MAC PARAMETR TUNING FOR BEST EFFORT TRAFFIC IN 802.11e CONTENTION-BASED NETWORKS

This paper deals with the problem of best effort traffic delivery in 802.11e contention-based networks. Differently from most previous paper which focus on the support of quality of service (QoS) requirements, we study the tuning of the access parameters for the best effort traffic. The contribution of this paper is threefold. First, we discuss the coexistence between legacy DCF and EDCA stations, since, for guaranteeing the backward compatibility, the best effort service class defined in EDCA should correspond to the legacy DCF. We show what configurations of the access parameters are closer to the DCF protocol, by taking into account the slightly different backoff rules defined in EDCA. Second, we explore the optimizations that can be performed by dynamically tuning the access parameters, on a per-beacon basis, in the case of homogeneous best effort sources. We propose an effective algorithm able to maximize the system throughput, by adapting the minimum contention window to the network contention level. Finally, we analyze the amount of resources available for best effort traffic in presence of QoS traffic. We show that the dynamic adaptation of the minimum contention window as a function of the channel wasted times can be a valid solution to automatically regulate the best effort offered load in the network.