Performance Evaluation of Quality of Service in IEEE 802.11e Wireless LANs

There have been many performance studies on the original IEEE 802.11 distributed coordinated function using both simulation and analytical methods. However, the recent IEEE 802.11e standard has not yet been investigated extensively. This paper proposes an accurate analytical model for the enhanced distributed channel access (EDCA), which is the core protocol of 802.11e. The model captures the operations of service differentiation using different contention window (CW) sizes, arbitrary interframe space (AIFS), and transmission opportunity (TXOP) limits in EDCA. Using this model, we derive throughput performance of EDCA access categories differentiated through the above mechanisms. The throughput and collision probability derived by our model are validated by simulation results, which show close agreements with the analytical results. Our model provides a useful tool for evaluating the impact of different parameters on the performance of EDCA service differentiation.