Overview of Techniques for Improving QoS of TCP over Wireless Links

Internet protocol architecture is totally based on layered approach. However, layer independence may lead to nonoptimal performance in wireless systems. In fact, many assumptions for the wired networks are not applicable to wireless environments. For example, all the losses in the wireless channel are not due to congestion, where packets can be lost due to the link failure. In this paper, we compare several schemes designed to improve the performance of TCP in such networks. These schemes are classified into three broad categories: end-to-end protocols, where the sender is aware of the wireless link, link layer protocols, that provide local reliability, and split-connection protocols, which break the end-to-end connection into two parts at the base station. Our study shows that a reliable link-layer protocol with some knowledge of TCP provides very good performance. Furthermore, it is possible to achieve good performance for hybrid network without splitting the wired and wireless connection at the base station.