Improving TCP performance in mobile ad hoc networks

TCP is a transport protocol formally designed for the wired Internet and it is known to suffer from performance degradation in mobile wireless environment. In this work, we attempt to design and implement a new wireless TCP for ad hoc networks and study the performance of different approaches in order to improve the TCP throughput performance. The performance of TCP is evaluated from the protocol TCP-Bus, TCP-F and general TCP technique. For this purpose a file transfer is simulated over a wireless link using OPNET as a simulation tool. The model is developed by stages before a complete model of TCP including some of the algorithms; window size, congestion and fast retransmit is produced. The effect of various channel parameters on the performance of TCP is also discussed. The model will be evaluated in an ad hoc network where packet losses and partitions can be made. The throughput performance of TCP is measured base on the 802.11b standards of communications protocol where the transmission link is up to 11 Mbps. IEEE 802.11 is a multiple access protocol in which stations in the network must "compete" for access to the shared communications medium to transmit data. A simple modification of TCP was made and simulated, and showed that an improvement of performance is possible. The results obtained from extensive experimentation done in an ad hoc network show how the new wireless TCP with improved performance has better throughput. More research should be done to make a modification of TCP that can optimize the throughput.