system. Two objectives are added: a possible progression in, the number of users and a minimization of the average emitted power. In an ideal progressive system, users can enter or leave the system easily without recomputing the codes of the other users. The minimization of the emitted power is a complex optimization problem. An approximate solution is proposed. It is shown that the system introduced in this paper outperforms burst systems using a conventional set of codes.
%K Code Design
%K Code-division Multiple Access (cdma)
%K Joint Transmit And Receive Optimization
%K Multiuser Channels
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%! IEEE Trans. Commun.
%V 51
%N 2
%P 275-283
%D 2003
%@ 0090-6778 (ISSN)
%@ 1558-0857 (e-ISSN)
%* peer-reviewed
%D 2003
%U Handle: http://hdl.handle.net/2078.1/61587
%R 10.1109/TCOMM.2003.809255
%0 Journal Article
%9 Article de recherche
%A Louveaux, Jérôme
%A Vandendorpe, Luc
%A Sartenaer, T.
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Cyclic prefixed single carrier and multicarrier transmission: Bit rate comparison
%X We consider cyclic prefixed single carrier and adaptive multicarrier transmission over a frequency selective channel. We compare the achievable bit rate for a target bit error rate. We analytically prove that the bit rate achieved with multicarrier transmission with adaptive modulation is always higher than that obtained with single carrier transmission when a one-tap frequency domain equalizer is used. We also show that the same adaptively loaded multicarrier scheme reaches the performance of single carrier transmission with a block decision-feedback equalizer.
%K cyclic prefix
%K frequency-domain equalization
%K multicarrier
%G Anglais
%J IEEE Communications Letters
%B IEEE Communications Letters
%! IEEE Commun. Lett.
%V 7
%N 4
%P 180-182
%D 2003
%@ 1089-7798 (ISSN)
%@ 1558-2558 (e-ISSN)
%* peer-reviewed
%D 2003
%U Handle: http://hdl.handle.net/2078.1/41082
%R 10.1109/LCOMM.2003.811202
%0 Journal Article
%9 Article de recherche
%A Louveaux, Jérôme
%A Vandendorpe, Luc
%A Sartenaer, T.
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Early-late timing recovery with decision-feedback equalizers
%X In this paper we revisit the early-late timing recovery scheme developed for filter bank based multicarrier transmission. A substantial improvement is proposed for the case where the receiver contains a decision-feedback equalizer. We show how the timing error detector has to be modified to account for the high level of self-noise and how this self-noise can be mitigated thanks to the introduction of a correction term. We investigate the tracking performance of this new synchronizer for high bit rate transmission over copper wires.
%J IEEE Communications Letters
%B IEEE Communications Letters
%! IEEE Commun. Lett. (USA)
%V 7
%N 7
%P 332-334
%D 2003
%@ 1089-7798 (ISSN)
%* peer-reviewed
%D 2003
%U Handle: http://hdl.handle.net/2078.1/66218
%R 10.1109/LCOMM.2003.814713
%Z Louveaux, J.; Vandendorpe, L.; Sartenaer, T.; Commun. & Remote SensingLab., Univ. catholique de Louvain, Louvain-la-Neuve, Belgium
%0 Journal Article
%9 Article de recherche
%A Horlin, F.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL)
%T A comparison between chip fractional and non-fractional sampling for a direct sequence CDMA receiver
%X This paper examines the effects of chip fractional (CF) and chip nonfractional (CNF) sampling on the performance of a CDMA uplink receiver. The impact of the receiver front end filter, which is sampling rate dependent, is investigated. Models for burst and continuous transmissions are introduced. The discrete-time equivalent channels between the various users and the receiver are assumed to be known. First, the mutual information between the emitted sequences of symbols and the received sequence is investigated. It is analytically shown that the receiver systematically loses information in case of CNF sampling. Second, we have demonstrated that the CF receiver always achieves better performance in terms of minimum mean square error (MMSE) for both linear and decision feedback (DF) structures. A closed-form expression of the gain in performance is provided for the two metrics under consideration. The importance of the gain due to CF sampling is also illustrated by means of computations for multipath channels. For a typical system setup, a gain of 0.1 bits per emitted symbol is observed for the mutual information. Considering the geometrical mean of symbol SINRs in case of linear and DF joint detection (JD) for a roll-off factor equal to 0.3, a gain of 0.4 dB arises for the CF linear detector, and a gain of 0.2 dB arises for the CF DF detector.
