Enhancing fairness and throughput of TCP in heterogeneous wireless networks

TCP exhibits inherent unfairness towards connections with long round-trip times and connections that have to traverse multiple congested routers. We have previously proposed a TCP Bandwidth Allocation (TBA) algorithm to solve this problem and proved its effectiveness in wireline networks. In this paper, we apply the TBA algorithm to improve TCP fairness over heterogeneous wireless networks with combined wireless and wireline links. In such networks, TCP suffers significant throughput degradations due to its window being frequently shut down, not in response to congestion, but by packet losses due to transmission errors over wireless links. We propose to apply Wireless Explicit Congestion Notification (WECN), a version of ECN enhanced for wireless networks, to decouple congestion control and loss recovery. Further enhancement is also incorporated to smooth traffic bursts. Simulation results show that not only can the combined TBA/WECN mechanism improve TCP fairness, but it can maintain good throughput performance in the presence of wireless losses as well. 1