An Adaptive Flow Control Scheme for Improving TCP Performance in Wireless Internet

Abstract

The end-to-end TCP (Transmission Control Protocol) performance is one of important issues in wireless Internet services. In this paper, a TCP aware link layer protocol, called Adaptive-TCP(A-TCP), is proposed in order to improve the performance. The key idea of the protocol is that an A-TCP agent, which is located in each base station, makes a mobile host look as if it has a wired link with the base station. In this paper, this concept is referred to a virtual host model. In order to implement it, the A-TCP agent performs three functions; Local Retransmission, Freezing Sender and A-TCP Flow Control. In this proposal, the A-TCP Flow Control is original and is also the principal factor for improving the performance in a wireless Internet. In the A-TCP Flow Control, the A-TCP agent marks the window field of acknowledgement segment with a retransmission buffer size. Therefore, the TCP congestion controls, which happen in a TCP sender, are not caused by wireless link overflow. Performance evaluations were conducted by computer simulations. The results of the evaluation show that the A-TCP can provide near optimal performance in wireless bottleneck conditions. These also suggest that the A-TCP improves performance by at least 20% compared to other TCP approaches.