Multipath TCP for user cooperation in LTE networks

User cooperation exploits nearby mobile devices as relays and offers an opportunity to enable multipath transmission for multi-homed mobile devices, even when there is no multiple access coverage. MPTCP by Internet Engineering Task Force is a promising solution to support simultaneous delivery of TCP packets over multiple paths. One key component of MPTCP is the coupled congestion control algorithm, which aims to aggregate available bandwidths of multiple paths while avoiding aggressive behavior to regular single-path TCP traffic sharing the paths. However, we find out that in a user cooperation scenario, the throughput of local single-path traffic of relays can be severely degraded by forwarding subflows of MPTCP, which can jeopardize the motivation for user cooperation. In this article we propose extensions to the congestion control of MPTCP for a user cooperation scenario in the Long Term Evolution network. The local traffic at relays can be controlled by regular TCP and more generic additive-increase and multiplicativedecrease protocols. Simulation results demonstrate that our extensions do not degrade performance for adding MPTCP subflows to local traffic, and thus better promote user cooperation.