无线接入网络中TCP流的上下行信道公平算法

Improving the Up/Down TCP Fairness in Wireless Access Network

在无线接入网络中,上行TCP流会极大地压制下行TCP流,导致严重的上下行信道TCP流不公平问题.本文指出TCP流的ACK包在接入节点下行缓存中的侵占性是上下行TCP不公平问题的直接原因,从限制缓存大小的新角度提出了MBA(Maximum Buffer for ACKs)算法.MBA算法基于上下行TCP流的不公平比例和缓存大小的关系,自适应地调节ACK包的最大缓存空间.理论分析和仿真实验结果表明MBA算法不但能通过限制ACK包的缓存空间实现上下行TCP流公平,还能通过减少无线信道ACK包传输概率提高网络总有效吞吐率.

In wireless access networks,the wireless service is biased toward the uplink TCP flow and the downlink TCP flow tends to starve.This paper analyzes the TCP unfairness problem and proposes a buffer sizing algorithm,called MBA（Maximum Buffer for ACKs）.Based on the relation between the TCP unfairness and buffer sizing,MBA algorithm adjusts the maximum size of buffer allocated for the ACK packets.Analysis and simulation results show that,MBA not only improves the fairness greatly by limiting the buffer for ACK packets,but also achieves higher total network goodput by reducing the channel occupying time of ACK packets.