Scheduling of real-time and nonreal-time traffics in IEEE 802.11 wireless LANs

Abstract

MAC (Media Access Control) Protocol in IEEE 802.11 Wireless LAN standard supports two types of services, synchronous and asynchronous. Synchronous type of traffic i.e. real-time traffic is served by Point Coordination Function (PCF) that implements polling access method. Asynchronous type of traffic i.e. nonreal-time traffic is provided by Distributed Coordination Function (DCF) based on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol. Since real-time traffic is sensitive to delay, and nonreal-time traffic to error and throughput, proper traffic scheduling algorithm needs to be designed. But it is known that the standard IEEE 802.11 scheme is insufficient to serve real-time traffic. And there are a few parameters that influence on performance of system, but not defined. The purpose of this paper is to design these parameters and to propose a traffic scheduling and admission control algorithm for wireless LAN to satisfy the QoS requirements of real-time traffic while guaranteeing minimum throughput for nonreal-time traffic. We conduct performance evaluation and present numerical results to verify that the proposed scheme attains good performance through simulations. Proper system capacity for QoS guarantee is presented with simulation under realistic assumptions. It is shown that the system performance is decline without admission control, and EDD policy improve the performance in large.