An end-to-end TCP enhanced scheme for ad hoc wireless networks

Transmission Control Protocol (TCP) is designed for reliable fixed networks, so TCP assumes that the reason of packet losses is network congestion, and accordingly triggers congestion avoidance mechanisms. Unfortunately, this is not true for wireless networks where, due to higher bit error rate and handoff, packet losses are more frequent, whereas TCP attributes these packet losses to congestion in wireless networks. This incorrect inference results in frequent TCP re-transmission time-outs and therefore the degradation in TCP performance even at light loads. Firstly, the recent developments of wireless mobile networks with TCP are introduced, and then a new TCP enhanced scheme for mobile ad hoc networks is presented. The new scheme can identify three network states, namely congestion, channel error and route change, from each other. The identification for these network states based on end-to-end measurements is mainly achieved by TCP receiver, which successively dispatches the feedback on current network states to TCP sender via the ACK packets. Consequently, the sender takes corresponding measures. Eventually, the ns-2 simulations show that in comparison with standard TCP, the new scheme greatly improves TCP performance in wireless mobile networks.