Interference Mitigation Through Power Control in High Density 802.11 WLANs

The low cost and the ease of deployment of WiFi devices, as well as the need to support high bandwidth applications over 802.11 WLANs has led to the emergence of high density 802.11 networks in urban areas and enterprises. High density wireless networks, by design, face significant challenges due to increased interference resulting from the close proximity of co-channel cells. We demonstrate that power control can be used to mitigate interference in such an environment. It is well-known that variable transmit powers result in asymmetric links in the network, and can potentially lead to throughput starvation of some nodes. We first show that in order to perform starvation-free power control in 802.11 networks, a cross-layer approach is required, whereby the transmit powers and the carrier sensing parameter of the MAC layer of the nodes should be jointly tuned. We then propose a framework that determines optimum settings for these parameters with the objective of maximizing the network-wide throughput for elastic traffic. Within this framework, we devise a distributed power control algorithm that uses a Gibbs sampler. OPNET simulations and experiments over a proof of concept testbed demonstrate that in a dense network the proposed power control algorithm yields significant improvement in client throughput.