An extension of the TCP flow control algorithm for wireless networks

Reliable transport protocols such as the Transmission Control Protocol (TCP) are tuned to perform well in traditional wireline networks where packet losses occur mostly because of congestion. However, networks with wireless and lossy links also suffer from significant packet losses due to bit errors and handoffs. TCP responds to all the packet losses by invoking congestion control and avoidance algorithms and this results in degraded end-to-end performance in wireless and lossy systems. In this paper we propose a simple strategy to determine the cause of packet drops in a network running the TCP protocol. Our method is based on observing the slow start threshold value and the number of packets successfully transmitted between two consecutive drops. We then show that additive increase and multiplicative decrease algorithm of TCP results in unfair allocation of bandwidth to wireless connections. Thus, it needs to be modified to take into account the wireless drops. We present the performance of one such strategy which takes corrective action once a drop is identified as a wireless drop.