%K CDMA
%K joint detection
%K multiuser communications
%K sampling rate
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%! IEEE Trans. Signal Process.
%V 50
%N 7
%P 1713-1723
%D 2002
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2002
%U Handle: http://hdl.handle.net/2078.1/41842
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T A stochastic geometrical vector model of macroand megacellular communication channels
%X This paper describes a physically based stochastic approach that allows to predict the narrowband fading statistics for macro- and megacellular networks operating in urban areas. On one hand, macrocellular channels have been mainly covered in the literature by means of empirical models. On the other hand, megacells are typical of upcoming communication systems, such as broadband wireless access and high-altitude platform-based networks. Generally, the path gain of a wireless fading channel can be statistically characterized by a Ricean distribution, which includes Rayleigh fading as a particular case. The key parameter of the distribution is the K-factor K, defined as the ratio of the dominant component to the scatter contribution. In this paper, the K-factor is estimated by means of a physical model, conditionally to a set of geometrical parameters, such as the building height, the street width and the base station-to-terminal distance. These parameters are statistically described by analytical distributions. The model is successfully compared with experimental data at 1.6 GHz and typical applications are presented. Finally, because of its physical background, the model performs very well in analyzing polarization (MIMO) multiplexing schemes.
%K mobile communication
%K polarization
%K radio propagation
%K urban areas
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%! IEEE Trans. Veh. Technol.
%V 51
%N 6
%P 1352-1360
%D 2002
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2002
%U Handle: http://hdl.handle.net/2078.1/41252
%R 10.1109/TVT.2002.802976
%0 Journal Article
%9 Article de recherche
%A Desset, C
%A Macq, Benoît
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Block error-correcting codes for systems with a very high BER: Theoretical analysis and application to the protection of watermarks
%X This paper addresses the problem of error-correction for extremely noisy channels (BER from 0.1 to 0.5), such as those obtained for image or video watermarking. Minimum distance arguments are used to identify a region for which no other code is as efficient as repetition codes, whatever the rate, at least when bounded decoding is considered. However, in order to obtain a reasonable and sufficiently low BER, repetition codes are not very efficient. We present a coding scheme concatenating a repetition code with another one, and design rules in order to select these codes for a given watermarking application are developed. The repetition code lowers the huge channel BER, as no other code can do this part of the job. Then, the second more powerful code working at a lower BER achieves a larger BER reduction. In this paper, this role is devoted to BCH codes, as members of a classical family. Thanks to their moderate decoding complexity, they turn out to be an interesting cost versus performance trade-off, while more efficient coding schemes based on soft decoding are far more complex. However, we also provide an idea of the solutions to consider for watermarking applications with fewer complexity limitations, for which more powerful decoding techniques can be implemented. (C) 2002 Published by Elsevier Science B.V.
%K image watermarking
%K high BER channels
%K minimum distance
%K repetition codes
%K block error-correcting codes
%G Anglais
%J Signal Processing: Image Communication
%B Signal Processing: Image Communication
%! Signal Process.-Image Commun.
%V 17
%N 5
%P 409-421
%D 2002
%@ 0923-5965 (ISSN)
%* peer-reviewed
%D 2002
%U Handle: http://hdl.handle.net/2078.1/41836
%R 10.1016/S0923-5965(02)00010-3
%0 Journal Article
%9 Article de recherche
%A Horlin, F.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL) - Autre
%T Channel adapted precoding for interference-free uplink burst transmission
%X Direct sequence code division multiple access (DS-CDMA) is a multi-user transmission technique. If channel conditions as experienced by the receiver on one side of the link are known at the transmitter on the other side, the transmitter can predistort the signal in order to overcome the effect of the channel at the receiver. Transmitter optimization, in addition to receiver optimization, contributes significantly to efficient interference suppression in multiple-access and multi-path channels. The method presented rely on the knowledge about all user channels at the base station. The case of a single user system has been deeply studied by Scaglione, Giannakis and Barbarossa (see IEEE Transactions on Signal Processing, vol. 47, no.7, p.1988-2006, 1999). Transmitter and receiver filter-bank pairs are designed according to the MMSE criterion under a constraint of intersymbol interference (ISI) suppression. The MMSE criterion is also applied under a transmitted power constraint. The present paper proposes a precoding technique for the complete elimination of both MAI and ISI in the uplink of a CDMA system based on burst transmission, with reduction of the MMSE joint detector to a simple filter matched to the total impulse responses. As degrees of freedom are still left at this stage additional objectives are introduced. It is further requested that the emitted power be minimized. The progressive solution and the close to optimum one introduced by Horlin and Vandendorpe (see Proc. IEEE -TCC'2001, Helsinki, Finland, June 2001) are compared to the optimal solution obtained at the output of an iterative algorithm. A system using a conventional set of binary codes jointly with a linear or DF MMSE joint detector is also envisaged for the comparison.
