In this thesis, we propose several enhancement modules to Multipath TCP (MPTCP) so as to support stable and efficient multipath transmission with user cooperation in the Long Term Evolution (LTE) network. Specifically, we aim to 1) provide a stable aggregate throughput to the upper-layer applications; 2) guarantee a steady goodput, which is the real application-layer perceived throughput; and 3) ensure that the local traffic of the relays is not adversely affected when the relays are forwarding data for the destination. Firstly, we propose a subset-sum based relay selection (SSRS) module to achieve a stable aggregate throughput with MPTCP in the user cooperation scenario. Secondly, two independent and complementary modules, adaptive congestion control (ACC) and differentiated packet forwarding (DPF), are developed to improve the goodput based on the stable aggregate throughput provided by SSRS. Thirdly, a bandwidth sharing module extends the congestion control algorithm of MPTCP to ensure that the throughput of the local traffic at the relays is not degraded by the forwarding traffic for the destination. As the foundation of ACC and DPF, the SSRS and bandwidth sharing modules can protect the local traffic of the relays and provide a stable aggregate throughput so that ACC and DPF can further improve the goodput perceived at the application layer. To evaluate the performance of the proposed extensions to MPTCP, we implement an MPTCP module of ns-3 and extend the LTE network module of ns-3 to support user cooperation among mobile devices. The performance of the proposed solutions is extensively evaluated in various scenarios. The simulation results demonstrate that the proposed modules can achieve a stable aggregate throughput and significantly improve the goodput by 1.5 times on average. At the same time, the results also show that our extensions can well respect the local traffic of the relays and motivate the relay users to provide the relaying service.
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