Assuring user fairness in IEEE 802.11 wireless mesh network is challenging mainly for two reasons — first, the in-built unfair behavior of IEEE 802.11 contention based channel access in multi-hop forwarding, and second, the capacity degradation of mesh routers near a gateway due to the heavy traffic load. This paper studies the fundamental reason of fairness degradation in a mesh network, using a practical mesh testbed. The experimental results reveal that the flow fairness alone cannot solve this issue, because the near-gateway routers with high traffic load require more bandwidth for traffic forwarding. An improved channel access differentiation technique based on a load estimation strategy is proposed in this paper to reduce the capacity degradation of mesh routers, and to improve the fairness among end users. The proposed protocol is evaluated using results obtained from two different testbed setups. These results show that the proposed protocol improves the end-user fairness, as well as the average throughput in the network.
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