Evaluation of End-to-End TCP performance over WCDMA

this article investigates the end-to-end TCP performance in the scenario where WCDMA is employed as the access link. Unlike previous work, we incorporate the impact of Internet loss rate and delay into the study. The performance of TCP over WCDMA is studied from several aspects: the TCP protocol configurations, the different variant of TCP protocols, the interaction of TCP and RLC layer protocols, and Impact of core network in terms of delay and loss rate. Finally, a novel TCP proxy concept is proposed in order to improve the TCP performance in large delay-bandwidth product scenario. The simulation results shows that: firstly, for small file size, such as web pages, the TCP initial slow start can harm the throughput of users who are allocated high channel bit rates DCH channels; Secondly, a large TCP slow start initial counter (larger than 1 maximum segment size) can improve the throughput of TCP in the slow start phase; Thirdly, there is strong correlation between TCP and RCL layers protocols: in general the more reliable is the RLC layer, the more benefit can be obtained from TCP throughput. However, a too large RLC MaxDAT will lead to TCP timeout thus harm TCP throughput. Finally, it is showed that the novel TCP proxy brings significant TCP performance gain in the high delay bandwidth product scenario while only a small improvement in low delay bandwidth product scenario. Keywords-component; TCP performance; WCDMA; RLC layer; TCP proxy