%J Acta Technica Belgica. Revue H F: Electricite Courants Faibles. Electronique Telecommunications
%B Acta Technica Belgica. Revue H F: Electricite Courants Faibles. Electronique Telecommunications
%! Rev. HF (Belgium)
%N 2
%P 65-67
%D 2002
%@ 0035-3248 (ISSN)
%* peer-reviewed
%D 2002
%U Handle: http://hdl.handle.net/2078.1/66235
%Z Horlin, F.; Vandendorpe, L.; Commun. & Remote Sensing Lab., Univ.Catholique de Louvain, Louvain-la-Neuve, Belgium
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Clerckx, Bruno
%A Raynaud, Lidwine
%A Vanhoenacker-Janvier, Danielle
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Deterministic channel modeling and performance simulation of microcellular wide-band communication systems
%X To evaluate the performance of future microcellular IMT-2000 modems, simple physical models are required, so that a number of system characteristics, such as the signal bandwidth, the antenna beamwidth, or the base station height can be accounted for at a limited computational cost. This paper describes a deterministic three-dimensional electromagnetic model, which allows simulation of the radiowave propagation for microcellular wide-band communication systems in urban areas. The model is based on a UTD ray-tracing tool and makes use of an improved mirror method. Simulated power-delay profiles are plotted against measured power-delay profiles recorded at 1.87 GHz in a street of Louvain-la-Neuve, Belgium, by means of an 80-MHz channel sounder. Despite several discrepancies, a satisfying matching is found considering three orders of reflection and single diffraction. Predictions of rms delay-spread accounting for the sounder limited bandwidth are presented. Finally, simulated and measured channels are also compared through the resulting performance of a typical IMT-2000 service in the presence of multiple access interference.
%K communication system performances
%K ray tracing
%K wide-band radio channel measurements
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%! IEEE Trans. Veh. Technol.
%V 51
%N 6
%P 1422-1430
%D 2002
%@ 0018-9545 (ISSN)
%* peer-reviewed
%D 2002
%U Handle: http://hdl.handle.net/2078.1/41253
%R 10.1109/TVT.2002.804846
%0 Journal Article
%9 Article de recherche
%A Labeau, F.
%A Desset, C
%A Vandendorpe, Luc
%A Macq, Benoît
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Performances of linear tools and models for error detection and concealment in subband image transmission
%X In this paper, we investigate the performances of Gaussian modeling and linear prediction tools for error detection and concealment in the transmission of still images. We consider the transmission of subband encoded images through two types of channels. We model the residual correlation between subband coefficients by considering them as jointly Gaussian variables. The first transmission medium considered is a packet-oriented channel, where some packets are lost during transmission. The problem is to estimate the values of missing coefficients. In this case, particular care must be taken while evaluating correlation matrices from incomplete data. The other system considered is based on a discrete memoryless noisy channel affecting the data being transmitted. The challenge is here first to determine the locations of the errors-which is done through hypotheses tests-and then to replace them by estimates based on their neighbors. The reconstruction via linear prediction is shown to give better results than median filtering based reconstruction. Error detection through this Gaussian model also shows promising results, in particular when channel statistics are taken into account in a joint source-channel decoding framework.
%K error detection and concealment
%K joint source-channel coding
%K residual redundancy
%G Anglais
%J IEEE Transactions on Image Processing
%B IEEE Transactions on Image Processing
%! IEEE Trans. Image Process.
