Design And Performance Evaluation Of A Non-Preemptive Priority Based Access Control Scheme For IEEE 802.11 DCF Access Method

Abstract

IEEE 802.11 is a standard for wireless LANs. The basic access method in its medium access control (MAC) layer protocol is the distributed coordination function (DCF) for the ad hoc networks. It is based on the mechanism of carrier sense multiple access with collision avoidance (CSMA/CA). DCF is used to support asynchronous data transmission. However, it cannot support service discipline of integrated multimedia traffic since it does not include any priority and access control policy. With a little bad luck, a station might have to wait arbitrarily long to send a frame. In this paper, we propose a pragmatic non-preemptive priority based access control scheme for IEEE 802.11 DCF access method. Under such a scheme, modifying the CSMA/CA protocol in the contention period supports many levels of priorities such that real-time applications can be supported. Simulations are conducted to analyze the proposed scheme. The results show that it provides a good performance in IEEE 802.11 DCF environments.