Subset-sum based relay selection for multipath TCP in cooperative LTE networks

Pooling mobile devices in vicinity as a cooperative community offers an opportunity to enable multipath transmission for multi-homed mobile devices, even when there is no multiple access coverage. Nonetheless, the available bandwidth provided by relays can be highly varying due to a range of factors such as wireless channel fading and dynamic local traffic load at relays. As a result, it is challenging to maintain a stable multipath aggregate throughput over relays. In this paper, we propose an enhancement module within the application layer for a cooperative community in the Long Term Evolution (LTE) network. Our extension is based on the standardized multipath transport control protocol (MPTCP) [1]. Based on relay bandwidth monitoring, a dynamic relay selection algorithm is developed for adding and deleting paths so as to ensure a stable aggregate throughput in a highly varying environment. The proposed relay selection algorithm is based on a fully polynomial-time subset-sum approximation [2]. Extensive simulations are conducted to evaluate the proposed solution in different background traffic patterns. The simulation results well demonstrate the strengths in minimizing throughput outage, the number of active subflows, and performance variation.