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University of Cambridge Computer Laboratory
Friday June 30th, 2006 - 3pm
Computer Laboratory > Research > Systems Research Group > NetOS > Seminars > Friday June 30th, 2006 - 3pm

Using Smart Triggers for Improved User Performance in 802.11 Wireless Networks

Konstantina Papagiannaki

The handoff algorithms in the current generation of 802.11 networks are primarily reactive in nature, because they wait until the link quality degrades substantially to trigger a handoff. They further rely on instantaneous signal strength measurements when choosing the best AP. This approach leads to handoff delays on the order of 1-2 seconds that are unacceptable for delay sensitive applications such as VoIP. We propose a fundamentally new approach to handoffs that is based on continuous monitoring of wireless links. In our approach, a client measures the beacon strengths of all the APs operating on the current, and the overlapping channels, and makes its handoff decisions based on the long-term, and short-term trends in these signals. We show through experiments in a campus wireless network that our proposed algorithms result in more than 50% reduction in average handoff delays, while having the potential to improve overall user performance. Our algorithms have been implemented in today's hardware, and unlike other proposed roaming algorithms in the literature, need no infrastructure support.

Joint work with Vivek Mhatre. This paper appeared in ACM Mobisys 2006. The success on managing large networks and the services running on them is closely related to the quality of the operational control of the net and the feedback from the customers. As these networks get complex and the services ubiquitous, there is a need for more flexible, dynamic and abstract ways to measure the quality of the services provided to customers. In this talk we introduce the idea of using ontologies to structure the management information in such a way that it would provide some key factors we understand will be of importance for managing services in the future: sharing and collaboration between providers (and users); high level common specifications; on-the-fly mapping of policies; context awareness; etc. We will spend some time demonstrating the potential use of ontologies on a similar problem: security management. The creation of two ontologies, Security Incident and Vulnerabilities, with the definition of classes, relationships and the possibilities of data correlations, will be described.