An Analytical Model and Performance Evaluation of Transport Protocols for Wireless Ad Hoc Networks

Performance of Transport Control Protocol (TCP), designed for wired networks, degrades significantly over wireless links and provides abysmal throughput because TCP assumes that all packet losses are caused by congestion. However, in wireless ad-hoc networks, packet losses could be due to several reasons such as link loss, node mobility, and faulty nodes, to name a few. Current techniques for improving TCP do not consider packet drops by faulty nodes. We propose a novel idea of distinguishing between wireless and congestion losses by using the concept of Kleinrock\´s "power" metric. Based on this idea we propose two reliable transport protocols, TCP- Monet and TCP-Sec, that classify packet losses based on current connection status and react accordingly. TCP-Monet distinguishes between congestion and wireless losses, while TCP-Sec distinguishes amongst losses due to congestion, wireless errors, and packet drops by faulty nodes. We develop an analytic model of throughput in the presence of wireless losses, congestion losses, and packet drops by faulty nodes. We conducted simulation experiments using the ns-2 simulator and our experiments demonstrate that this model is able to more accurately predict throughput when there are wireless losses and faulty nodes.