An 802.11 Based MAC Protocol for Providing QoS to Real Time Applications

IEEE 802.11 based wireless LANs (WLAN) are ubiquitous nowadays. Running real time voice and video applications over LANs is becoming common place. These applications require QoS in terms of delay, throughput etc. But 802.11 does not have inherent QoS support. Since 802.11 has a large installation base providing QoS in 802.11 WLANs is an important issue. In this paper, we propose a MAC protocol based on 802.11 which can provide QoS to real time applications. The MAC assigns different contention window to two priority classes to provide service differentiation. When collision occurs, contention window is increased in a linear fashion and the new contention windows for high and low priority traffic become non-contiguous. This unique method of contention window management provides better relative performance between the two classes. We present an analytical model to show that high priority class gets better service and report our simulation results to compare performance of our protocol with 802.11e. Further, our protocol can be implemented with very minimal change in 802.11 code.