Resource Efficient TCP: Reducing Contention-Induced Spurious Timeouts in QoS -Aware MANETs

The bandwidth is one of the most precious resources in mobile ad hoc networks (MANETs); their network protocols should therefore be able to achieve an increase in efficiency of bandwidth utilization. TCP, which implements flow control to regulate the network traffic, plays a significant role in determining the workload of the network. However, spurious TCP retransmissions can increase the link utilization and consequently limiting the amount of spare bandwidth available as extensively reported in the literature. This problem is exacerbated by the presence of high priority traffic and traffic differentiation introduced in IEEE 802.11e. In this paper, we focus on the optimization of TCP for resource efficiency, by limiting the number of contention-induced retransmissions. Using feedback from the MAC layer, the TCP layer can be notified of the medium contention state and adjusts its retransmission timer accordingly. Our simulation results demonstrate the effectiveness of our proposal in various scenarios. Our proposal achieves a gain of 15% in resource utilization and reduces power consumption by retransmitting fewer segments; it also improves TCP performance in terms of goodput and end-to-end delay.