Analysis of the Total Delay of IEEE 802.11e EDCA and 802.11 DCF

A packet sent from an upper-layer protocol or application over IEEE 802.11 [1] will first be placed in a transmission queue. The packet delay caused by waiting here is referred to as the queueing delay. When the packet reaches the head of the queue it will start contending for channel access until it is successfully transmitted over the medium (or finally dropped). The delay associated with the medium access is referred to as the MAC delay. The majority of analytical work on the delay performance of IEEE 802.11 focuses on predicting only the mean MAC delay, although higher layer applications and protocols are interested in the total performance of the MAC layer. The main contribution of this paper opposed to other works is that it provides analytical predictions of the total delay, which also includes the queueing delay. The analyses presented apply to the priority schemes of the Enhanced Distributed Channel Access (EDCA) mechanism of the IEEE 802.11e standard [2]. However, by using an appropriate parameter setting, the results presented are also applicable to the legacy 802.11 Distributed Coordination Function (DCF) [1]. The model predictions are calculated numerically and validated against simulation results.