Delay Analysis of IEEE 802.11e EDCA Under Unsaturated Conditions

With the successful development of IEEE 802.11 based wireless LAN(WLAN), applications with QoS requirements are asked to be provided in WLANs. Because of their delay restrictions, realtime applications should work under unsaturated conditions. In this paper, firstly, traffic models for different kinds of applications are proposed to convert the unsaturated system into an equivalent saturated system and calculated out the queueing delay in the sender buffer; then, a new analysis model is presented to analyze the backoff delay and packet loss rate of all kinds of applications under the IEEE 802.11e enhanced distributed channel access (EDCA), this model well embodies the function of the arbitration inter frame space(AIFS) and other EDCA parameters; finally, access delay can be get from the backoff delay and queueing delay. Practical scenarios of voice over IP(VoIP) and data combined system are simulated. Simulation results show the accuracy and efficiency of our model under unsaturated conditions.