Research Of Optimizing The Wireless TCP

In wireless networks, many application protocols such as Wide Web Internet, FTP, E-mail and Telent are built on TCP protocol. Because the original TCP protocol is designed for the wired network, so the TCP protocol is suit for good quality links. However, in the wireless networks, the network topology and the channel conditions are always changing, and the bandwidth resources are limited, so the output of traditional TCP declines obviously. CTCP is a new and reliable transport protocol using network coding to provide robustness against losses and improve the throughputs.This paper studies the following three aspects of the CTCP protocol.1) Establish an analysis model for CTCP system. Firstly, by solving the equivalent CTCP link loss rate, without considering the impact of delay from coding and decoding process and the limit of the receive buffer, we build the CTCP system analysis model based on PFTK model, and get the effective send rate as a function of loss rate and RTT. Then we use the model to show that the redundant package is the key reason for that CTCP performs much better than TCP over the lossy link.2) Improve the CTCP coding algorithm. In order to reduce the number of redundant packets for CTCP protocol, we propose a variable-length block coding algorithm. As TCP communication is peer to peer, we use partly random linear coding algorithmto reduce the CTCP coding complexity. Finally, we design a variable-length portion random linear coding algorithm which is suitable for CTCP protocol.3) Provide a new implement method for CTCP protocol. Traditional CTCPimplement method is quite different from the TCP implement method. In this paper we design a new CTCP implement method with the SACK technique, by which the lost packets are directly retransmitted, so that the recoding process is not necessary and the change in the TCP protocol stack is smaller.