Performance Enhancement of Transmission Control Protocol over Wireless Ad-hoc Networks

Mobile Ad Hoc Network (MANET) is a multihop wireless network in which any node can connect to any other node other node without a centralized infrastructure. The nodes participating in a MANET operate both as hosts and as routers. TCP is mainly developed for wired networks and it is required to adapt the famous protocol to work perfectly in wireless networks.TCP implements both flow control and congestion control. Flow control prevents the TCP receiver’s buffer from being overflowed while congestion control avoids congestion collapse within the network. The congestion control continuously probes the network for resources. Some versions of TCP use the additive increase multiplicative decrease algorithm (AIMD), to speed up loss recovery and ensure network stability. An alternative algorithm to AIMD is the equation-based congestion control. The latter attempts to reproduce TCP behaviour analytically, but an accurate modelling is too hard to achieve. This is a subject of great interest in the research community nowadays. In MANET the standard TCP when works on multi-hop faces many problems related to nature of wireless media like performance degradation and unstable connectivity. This research presents a study for a modified TCP protocol in order to enhance the behaviour of the protocol in Ad-hoc wireless networks. In this paper two modifications to the standard TCP were proposed by adjusting TCP's behaviour during slow start and congestion avoidance phases. The throughput of the proposed protocols has increased over the throughput of the standard TCP protocol. Glomosim simulator was used which is one of known simulators for Adhoc wireless networks. Keywords— TCP, Ad-hoc, MANET, AIMD.