Performance evaluation of transmission control protocol in mobile ad hoc networks

Transmission Control Protocol (TCP) is widely accepted, reliable end-to-end transport layer communication protocol. It has self generating error control mechanism to achieve reliability using error correction. It also has flow control scheme to avoid network congestion using window mechanism. TCP is tuned to perform well in traditional wired networks, where the packet losses are primarily due to congestion. However, with the increasing trend and developments in wireless communication, there is an immense need of adapting TCP to the wireless environment. Packet loss in wireless networks could be due to bit error rate (BER), link failure or handoffs. If standard TCP is applied on such wireless networks without any modification, it would lead to performance degradation. To address these problems, many solutions have been proposed for TCP enhancements over wireless networks. In this paper, performance of New Reno, Selective Acknowledgements (SACK), Explicit Congestion Notification (ECN) and Westwood has been analyzed through simulations. Performance has been measured on the basis of average throughput, packet loss ratio and average end to end delay in wireless environment in three different scenarios; mobility (variable speed), link loss and both mobility and link loss. Results show that New Reno has more stable and consistent results in the absence of congestion, otherwise ECN performs better.