IMPROVING TCP PERFORMANCE OVER WIRELESS NETWORKS

Abstract

The anticipated emergence of mobile computing and wireless data communication networks like GPRS, depends on the ability to support data applications over heterogeneous networks comprising both wireless and wire-line links. Many existing applications (including file transfers and web transactions) are based on TCP, the Internet end-to-end data transport protocol. TCP has been designed to work well in networks made up exclusively of wired links. However, TCP performance gets severely affected when used in wireless links, where the channel is typically characterized by random errors due to fading and shadowing. In this thesis we consider the wireless link with Rayleigh fading and ARQ based link layer recovery. TCP's congestion control and avoidance mechanisms to handle packet losses in wired networks do not work well in wireless system. This causes severe throughput degradation. Researchers have been proposed many schemes to improve TCP performance over such lossy wireless networks, This thesis gives an overview of all these schemes and detailed simulation study of two of these schemes namely, Link Level Error Control and Explicit Loss Notification (ELN). It has been shown that Link Level Error Control scheme improves TCP Throughput better than ELN scheme. We proposed a new scheme, which further improves TCP throughput with link level error control. The software is written in C++, and runs under Linux/Unix environment.