%V 11
%N 5
%P 518-529
%D 2002
%@ 1057-7149 (ISSN)
%@ 1941-0042 (e-ISSN)
%* peer-reviewed
%D 2002
%U Handle: http://hdl.handle.net/2078.1/41905
%R 10.1109/TIP.2002.1006399
%0 Journal Article
%9 Article de recherche
%A Salvekar, AA
%A Louveaux, Jérôme
%A Aldana, C
%A Fang, JL
%A de Carvalho, E
%A Cioffi, JM
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Profile detection in multiuser digital subscriber line systems
%X Multiuser transmission methods for digital subscriber line (DSL) systems have become of interest with the potential for increased data rate and loop reach. These methods often assume that the set of crosstalk interferers, called the crosstalk profile, and their associated channel responses are known. For DSL systems, the interferers are often uncoordinated, so that in a dynamic environment where DSL transmitters can energize and deenergize, the crosstalk profile cannot be transmitted to the user of interest. While the crosstalk channel estimation problem in a dynamic environment can be intractable for general transmission systems, channel and crosstalk analysis can make use of the specific DSL environment. Namely, the physical channels in a DSL system do not change rapidly, and hence estimates of the crosstalk channel can be saved for future reference. For this reason, we introduce the concept of a channel profile. We develop several algorithms to detect the crosstalk profile and investigate the asymptotic behavior of the new algorithms. Simulations show that for typical crosstalk interference scenarios, the observation time to determine the correct crosstalk profile at probability of error less than 10(-3) can be less than 2 ms.
%K crosstalk
%K crosstalk profile
%K digital subscriber line (DSL)
%K multiuser detection (MUD)
%K multiuser transmission (MUT)
%K profile detection
%G Anglais
%J IEEE Journal on Selected Areas in Communications
%B IEEE Journal on Selected Areas in Communications
%! IEEE J. Sel. Areas Commun.
%V 20
%N 5
%P 1116-1125
%D 2002
%@ 0733-8716 (ISSN)
%@ 1558-0008 (e-ISSN)
%* peer-reviewed
%D 2002
%U Handle: http://hdl.handle.net/2078.1/41906
%R 10.1109/JSAC.2002.1007391
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Vanhoenacker-Janvier, Danielle
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T A physical-statistical shadowing correlation model and its application to low-earth-orbit systems
%X A shadowing correlation model is proposed in the context of a physical-statistical approach in the view of satellite diversity in built-up areas, The model relies on a model based on the uniform theory of diffraction, applied in a canonical built-up scenario. The correlation model is described and simulation results are presented and analyzed within a physical point of view, The shadowing correlation model is finally applied to several low-earth-orbit constellations, The impact of geometrical parameters and of the constellation is investigated.
%K communication system performances
%K correlation
%K satellite mobile communications
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%! IEEE Trans. Veh. Technol.
%V 50
%N 2
%P 416-421
%D 2001
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2001
%U Handle: http://hdl.handle.net/2078.1/42734
%R 10.1109/25.923053
%0 Journal Article
%9 Article de recherche
%A Louveaux, Jérôme
%A Vandendorpe, Luc
%A Cuvelier, L.
%A Pollet, T.
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Bit-rate sensitivity of filter-bank-based VDSL transmission to timing errors
%X The performance degradation of filter-bank-based multicarrier transmission due to timing errors is investigated. The receiver is made of a fractionally spaced linear or decision-feedback equalizer designed for some sampling phase. The actual sampling phase is different and the impact of the difference on the performance is investigated. Sampling phase offset and jitter are considered. Besides, assuming the sampling phase error can be estimated the efficiency of various types of interpolation is investigated.
%K filter banks
%K multicarrier transmission
%K synchronization
%K timing errors
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%! IEEE Trans. Commun.
%V 49
%N 2
%P 375-384
%D 2001
%@ 0090-6778 (ISSN)
%@ 1558-0857 (e-ISSN)
%* peer-reviewed
%D 2001
%U Handle: http://hdl.handle.net/2078.1/42892
%R 10.1109/26.905901
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Vanhoenacker-Janvier, Danielle
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Coverage analysis of a stratospheric communication system
%X An original method for predicting the performance of upcoming stratospheric communication systems is presented. The prediction is based on a physical-statistical model of the built-up channel, used in combination with existing models of the tropospheric mechanisms. The physical nature of the approach allows the statistics of fade and BER to be obtained as a function of any input parameter, such as the size of the target area, the platform height or the area characteristics. Simulations provide, for example, values of BER achieved over a certain percentage of area during a given percentage of time, as a function of the ground range right below the platform. Various system procedures. such as error correction and power control, are also investigated.
