Strategies to improve the performance of TCP in mobile ad hoc networks

Abstract

Applying TCP directly in MANETs cannot achieve satisfactory performance: throughput degradation and severe unfairness problem. Many strategies are proposed to improve the TCP throughput. The unfairness problem is also widely studied with few resolving strategies proposed. As most of the strategies to improve TCP throughput are implemented with TCP-Reno and our studies show that TCP-Vegas achieves better performance than TCP-Reno in MANETs, we apply Vegas in MANETs. Applying Vegas in MANETs would face the re-routing problem which will cause very low throughput. Correspondingly, we propose the Vegas Routing Interaction Strategy (VRIS) to solve the problem to effectively improve the Vegas throughput in the mobile scenarios. VRIS is implemented with both DSR and AODV. The throughput improves about 10% on average and up to 223.01%. It is hard to define fairness in mobile scenarios. Thus, we propose the Adaptively Setting Congestion Window Limit (ASCWL) strategy to solve the severe unfairness problem in static scenarios. As the strategies to solve the unfairness problem are rare, we implement ASCWL with both Reno and Vegas. ASCWL can improve the fairness index by up to 89.21% and the overall throughput also has improvement. To summarize, we propose to apply Vegas in MANETs. With re-routing problem resolved and appropriate congestion window limit setting, Vegas performance in MANETs can achieve visible improvement.