Enhancing TCP performance over wireless network with variable segment size

Abstract

In wireless network, unlike wired network, non-congestion loss due to data corruption by channel noise is not negligible. As TCP does not distinguish loss types, congestion loss and non-congestion loss, it applies congestion control to non-congestion loss and it reduces the performance of TCP. Many approaches such as split-connection and end-to-end schemes are suggested to solve this problem of TCP over wireless network. They distinguishes loss types and apply congestion control to congestion loss only. However, they do nothing when a non-congestion loss occurs. This thesis proposes a new transport protocol for wireless networks, Variable Segment size Transmission Control Protocol (VS-TCP), that has reaction mechanism for a non-congestion loss. As the number of non-congestion loss in a unit time indicates the degree of bit error rate of wireless link, our proposal changes segment size of TCP during a connection according to non-congestion loss rate. If loss is frequent, it decreases segment size to reduce the retransmission overhead and packet corruption probability and, reversely, if loss is rare, it enlarges segment to reduce the header overhead. Our simulation shows that the segment variation mechanism of VS-TCP achieves a substantial performance enhancement.