Tuning Multipath TCP for Interactive Applications on Smartphones

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. On smartphones, user experience is always a compromise between network performance and energy consumption. However, the Multipath TCP implementation in the Linux kernel was mainly tuned for bandwidth aggregation and often wakes up the cellular interface by creating a path without sending data on it.In this paper, we propose, implement and evaluate MultiMob, a solution providing fast handover with low cellular usage 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. Our results show that MultiMob provides similar latency as the standard Linux implementation while significantly lowering the cellular usage.