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With the provisioning of high-speed wireless LAN (WLAN) environments, multimedia services (e.g., VoIP and video-conference) with different QoS requirements will be available in next generation WLANs. Multimedia services could be categorized into multiple traffic classes and different priorities will be applied to access the wireless medium. The IEEE 802.11 working group has been developing a new generation distributed access protocol, called enhanced distributed channel access (EDCA), to support service differentiation in the 802.11 MAC layer. Service differentiation is achieved by assigning different values of EDCA access parameters (i.e., minimum contention window, maximum contention window, and arbitration interframe space) to different traffic classes. To investigate the system performance under various network conditions, it is helpful to have a theoretical model for EDCA. In this paper, we introduce an analytical model for EDCA so that the saturation bandwidth can be estimated by closed-form formulas for each traffic class. We use ns-2 simulator to validate the analytical model. Some numerical results are provided to evaluate the performance of EDCA. The numerical results demonstrate the corresponding effects for tuning different EDCA access parameters.

Keywords: analytical model, IEEE 802.11, medium access control, performance evaluation, wireless local area networks

Retrieve PDF document (200801_14.pdf)

Received March 2, 2006; revised June 13, 2006; accepted September 25, 2006.
Communicated by Sy-Yen Kuo.