%K ICTEAM:COMM
%G Anglais
%J IEE Proceedings - Microwaves, Antennas & Propagation
%B IEE Proceedings - Microwaves, Antennas & Propagation
%! IEE Proc.-Microw. Antennas Propag.
%V 148
%N 1
%P 45-49
%D 2001
%@ 1350-2417 (ISSN)
%* peer-reviewed
%D 2001
%U Handle: http://hdl.handle.net/2078.1/42808
%R 10.1049/ip-map:20010226
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Vanhoenacker-Janvier, Danielle
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Coverage modelling of high-altitude platforms communicaton systems
%X Based on a physical-statistical model. an analytical mrthod is developed to predict the coverage of IMT-2000 communication systems based on high-altitude platforms. First, the general modelling approach is presented, together with L-band experimental validation. The particular case of high-altitude platforms is then analysed in the framework of the IMT-2000 standard.
%K ICTEAM:COMM
%G Anglais
%J Electronics Letters
%B Electronics Letters
%! Electron. Lett.
%V 37
%N 2
%P 119-121
%D 2001
%@ 0013-5194 (ISSN)
%@ 1350-911X (e-ISSN)
%* peer-reviewed
%D 2001
%U Handle: http://hdl.handle.net/2078.1/42937
%R 10.1049/el:20010084
%0 Journal Article
%9 Article de recherche
%A Guenach, M.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL)
%T Downlink performance analysis of a BPSK-based WCDMA using conventional rake receivers with channel estimation
%X In this paper, we consider the downlink of a Universal Mobile Telecommunication System terrestrial radio access-wideband code division multiple access (UTRA-WCDMA) system and we investigate the performance of the conventional rake receiver. A multipath slowly Rayleigh fading channel is assumed. For the purpose of channel tap weight estimation, a common control physical channel, that is either serial or parallel multiplexed with the dedicated physical channels, is used. The receiver sensitivity to imperfect knowledge of the path delays, to the number of pilot symbols, and to the power ratio of pilot to data channels is also investigated. The system performance is evaluated by means of bit-error rates (BERs) derived using quadratic forms and characteristic functions for a BPSK modulation. The mean-squared estimation error (MSEE) of the channel tap weights is also computed and compared to the classical Cramer-Rao Lower Bound (CRLB). The mutual interference between pilot and data symbols is taken into account.
%K code division multiple access
%K diversity
%K parameter estimation
%K rake reception
%G Anglais
%J IEEE Journal on Selected Areas in Communications
%B IEEE Journal on Selected Areas in Communications
%! IEEE J. Sel. Areas Commun.
%V 19
%N 11
%P 2165-2176
%D 2001
%@ 0733-8716 (ISSN)
%@ 1558-0008 (e-ISSN)
%* peer-reviewed
%D 2001
%U Handle: http://hdl.handle.net/2078.1/42446
%R 10.1109/49.963803
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Vanhoenacker-Janvier, Danielle
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Infinitesimal diffraction model for mobile wireless communication systems
%X A new diffraction method that yields realistic simulations of the mobile channel in built-up areas is presented. The new model, using UTD-based edge equivalent currents, allows for integrating the finite dimension of building wedges in the field estimation, A comparison with 1.6GHz experimental data shows good agreement in terms of level-crossing rate, in contrast to results obtained with the basic UTD.
%K ICTEAM:COMM
%G Anglais
%J Electronics Letters
%B Electronics Letters
%! Electron. Lett.
%V 37
%N 13
%P 856-858
%D 2001
%@ 0013-5194 (ISSN)
%@ 1350-911X (e-ISSN)
%* peer-reviewed
%D 2001
%U Handle: http://hdl.handle.net/2078.1/42635
%R 10.1049/el:20010550
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Paulraj, Arogyaswami J.
