Achieving maximum throughput and service differentiation by enhancing the IEEE 802.11 MAC protocol

To satisfy various needs and priorities of different users and applications, Wireless LANs are currently evolving to support service differentiation. Work is in progress to define a standard enhanced version of the IEEE 802.11 Distributed Coordination Function (DCF), capable of supporting QoS for multimedia traffic at the MAC layer. This paper focuses onto one of the building blocks of this enhancement, i.e., differentiating the minimum contention window size according to the priority of different traffic categories. The novel contribution is the analysis of the optimal operation point where the maximum throughput can be achieved. The second contribution is the proposal of simple adaptive schemes which can lead the system to operate under the optimal operation point and, at the same time, achieve the target service differentiation between different traffic flows. Results obtained in the paper are relevant for both theoretical research and implementations of real systems.