无线网络中优化TCP性能的网络编码方法研究

Research on Network Coding to Optimize Performance of TCP in Wireless Networks

网络编码的出现为改进网络的传输性能提供了新的方法。J.K.Sundararajan等人将网络编码技术与传输控制协议相结合,提出了基于网络编码的TCP/NC协议,其在改进无线网络中传统TCP的性能方面取得了明显效果。但该协议及其改进协议存在的数据传输和解码操作同步性问题会严重影响TCP/NC性能。提出的改进协议TCP/NCW根据解码时间调节解码窗口,以确保数据传输和解码操作同步,从而获得更好性能。运用排队论分析了TCP/NCW最优解码窗口的存在性。在NS2中的仿真结果表明,在静态场景和动态场景下TCP/NCW的吞吐率比TCP/Vegas和TCP/NC有显著提高,同时也具有较好的公平性。

The emergence of network coding provides a new method for improving TCP performance in wireless net- work. J. K. Sundararajan et al. proposed a new protocol called TCP/NC based on network coding combining the network coding and transmission control protocol, which achieves remarkable results in improving the performance of TCP in wireless network. But the synchronism problem in data transmission and decoding operation may seriously affect the performance of TCP/NC and its modified protocol is not considered. To address this issue, a revised protocol TCP/ NCW was proposed in this paper. We introduced the decoding window adjustment scheme based on TCP/NC. In TCP/ NCW, the decoding window is adjusted according to the decoding time and will finally reach an optimal window size. This scheme can ensure the synchronization of data transfer and decoding operation. Therefore, this scheme can achieve better performance. We used the queuing theory to analyze the existence of the optimal decoding window of TCP/NCW. The simulation results with NS2 show that TCP/NCW achieves significant improvement in throughput compared with both TCP/Vegas and TCP/NC in different scenarios, without prejudice of fairness.