The emerging IEEE 802.11e standard is expected to provide service differentiation and resource allocation for realtime traffic. To support the transmission of voice and multimedia data with performance guarantees, it is crucial to design efficient algorithms for admission control and resource allocation (particularly under heavy load), and several methods have been proposed to date. However, most of these proposed methods may not be efficient, because they assign channel access parameters

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... ss parameters (CAPs) according to the access category into which a flow is mapped rather than the absolute quality-of-service (QoS) requirements of the flow. Using simulations, we highlight the shortcomings of current admission control methods, and accordingly, we propose a flow-based service differentiation mechanism. We introduce the proper "per-flow" selection of CAPs based on the QoS requirements of traffic flows. Furthermore, the new flow-based admission can control and adjust CAPs with the channel condition variations. We validate our reasoning through extensive simulations and a thorough comparison with other schemes. Index Terms-Admission control, IEEE 802.11e, wireless networks. 0018-9545/$25.00 She is currently an Associate Professor with the Department of Electrical and Computer Engineering, Concordia University. Prior to joining the faculty at Concordia University, she was a Protocol Design Engineer and a Software Engineer in industry, where she was involved in providing specifications and design issues for TCP/IP and Voice-over-IP support and in the software development life cycle of real-time embedded software. Her current research interests are the various aspects of real-time and multimedia communication over the Internet and over access networks. Yi Liu (S'05) received the B.Eng. degree from Nanjing University of Posts and Technology, Nanjing, China, and the M.E.