Achieving per-station fairness in IEEE 802.11 wireless LANs

In this paper, we address the issue of per-station fairness in IEEE 802.11-based wireless local area networks (WLANs). Although the IEEE 802.11 Distributed Coordination Function (DCF) has been designed to provide a fair channel access for all competing stations, it does not guarantee fairness between uplink and downlink flows in infrastructure mode WLANs. In the literature, several solutions have been proposed, where they give a higher channel access priority to an access point (AP) in order to avoid the starvation of downlink flows. However, we found that existing solutions cannot guarantee per-station fairness when uplink and downlink flows coexist in a station. In this paper, we propose a new MAC protocol for IEEE 802.11 WLANs, which aims at providing a fair medium access for all stations regardless of the direction of flows. In the proposed protocol, stations are classified into four states according to their traffic patterns, and they access the medium in different ways according to their states. The proposed protocol is fully backward compatible with the IEEE 802.11 standard and it does not include any complex scheduling algorithm. We evaluated the performance of the proposed protocol via extensive simulations and experiments in a real test-bed. Compared to existing work, the proposed protocol shows improved fairness performance in resource sharing among WLAN stations.