Enhancing TCP performance in multihop ad hoc networks

In multi hop ad hoc networks, performance of TCP degrades due to various reasons such as MAC contention, congestion, large round-trip time variations. In multi hop ad hoc network the over-injection of conventional TCP window mechanism results in severe contentions, and medium contention causes congestion. In multi hop ad hoc network, delay variance at MAC results in large round trip time variations. This paper proposes an Adaptive congestion window mechanism presents an enhancement in TCP round-trip time estimation using the information from the routing layer. This scheme reduces spurious round trip timeout and also reduces unnecessary retransmissions which are caused by link failures. This method significantly improves throughput performance of the network. Also, the round-trip time (RTT) is split into two parts: 1) congestion RTT and 2) contention RTT. Congestion RTT is used to determine BDP. Contention RTT is used to determine the contention situation. Simulation results show the improvements in TCP obtained through this approach in terms of throughput and delay performance.