通过链路层ARQ提高无线环境中的TCP吞吐量

提出了一种用于提高无线环境中传输控制协议(TCP)性能的链路层选择性重传的改进方案——自适应选择性重传。本方案借助于每个数据包在数据链路层被拆分成多个无线帧这一特点,对包中所有帧的重传次数之和进行限定,使得该和可以根据各个帧的需求进行自适应的分配。推导了采用该方案时无线链路的误包率和包的传输时延的表达式。通过引入Padhye的TCP吞吐量模型,分析了采用自适应选择重传方案系统的TCP吞吐量。仿真结果表明,与传统方案相比,自适应选择重传方案在高误帧率环境下以较低的误包率、略大的传输时延获得了较高的TCP吞吐量。

Improvement of TCP Throughput in Wireless Environment by Link Layer ARQ

A modified link layer selective repeat automatic repeat qequest (ARQ) scheme is proposed to improve transport control protocol (TCP) performance over wireless networks--adaptive selective repeat ARQ(ASR-ARQ). According to the feature of every high layer packet being fragmented into several frames at link layer, ASR-ARQ limits the maximum retransmission number per packet and can adaptively allocate retransmission number to frames belonging to the same packet. The link layer packet error rate and transmission delay are derived to evaluate this scheme. The Padhye's TCP throughtput model is also used to evaluate the TCP performance of systems using ASR-ARQ. Numerical results demonstrate ASR-ARQ can achieve much lower packet error rate with slightly longer delay and higher TCP throughput than the conventional scheme.