提升无线网络TCP公平性的跨层机制研究

A Cross-layer Scheme to Improve TCP Fairness in wireless networks

主要研究多跳无线AdHoc网络中TCP业务的公平性问题,分析了造成TCP业务不公平的多种原因,并验证MAC层的介质访问延迟能够反映出无线信道的拥塞程度,在此基础上提出基于MAC层传输延迟的邻居区域随机提前检测机制,即Mac-layer Delayand Neighborhood Random Early Detection(MDNRED)。该机制主要包括四部分测量MAC延迟;判断拥塞发生位置;发出拥塞通知;节点计算丢包概率。仿真试验证实,在特定场景下MDNRED机制能够在保证一定吞吐率的基础上有效提升各条TCP流的公平性。

This paper focus on the improvement of TCP fairness in multi-hop wireless ad hoc networks.The reasons of TCP unfairness in ad hoc networks and the relationship between packet delay and channel utilization are analyzed.MDNRED has been proposed to improve TCP fairness.In this scheme, the MAC layer delay is used to detect congestion and to notify the nodes which use too much channel dropping their packets and giving the expressed node chance to transmit.There are four parts in this scheme, measuring MAC delay, detecting congestion, sending congestion notification and accounting drop probability.At last, the performance of MDNRED has been approved by the simulation and experiment.