Assuring per-station fairness in multi-rate WLANs: A hybrid approach of contention window control and frame aggregation

This paper deals with fairness among stations (STAs) in multi-rate wireless local area networks (WLANs). If STAs compete for channel access according to IEEE 802.11 distributed coordination function, they have comparable opportunity of channel access, regardless of transmission rate. Accordingly, high-rate STAs achieve throughput similar to low-rate STAs, which is well known as performance anomaly. To mitigate this problem, we propose a hybrid solution combining contention window control with frame aggregation. By controlling contention window of each STA, the proposed mechanism assures higher channel access opportunity for high-rate STAs, without resulting in the unnecessary high collision probability. At the same time, it controls the frame aggregation factor based on the transmission rate of each STA, in order to tightly assure perstation fairness in terms of channel occupation time. To validate the proposed mechanism, we perform intensive simulation which confirms its outstanding performance in terms of throughput, fairness, and utilization.