QoS Provisioning in IEEE 802.11 WLAN

Abstract

IEEE 802.11 Wireless LAN (WLAN) is fast rising as a prevailing solution for the broadband wireless networking. However, today's 802.11 WLANs cannot provide any quality-of-service (QoS) guarantee because of its contention-based channel access nature of the mandatory distributed coordination function (DCF). Recently, the needs for real-time services such as Voice over IP (VoIP) and audio/video (AV) streaming over WLANs have been increasing drastically. Accordingly, remarkable research efforts have been carried out to enhance the legacy 802.11 Medium Access Control (MAC) for QoS support. Moreover, the emerging IEEE 802.11e, which is an amendment of the existing 802.11 MAC is expected to provide QoS. In this chapter, we focus only on the schemes based on contention-based channel access. After a short overview of research trends on QoS provisioning in the 802.11 WLAN, we introduce a simple software upgrade-based solution, called a dual-queue scheme, and the emerging IEEE 802.11e standard to support QoS. The former can be considered a short- and mid-term solution to provide a limited QoS to real-time services, and the latter can be considered a long-term solution, which supports QoS at the MAC level. Finally, we compare three schemes, namely, legacy DCF, dual queue, and 802.11e EDCA schemes via simulations.