TCP analysis over wireless mobile ad hoc networks

Reliable transport protocols like TCP are fine-tuned to perform well in wired networks with stationary nodes. But, when used in wireless networks, these protocols give poor performance. The decrease in the performance is due to the violation of the main assumption of the TCP, which says that any loss of the packet is due to the congestion in the network only. There is a high probability in mobile wireless networks that a packet loss can occur due to the transmission errors or due to the unavailability of the route. But, TCP reduces the congestion window in response, causing unnecessary degradation in throughput. This problem is further compounded in a wireless mobile ad hoc network where there is no basic infrastructure binding the mobile nodes and frequency of route failures is high. So, performance of TCP in mobile ad hoc networks can be extremely poor due to frequent route changes, high bit error rates and network partitions. We have analyzed the performance of TCP over a highly mobile ad hoc network. We have studied the relative performance of three different variants of TCP - TCP Reno, TCP SACK and TCP Vegas. The relative performance of two on-demand ad hoc routing protocols - AODV and DSR with respect to transport protocols is also observed. Our studies show that the performance of TCP is variable and dependent on the mobility patterns of the mobile nodes.