Browsing by Author "Noh, Sam H."
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Item Information Dynamics Applied to Link-State Routing(2002-01-31) Eom, Hyeonsang; Agrawala, Ashok K.; Noh, Sam H.; Shankar, A. UdayaInformation Dynamics is an information-centric framework that provides a sufficient understanding of the characteristics of information used in systems for better system design and implementation. In this paper, we describe how to improve link-state routing based on this framework. Link-state routing protocols such as OSPF (Open Shortest Path First) are currently used in many networks. In link-state routing, routes are determined based on link-delay estimates, which are periodically flooded throughout the network. This flooding of link-delay estimates is done without considering the relevance of these estimates to routing quality, i.e. without taking into account the usefulness of the link-delay information. We have developed a new approach that improves link-state routing by estimating future link delays and flooding these estimates only to the extent that they are relevant. This means that we consider the dynamics of the link-delay information and its usefulness. Simulation studies suggest that our approach can lead to significant reductions in routing traffic with noticeable improvements of routing quality in high-load conditions, demonstrating the effectiveness of the framework. We plan to further investigate the conditions where our information-dynamics approach is better than the standard approach. (Also UMIACS-TR-2001-75)Item A Probabilistic Clustering-Based Indoor Location Determination System(2002-04-04) Youssef, Moustafa A.; Agrawala, Ashok; Shankar, A. Udaya; Noh, Sam H.We present an indoor location determination system based on signal strength probability distributions for tackling the noisy wireless channel and clustering to reduce computation requirements. We provide two implementation techniques, namely, Joint Clustering and Incremental Triangulation and describe their tradeoffs in terms of location determination accuracy and computation requirement. Both techniques have been incorporated in two implemented context-aware systems: User Positioning System and the Rover System, both running on Compaq iPAQ Pocket PC's with Familiar distribution of Linux for PDA's. The results obtained show that both techniques give the user location with over 90% accuracy to within 7 feet with very low computation requirements, hence enabling a set of context-aware applications. Also UMIACS-TR-2002-30