Improvement of TCP Throughput in Wireless Networks with High Delay Round-Trip Time

Highly variable round-trip times (RTTs) in wireless networks can induce spurious timeouts, thus unnecessarily degrading throughput for the Transmission Control Protocol (TCP). In this paper, we propose and study two effective ways to improve TCP throughput in wireless networks. The first technique is to select a retransmission timeout (RTO) threshold higher than that in the de facto standard. Simulation reveals that the proposed method reduces timeouts and provides a relative throughput gain up to 13.7% based on RTT measurements in a commercial 3G network and in a simulated network environment. The second technique is an appropriate use of selective repeat (SR) and go-back-N (GBN) as retransmission policies upon packet timeout. We find that when RTTs have reasonable temporal correlation and packets can arrive out-of-order at the receiver, GBN can improve throughput over the SR policy. Specifically, based on the RTT measurements in the 3G network, our results show that GBN provides a 12% throughput gain over the SR policy.