Impact of edge diffraction on the performance of land mobile satellite systems in urban areas

This paper highlights the influence of edge diffraction on the performance of land mobile satellite (LMS) systems in urban environments. The channel is modelled using a ray-tracing software which evaluates the complex signal received by a mobile terminal moving in a three-dimensional area. This method takes into account the line-of-sight ray plus various contributions generated by reflection from ground and wall surfaces as well as by diffraction on building edges. As diffraction from both horizontal and vertical edges appears to be one of the most significant mechanisms, precise modelling is developed. Single diffraction from an edge of finite length is accounted for by means of a UTD-based edge equivalent current method. Double diffraction is also implemented, but is found to be negligible. The ray-tracing method is applied to produce a time series in a typical urban environment. A canonical wideband scenario is also investigated and predictions of system performance are achieved. It is shown that significant impairments may be attributed to edge diffraction mechanisms.