Structural Unfairness in 802.11-basedWireless Mesh Networks

The use of multi-hop wireless networks based on 802.11 technology is extensive and growing, owing to their ease of deployment and low cost. However, such networks exhibit poor fairness, starving nodes that are too many hops distant from the gateway. The best current solution to this problem is source rate limiting. While effective in many topologies, this fails to completely address the fairness problem. In this paper we investigate this problem of residual unfairness in multi-hop wireless networks that use source-rate limiting. We identify the five necessary conditions for its occurrence, showing that elimination of any of these conditions is sufficient to remove the remaining unfairness. For cases where the conditions are unavoidable, we present two simple changes that can ameliorate the problem, providing on average 30% improvement for the least-rate flow.