IMPROVING TCP THROUGHPUT AND FAIRNESS OVER MULTI-RATE IEEE 802.11 WIRELESS LANS

As the increase of wireless network applications based on TCP/IP, many researchers have been trying to develop TCP according to wireless environments. However, most of the proposed schemes do not consider the multi-rate capability of WLANs. In this paper, through experiments in 802.11b WLAN based multi-rate environments having data rates of 2Mbps, 5Mbps, and 11Mbps, we show that total throughput of TCP is degraded when multiple flows with different transmission rates go through a base station and analyze the reason in details. Then, we propose a rate adaptive flow control scheme in which rate-proportional buffer allocation is performed at the BS to increase the total network throughput as well as to reduce the sensitivity of TCP throughput to the available BS buffer space by guaranteeing the temporal fairness of each flow. The performance is evaluated by simulation using ns2, and the results show that the proposed scheme increases the total network throughput and guarantee temporal fairness among concurrent multiple flows.X112sciescopu