The Research Of TCP Performance Over Wireless Network

In the Internet, TCP is the primary transport protocol. It performs well in traditional networks where congestion is the primary cause of packets loss. However, wireless networks also suffer from significant losses due to bit enors, TCP responds to all losses by invoking congestion control and avoidance algorithms, resulting in the degraded end-to-end performance unnecessarily.Firstly three wireless networks-satellite WAN, 802.11 LAN and 802.15.4 PAN and the challenges TCP ment are introduced. Then the dissertation reviews acknowledgement mechanism and congestion avoidance mechanism in TCP protocol, introduces three classical version of TCP- TCP Tahoe, TCP Reno and TCP Vegas. Following the dissertation studies some ideas which improve the performace of TCP protocol in random enor wireless links, an improved congestion control mechanism that is able to deal with random loss effectively. The improved mechanism differs from the conventional TCP in a major way: it monitors the congestion level using an subsection estimation algorithm and uses the knowledge to refine the congestion control algorithm of TCP atempting to stay longer in an operating region in which the bandwidth is fully utilized.Secondly, network tested experiments have been conducted and they consistently show that improved mechanism can achieve significant performance improvement over Reno in many different scenarios. Throughput improvement of as high as 100% is typical in the satellite WAN seting with random loss at 10^-4, throughput improvement of as high as 20% is typical in the 802.11 LAN setting with random loss at 10"2, throughput improvement of as high as 5% is typical in the 802.15.4 PAN setting with random loss at 10^-2. The performance of improved mechanism has direct ratio with latance and bandwidth in wireless networks. It can coexist with concurrent TCP protocol and UDP protocol connections without degrading the performance of TCP or UDP connections. And it can be deployed easily with only minor modifications of the sender-side algorithm.At last, upon mobile Ad hoc network, one transport protocol has been picked out. The component of protocol is analyzed, the application of this protocol in internet is discussed.