Enhanced DCF of IEEE 802.11e to support QoS

We introduce the emerging IEEE 802.11e standard to support quality of service at medium access control level. One of the most important functions 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. We propose an analytical model to evaluate the EDCF priority scheme. Saturation throughput and saturation delay are derived analytically. Simulations are also conducted to validate analytical results. Our study shows that differentiating the initial window size is better than differentiating the inter-frame space in terms of total throughput and delay.