An Efficient Backoff Scheme for IEEE 802.11e EDCF Differential Service

Abstract

Wireless LANs (WLANs) are one of the fastest growing wireless access technologies. Unfortunately, since they were developed to closely match existing wired LANs, the popular IEEE 802.11 standards have several problems in providing Quality of Service (QoS) to stations. The IEEE 802.11e standard is being developed to overcome these drawbacks. One of most important function in 802.11e is the contention-based channel access mechanism called enhanced distributed coordination function (EDCF), which provides a priority scheme by differentiating the inter-frame space and the initial window size. In this paper, we first consider the enhanced DCF access method of IEEE 802.11e. We then introduced analytical model, which can be used to calculate the traffic priority and throughput corresponding to the configuration of multiple DCF contention parameters under saturation throughput. This enhanced DCF access method differs from the standard backoff schemes in that the backoff time is not uniformly chosen in the contention window interval that results in reduced collision probability under high loads. Numerical analysis shows that saturation throughput of the proposed scheme outperform the earlier approach.