Every Millisecond Counts: Tuning Multipath TCP for Interactive Applications on Smartphones

De Coninck, Quentin [UCL] Bonaventure, Olivier [UCL]

Multipath TCP enables smartphones to simultaneously use both WiFi and LTE to exchange data over a single connection. This provides bandwidth aggregation and more importantly reduces the handover delay when switching from one network to another. This is very important for delay sensitive applications such as the growing voice activated apps. In this paper, we explore different techniques to tune Multipath TCP for interactive applications. On smartphones, user experience is always a compromise between network performance and energy consumption or battery lifetime. We first explore the open-source Multipath TCP implementation in the Linux kernel. Our measurements indicate that Linux needs to better take energy consumption into account. We then propose, implement and evaluate MultiMob, a solution providing fast handover with low energy consumption for interactive applications. MultiMob relies on three principles. First, it delays the utilization of the LTE network. Second, it allows the mobile to inform the server of its currently preferred wireless network. Third, MultiMob extends the Multipath TCP handshake to enable immediate retransmissions to speedup handover. We implement MultiMob on Android 6 smartphones and evaluate its benefits by using both microbenchmarks and in the field measurements.