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%+ Stanford University - ISL
%T Physical model for broadband wireless channels
%K ICTEAM:COMM
%G Anglais
%J Electronics Letters
%B Electronics Letters
%V 37
%N 19
%P 1195-1197
%D September
%@ 0013-5194 (ISSN)
%@ 1350-911X (e-ISSN)
%* peer-reviewed
%D 2001
%U Handle: http://hdl.handle.net/2078.1/88486
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Vanhoenacker-Janvier, Danielle
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Propagation modeling and system strategies in mobile-satellite urban scenarios
%X Land mobile satellite (LMS) systems require fade countermeasure techniques since they suffer from limited fade margins and severe channel degradations. In the view of complete recent statistical models for LMS systems in urban areas, this paper deals with several specific mobile satellite urban configurations, such as a long straight street lined on both sides by buildings and a crossroad, Propagation effects are modeled as time series of received power by means of a ray-tracing method, which is used in combination with an orbit generator. The time series results are then postprocessed to simulate the impact of propagation mechanisms and satellite motion on fade mitigation techniques, satellite handover, and diversity. This original approach inherently accounts for the correlation between a number of very different but simultaneous effects that influence system performance, Exemplary results are finally discussed to stress the capability of the time-series approach.
%K communication system performances
%K satellite mobile communication
%K urban areas
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Vehicular Technology
%B IEEE Transactions on Vehicular Technology
%! IEEE Trans. Veh. Technol.
%V 50
%N 2
%P 422-429
%D 2001
%@ 0018-9545 (ISSN)
%@ 1939-9359 (e-ISSN)
%* peer-reviewed
%D 2001
%U Handle: http://hdl.handle.net/2078.1/42735
%R 10.1109/25.923054
%0 Journal Article
%9 Article de recherche
%A Guenach, M.
%A Vandendorpe, Luc
%+ Université catholique de Louvain (UCL)
%T Tracking performance of DA and DD multiuser timing synchronizers for short code DS-CDMA systems
%X We consider a direct-sequence code-division multiple-access system operating over frequency-selective multipath and slowly Rayleigh fading channels. In order to implement RAKE reception, the delays of the different paths have to be estimated and the estimates have to be updated. We extend interference mitigation to this estimation problem and design timing recovery schemes accounting for the intersymbol interference and the multiple-access interference present in the signal. Starting from the maximum likelihood approach, we derive data-aided and decision-directed early-late synchronizers and study their tracking performance. The advantage of the interference mitigating synchronizer is illustrated. The sensitivity of the synchronizer to imperfect knowledge of path gains and to near-far situations is also investigated.
%K code-division multiple access
%K data aided
%K decision directed
%K delay estimation
%K diversity reception
%K maximum likelihood estimation
%K synchronization
%K timing jitter
%K tracking loops
%G Anglais
%J IEEE Journal on Selected Areas in Communications
%B IEEE Journal on Selected Areas in Communications
%! IEEE J. Sel. Areas Commun.
%V 19
%N 12
%P 2452-2461
%D 2001
%@ 0733-8716 (ISSN)
%@ 1558-0008 (e-ISSN)
%* peer-reviewed
%D 2001
%U Handle: http://hdl.handle.net/2078.1/42225
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Raynaud, Lidwine
%A Clerckx, Bruno
%A Vanhoenacker-Janvier, Danielle
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T A deterministic model for third generation mobile communication systems in urban environments
%X This paper describes a deterministic model which simulates the radiowave propagation for UMTS in urban areas. The model is based on a UTD ray-tracing tool, using the mirror method. Meanwhile, channel impulse responses (CIRs) have been measured in order to validate the ray-tracing tool. Measurements have been carried out at 1.87 GHz in a street of Louvain-la-Neuve (Belgium) by means of a wideband channel sounder. Simulated and experimental results are presented and compared quite satisfactorily in spite of several limitations.
%K ICTEAM:COMM
%G Anglais
%J Acta Technica Belgica. Revue H F: Electricite Courants Faibles. Electronique Telecommunications
%B Acta Technica Belgica. Revue H F: Electricite Courants Faibles. Electronique Telecommunications
%! Rev. HF (Belgium)
%N 3
%P 49-57
%D 2000
%@ 0035-3248 (ISSN)
%* peer-reviewed
%D 2000
%U Handle: http://hdl.handle.net/2078.1/66252
%Z Oestges, C.; Raynaud, L.; Clerckx, B.; Vanhoenacker-Janvier, D.;Microwave Lab., UCL, Louvain-la-Neuve, Belgium
%0 Journal Article
%9 Article de recherche
%A Louveaux, Jérôme
%A Vandendorpe, Luc
%A Cuvelier, Laurent
%A Pollet, Thierry
%+ Université catholique de Louvain (UCL) - SST/ICTM/ELEN - Pôle en ingénierie électrique
%T An early-late timing recovery scheme for filter-bank-based multicarrier transmission
%X This paper examines a decision-directed timing recovery scheme for filter-bank-based multicarrier transmission. The symbol synchronizer is obtained from a maximum-likelihood approach and uses the digital equalization filters. The algorithm is first derived, the performances of the scheme (timing offset and timing jitter) are then computed, and computational results are provided for high bit-rate transmission over copper wires. Finally, different improvements are discussed.
