Title: "Quality of Service Support in IEEE 802.11 Wireless LAN"

When: March 31, 2005 1:30pm - 3:30pm

Where: Large Commons Room, 5^th Fl. IS Bldg.

Who: Wasan Pattara-Atikom

Abstract: Wireless Local Area Networks (WLANs) are gaining popularity at an unprecedented rate, at home, at work, and in public hot spot locations. As these networks become ubiquitous and an integral part of the infrastructure, they will be increasingly used for multi-media applications. The heart of the current 802.11 WLANs mechanism is the Distributed Coordination Function (DCF) which does not have any Quality of Service (QoS) support. The emergence of multimedia applications, such as the local services in WLANs hot-spots and distributions of entertainment in residential WLANs, has prompted research in QoS support for WLANs. The absence of QoS support results in applications with drastically different requirements receiving the same yet potentially unsatisfactory service. Without absolute throughput support, the performance of applications with stringent throughput requirement will not be met. Without relative throughput support, heterogeneous types of applications will be treated unfairly and their performance will be poor. Without delay constraint support, time-sensitive applications will not even be possible. The objective of this dissertation is, therefore, to develop a comprehensive and integrated solution to provide effective and efficient QoS support in WLANs in a distributed, fair, scalable, and robust manner. In this dissertation, we present a novel distributed QoS mechanism called Distributed Relative/Absolute Fair Throughput with Delay Support (DRAFT+D). DRAFT+D is designed specifically to provide integrated QoS support in IEEE 802.11 WLANs. Unlike any other distributed QoS mechanisms, DRAFT+D supports two QoS metrics (throughput and delay) with two QoS models (absolute and relative) under two fairness constrains (utilitarian and temporal fairness) in the same mechanism at the same time a fully distributed manner. DRAFT+D is also equipped safeguards against excessive traffic loads. DRAFT+D operates as a fair-queuing mechanism that controls packet transmissions (a) by using a distributed deficit round robin mechanism and (b) by modifying the way Backoff Interval are calculated for packets of different traffic classes. Fair relative throughput support is achieved by calculating BI based on the throughput requirements. Absolute throughput and delay support are achieved by allocating sufficient fair shares of bandwidth to these types of traffic. To the best of our knowledge, there are no other QoS mechanisms that can provide this level of integrated QoS support in WLAN in a fully distributed manner. We believe that the integrated solution based on distributed fair scheduling is the answer for overcoming the lack and inadequacy of the provision of QoS in WLANs. We believe that pervasive high-speed wireless data services are at the same time compelling and inevitable. It is just a question of how and when. And if we know the answer to how, then it is only a matter of time until WLANs will become aubiquitous reality.