A Two-Tiered Time and Throughput Fair Scheduler for Multi-Rate WLANs

Low throughput due to unfairness is a key problem in multi-rate wireless local area networks. To promote fairness and hence throughput, T -Fair groups flows according to their average data rate, provides each group fair time allocations and ensures throughput fairness for flows in each group. Since each group is allocated transmission times fairly, T -Fair isolates high and low rate groups and prevents system capacity from being degraded by low rate flows. We have derived T -Fair’s performance bounds analytically and investigated its performance using the ns-2 simulator in various scenarios with a mix of high and low rate flows. Our results show that T -Fair is effective in isolating and providing proportional throughput fairness to flows.