TCP window control for QoS improvement based on channel occupancy information over wireless LAN

TCP has been a congestion control method in the Internet. However, since TCP is not able to directly measure the network status from the end nodes, the TCP window control gradually increases the congestion window size until congestion occurs. This control gets network bandwidth aggressively and affects communication of all stations (STAs) which belong to the same access point of IEEE 802.11 standards. Especially, the communication quality for real-time applications such as video streaming becomes worse. To improve this problem, we have proposed a TCP window control method with adjusting the congestion window size for available bandwidth of the access point. TCP window size is adequately controlled by measuring the channel occupancy of each STA. The channel status information is passed to the TCP window control function via a cross layer control mechanism. We have developed a testbed and shown the effectiveness of our method by empirical evaluations.