Congestion Control Algorithm For Semi-tcp Based On Rts/cts In Multi-hop Wireless Networks

TCP(Transmission Control Protocol) with the window-based congestion control algorithms has achieved enormous success in the Internet. However when it is used in multi-hop wireless networks, TCP performs poorly as reported in the literature. This situation becomes even worse in mobile networks mainly due to its misjudgment and slow reaction to congestion status in the network. To solve these problems, Semi-TCP is proposed, which suggests a hop-by-hop congestion control by decoupling congestion control from the transmission layer, and is more appropriate for multi-hop wireless networks.However, how to effectively implement Semi-TCP's hop-by-hop congestion control algorithm has not been studied sufficiently. This dissertation focuses on such a congestion control algorithm using the IEEE 802.11 DCF RTS/CTS handshake protocol. The main contributions include: 1) the study of a method to judge congestion status in multi-hop wireless networks, 2) an investigation of the deadlock problem for the hop-by-hop congestion control for Semi-TCP along with a solution, 3) an implementation of the hop-by-hop congestion control algorithm with the IEEE 802.11 DCF RTS/CTS in NS2, and 4) the evaluation of this congestion control algorithm with simulation study. Simulation results show that this congestion algorithm can make Semi-TCP to outperform TCP-AP (which is a better proposal to improve TCP in wireless networks) by 71% in terms of throughput at most.