Contention window adaptation to ensure airtime consumption fairness in multirate Wi-Fi networks

Abstract

In the paper we address a problem of throughput unfairness inherent in the very nature of multirate Wi-Fi networks employing CSMA/CA mechanism. This unfairness exhibits itself through the fact that slow clients consume more airtime to transfer a given amount of data, leaving less airtime for fast clients. The paper introduces analytical models allowing to estimate a fair contention window (CW) size to be used by each station depending on a ratio between station's data rates. Finally, we propose a lightweight distributed algorithm that enables stations to dynamically adapt their CW so that a suboptimal airtime distribution between them is ensured. It prevents network throughput from being dramatically degraded when a slow station is connected to the network.