Achieving weighted fairness in WLAN mesh networks: An analytical model

Multi-hop WLAN mesh networks employing the enhanced distributed channel access (EDCA) scheme as the medium access control protocol have been shown to suffer from serious throughput unfairness among competing flows. Indeed, some flows can even capture the whole channel bandwidth while other flows get starved. In this paper, we focus on achieving weighted fairness for differential services in WLAN mesh networks. We first introduce the concepts of the instantaneous collision zone and the persistent collision zone of receivers in multi-hop networks. Then we suggest that collisions induced by the hidden jammers located in the persistent collision zone of receivers are the primary causes for the throughput unfairness. We further develop a three-dimensional Markov chain model to determine how to precisely tune the backoff persistence factors to achieve the weighted fairness for flows with diverse quality of service (QoS) demands. In this model, we put forward the pseudo states to distinguish the different backoff procedures induced by the RTS collisions and the data collisions. Through analytical modeling, we get the proper backoff persistence factors to achieve a predefined weighted fairness goal. Finally, we validate the accuracy of our model by comparing the analytical results with that obtained by means of simulations.