E-TCP: Enhanced TCP for IEEE802.11e Mobile Ad Hoc Networks

TCP, the facto standard used in today´s Internet, has been found to perform poorly in Mobile Ad Hoc Networks (MANETs). This is exacerbated by contention with increasing UDP-based high priority multimedia traffic and the class differentiation introduced in current QoS protocols, which results into TCP starvation and increased spurious timeouts. In this paper, we propose a cross-layer TCP enhancement (E-TCP) that makes use of TCP bidirectionality to avoid TCP traffic starvation and spurious retransmissions in presence of high priority traffic. E-TCP is based on prioritizing TCP acknowledgement packets and on adjusting TCP retransmission timer based on the medium contention. Our simulation results reveal considerable improvements in TCP performance in terms of gooput, delay and retransmission efficiency, while the better channel utilization results into even better high priority traffic performance.