Modeling And Analysis On The Performance Of Network Coding-based TCP In Wireless Networks

In wireless networks, the performance of traditional TCP degrades significantly due to random packet losses which are caused by the highly dynamic topology and limited bandwidth of wireless networks. In order to improve TCP performance in wireless networks, researchers proposed different schemes, including link layer solutions, split connection solutions, end to end solutions and proxy agent solutions, etc. But all the schemes either damage the end to end feature of TCP, or damage the independence of different layers in the protocol stack. Few of them can solve the TCP performance degradation problem in wireless networks effectively.J.K.Sundararajan et.al proposed a new protocol called TCP/NC based on network coding. The main idea is to introduce a network coding layer between TCP and IP layer. With the redundant information of the coded packets, non-congestion caused losses can be masked and the calling of the unnecessary congestion control mechanism can be avoided. The authors verified the performance of TCP/NC with simulation and also gave a first-hand analysis. However, many factors closely related to the throughput of TCP/NC, such as packet loss rate, redundancy factor and coding window, etc, were not considered.To verify the effectiveness of TCP/NC, we first compared TCP/NC with TCP Reno and TCP Vegas both in simulation and theoretical analysis. Then we made a comprehensive evaluation the TCP/NC protocol with the Markov model and queuing theory. We also compared the results of theoretical analysis and simulation to verify the validity of the modeling process. The results show that our model is much more reasonable. Finally, we analyzed the performance of TCP/NC and proposed the possible optimization direction of the network coding.