Efficient QoS Differentiation in Crowded Wireless LANs

The IEEE 802.11e standard has introduced specifications for service differentiation among different classes of data by specifying four service classes and a new contention resolution mechanism called EDCA. However, while the protocol shows a better performance for higher priority data such as voice and video, the performance is seen to drop drastically at high loads. In this paper, we explore the effectiveness of a multi-stage contention scheme for providing QoS differentiation among four different service classes, as specified by EDCA. From our analysis, we observe that the multi-stage with prioritization that we propose gives a much better performance than EDCA for higher priority data. Moreover, its good performance even at high network loads shows that this design is much more scalable.