%K Filter banks
%K Signal filtering and prediction
%K Signal receivers
%K Timing jitter
%K Filter banks
%K Multicarrier transmission
%K Single-input multi-output linear equalizer
%K Timing error detector
%K Digital filters
%K Multicarrier transmission
%K Synchronization
%K Timing jitter
%K Algorithms
%K Bit error rate
%K Error detection
%K Maximum likelihood estimation
%K Multicarrier modulation
%G Anglais
%J IEEE Transactions on Communications
%B IEEE Transactions on Communications
%V 48
%N 10
%P 1746-1754
%D 2000
%@ 0090-6778 (ISSN)
%* peer-reviewed
%D 2000
%U Handle: http://hdl.handle.net/2078.1/136961
%R 10.1109/26.871399
%0 Journal Article
%9 Article de recherche
%A Oestges, Claude
%A Vanhoenacker-Janvier, Danielle
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Experimental validation and system applications of ray-tracing model in built-up areas
%X A ray-tracing model based on the uniform theory of diffraction is briefly described. A comparison between simulation and experimental results at 12.5 and 30GHz is presented. Since measurements were carried out in winter and late summer, they also highlight the effect of vegetation at these frequencies. Finally, the ray-tracing tool is applied to the characterisation of an urban channel at several frequency bands.
%K ICTEAM:COMM
%G Anglais
%J Electronics Letters
%B Electronics Letters
%! Electron. Lett.
%V 36
%N 5
%P 461-462
%D 2000
%@ 0013-5194 (ISSN)
%@ 1350-911X (e-ISSN)
%* peer-reviewed
%D 2000
%U Handle: http://hdl.handle.net/2078.1/43666
%R 10.1049/el:20000368
%0 Journal Article
%9 Article de recherche
%A Chevreuil, Antoine
%A Loubaton, Philippe
%A Vandendorpe, Luc
%T Performance of general transmitter induced cyclostationarity precoders: analysis based on a MMSE-DF receiver
%X The effect of a filterbank precoder on Shannon's capacity is considered. Simple asymptotic expressions are derived. Analytical comparisons between various schemes that show how crucial the excess bandwidth factor is are provided. The results are illustrated by computer simulations
%K ICTEAM
%K ICTEAM:SIGN
%K ICTEAM:COMM
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%V 48
%N 11
%P 3072-3086
%D November 2000
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2000
%U Handle: http://hdl.handle.net/2078/122997
%R 10.1109/78.875465
%0 Journal Article
%9 Article de recherche
%A Labeau, F.
%A Vandendorpe, Luc
%A Macq, Benoît
%+ Université catholique de Louvain (UCL) - FSA/ELEC - Département d'électricité
%T Structures, factorizations, and design criteria for oversampled paraunitary filterbanks yielding linear-phase filters
%X We present here a special class of oversampled filterbanks (FBs), namely, paraunitary FBs with linear-phase filters. We propose some necessary conditions for the existence of such banks, based on the repartition between type VII and type III/IV linear-phase filters in the bank. For a subset of these FBs, we develop a factorization that leads to a minimal implementation, as well as a direct parameterization of the FBs in terms of elementary rotation angles. This factorization is applied to some design examples, with two different optimization criteria: coding gain and reconstructibility of lost coefficients.
%K filterbanks
%K filter design
%K multirate processing
%K oversampled filterbanks
%G Anglais
%J IEEE Transactions on Signal Processing
%B IEEE Transactions on Signal Processing
%! IEEE Trans. Signal Process.
%V 48
%N 11
%P 3062-3071
%D 2000
%@ 1053-587X (ISSN)
%@ 1941-0476 (e-ISSN)
%* peer-reviewed
%D 2000
%U Handle: http://hdl.handle.net/2078.1/43248
%R 10.1109/78.875464