Evaluation of Quality of Service Schemes for IEEE 802.11 Wireless LANs

This paper evaluates four mechanisms for providing service differentiation in IEEE 802.11 wireless LANs, the Point Coordinator Function (PCF) of IEEE 802.11, the Enhanced Distributed Coordinator Function (EDCF) of the proposed IEEE 802.11e extension to IEEE 802.11, Distributed Fair Scheduling (DFS), and Blackburst using the ns-2 simulator. The metrics used in the evaluation are throughput, medium utilization, collision rate, average access delay, and delay distribution for a variable load of real time and background traffic. PCF performance is comparably low, while EDCF performs much better. The best performance is achieved by Blackburst. DFS provides relative differentiation and consequently avoids starvation of low priority traffic.