Fair and Efficient TCP Access in IEEE 802.11 WLANs

We illustrate the transport layer unfairness problem in the IEEE 802.11 wireless local area networks (WLANs). We propose a novel and simple analytical model to calculate the per-flow congestion window limit that provides fair TCP access in a wired/wireless scenario where the wireless hop is an 802.11 link. The proposed analysis is unique in that it considers the effects of varying number of uplink and downlink TCP flows, varying round trip times (RTTs) of TCP connections, and the use of delayed TCP acknowledgment (ACK) mechanism. The comparison with simulation results validates the accuracy of the analytical estimations on the congestion window limit. When the TCP connections use the congestion window limits calculated from the proposed model, not only fair access can be provisioned, but also the channel can be utilized efficiently in a wide range of scenarios.