Air fair scheduling for multimedia transmission over multi-ratewireless LANs

Abstract

As wireless local area networks (WLANs) are becoming ubiquitous, there is an increasing demand for their application in multimedia transmission for both professional and personal uses. Multimedia applications are delay-sensitive and require specific Quality of Service (QoS) support. Scheduling is very crucial to support multimedia transmissions with performance guarantees in the IEEE 802.11e WLAN. Most of the work on scheduling are based on bandwidth sharing techniques which are not suitable for wireless systems where the physical transmission rate varies as a function of distance or signal to noise ratio as in IEEE 802.11/GPRS/3G networks. In such a network, we show that the widelyadopted concept of throughput fairness forces low-transmission rate stations to overuse air time, thus causing significant unfairness in air time usage among the different stations. In this chapter, we first present a scheme called Air Fair Scheduling (AFS), which (1) always guarantees fairness in terms of received air time, regardless of the underlying stations' transmission rates; (2) keeps service for individual stations unaffected by other stations' transmission rate fluctuations or transmission errors; and (3) also achieves a higher overall system throughput than generalized processor sharing (GPS). We provide an algorithm for AFS implementation in IEEE 802.11a/e system and show how the performance is enhanced through analysis and experiments. © 2006 Springer.