Hybrid ARQ-Based Fairness Enhancement in Uplink WLAN

Per-station fairness is one of the important and challenging issues in wireless local area network based on a contention-based medium access control protocol. The unfairness problem among stations having different channel qualities is caused by the imbalance in access probability and outage probability among them. In this paper, we investigate the per-station fairness by resolving the imbalance in the above two factors through the enhanced distributed coordination function (DCF) adopting hybrid automatic repeat request (HARQ), named the DCF-H. We suggest adopting the HARQ with Chase combining as a solution for the imbalance in the outage probability on top of the loss differentiation mechanism which resolves the imbalance in the access probability. We also analyze the performance of the DCF-H by proposing a new Markov chain model and derive a closed-form expression of system throughput, delay, and outage probability. We compare the performance of the DCF-H with that of the conventional DCF protocols and find out that the DCF-H not only guarantees the near-perfect per-station fairness but also improves the whole system performance, such as throughput, delay, and outage probability.