Preventing the performance anomaly of IEEE 802.11 networks with a distributed channel-aware scheduler

In previous works we have introduced the DTT (Deficit Transmission Time) scheduler, an algorithm to be run at the Access Point to contrast the performance anomaly affecting IEEE 802.11 based networks. DTT has indeed proved to be very effective, as it is able to guarantee proportional fairness and isolation to downlink flows. Yet, due to its centralized nature, it can only put in place a suboptimal solution, as the uplink flows are still uncontrolled We have therefore extended the idea of DTT to a distributed version of the scheduler, called Distributed DTT, or (DT)². The paper, beyond describing this new algorithm, presents the results of an extensive set of simulations. These show that (DT)² is able to defeat the performance anomaly for uplink flows, thus complementing its ancestor perfectly. A useful side effect is the reduction of the bottleneck effect, that allows more fairness between uplink and downlink directions. We show that these achievements are crucial in supporting the emerging Voice Over WLAN services.