Adjusting TCP window flow control based on channel occupancy information of IEEE 802.11 systems

TCP has been used as the main method of congestion control in the Internet. In the TCP window control, the window size is gradually increased until congestion occurs. This method of control acquires network bandwidth aggressively and affects other stations which communicate via the same access point using IEEE 802.11 standards. To improve this problem, we propose a congestion window control method which involves adjusting the window size without affecting the communication of the other stations. The congestion window size is adequately controlled by measuring the channel occupancy of each station. The channel occupancy is estimated by measuring the Network Allocation Vector (NAV) in each station. The channel status information is passed to the TCP congestion control function via a cross-layer control mechanism. Then, the TCP congestion window and advertised window are adjusted to take account of the channel occupancy. We have developed a testbed and shown the effectiveness of our method by empirical evaluations.