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Unformatted text preview: Mobile Networks and Applications 10, 99–113, 2005 2005 Springer Science + Business Media, Inc. Manufactured in The Netherlands. CARD: A Contact-based Architecture for Resource Discovery in Wireless Ad Hoc Networks AHMED HELMY ∗ , SAURABH GARG and NITIN NAHATA 3740 McClintock Avenue, EEB 232, Electrical Engineering Department, University of Southern California, Los Angeles, CA 90089-2562, USA PRIYATHAM PAMU Computer Science Department, University of Southern California, Los Angeles, CA 90089-2562, USA Abstract. Traditional protocols for routing in ad hoc networks attempt to obtain optimal or shortest paths, and in doing so may incur significant route discovery overhead. Such approaches may be appropriate for routing long-lived transfers where the initial cost of route discovery may be amortized over the life of the connection. For short-lived connections, however, such as resource discovery and small transfers, traditional shortest path approaches may be quite inefficient. In this paper we propose a novel architecture, CARD, for resource discovery in large-scale wireless ad hoc networks. Our mechanism is suitable for resource discovery as well as routing very small data transfers or transactions in which the cost of data transfer is much smaller than the cost of route discovery. Our architecture avoids expensive mechanisms such as global flooding and complex hierarchy formation and does not require any location information. In CARD resources within the vicinity of a node, up to a limited number of hops, are discovered using a proactive scheme. For resources beyond the vicinity, each node maintains a few distant nodes called contacts . Contacts help in creating a small world in the network and provide an efficient way to query for distant resources. Using contacts, the network view (or reachability) of the nodes increases, reducing the discovery overhead and increasing the success rate. On the other hand, increasing the number of contacts also increases control overhead. We study such trade-off in depth and present mechanisms for contact selection and maintenance that attempt to increase reachability with reduced overhead. Our schemes adapt gracefully to network dynamics and mobility using soft-state periodic mechanisms to validate and recover paths to contacts. Our simulation results show that CARD is scalable and can be configured to provide desirable performance for various network sizes. Comparisons with other schemes show overhead savings reaching over 93% (vs. flooding) and 80% (vs. bordercasting or zone routing) for high query rates in large-scale networks. Keywords: energy efficient, sensor networks, routing 1. Introduction Ad hoc networks are wireless networks composed of mobile devices with limited power and transmission range. These networks are rapidly deployable as they neither require a wired infrastructure nor centralized control. Because of the lack of fixed infrastructure, each node also acts as a relay to provide communication throughout the network. Appli-to provide communication throughout the network....
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- Spring '08
- Networking, Ad Hoc Networks, contacts, Helmy, contact selection