Transfer-chapter-2col-4-1 - Efficient Resource Discovery in...

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Efficient Resource Discovery in Wireless AdHoc Networks: Contacts Do Help Ahmed Helmy Department of Electrical Engineering University of Southern California Abstract- The resource discovery problem poses new challenges in infrastructure-less wireless networks. Due to the highly dynamic nature of these networks and their bandwidth and energy constraints, there is a pressing need for energy-aware communication- efficient resource discovery protocols. This chapter provides an overview of several approaches to resource discovery, discussing their suitability for classes of wireless networks. The approaches discussed in this chapter include flooding-based approaches, hierarchical cluster-based and dominating set schemes, and hybrid loose hierarchy architectures. Furthermore, the chapter provides a detailed case study on the design, evaluation and analysis of an energy-efficient resource discovery protocol based on hybrid loose hierarchy and utilizing the concept of ‘contacts’. 1. Introduction Resource discovery is an essential element in the design of infrastructure-less networks. Many classes of multi- hop wireless networks, including mobile ad hoc networks (MANets) and sensor networks, are designed as infrastructure-less, unattended, rapidly-deployable networks. In these cases, each network node does not have prior knowledge of the resources available in the network. Hence, resource discovery is imperative to the design of ad hoc and sensor networks. In general, a resource can be any type of service or capability, such as nodes with high energy, processing power or storage, multiple interfaces, printing capability, or sensing capability. Also a resource may be shared information, as in file-sharing, publish-and-subscribe, storage- retrieval, and querying for sensed data. Resource discovery in wireless ad hoc and sensor networks is a challenging problem mainly due to the following reasons. First, the lack of infrastructure, where there are no well-known servers in a pre-defined network structure as in DNS. Second, the highly dynamic nature of ad hoc and sensor networks that leads to frequent changes in the network topology and resource availability and locations. Network dynamics arise mainly due to the characteristics of wireless channels, in terms of fading, interference and variability in the loss rates, in addition to possible node movement in mobile networks. Third, scarcity of energy and communication bandwidth in such networks necessitates the design of new resource discovery protocols qualitatively different from those designed for the wired Internet. In the wired Internet protocols were not designed for energy and communication constrained environments. Moreover, in many cases wireless networks may scale up to thousands of nodes rendering the discovery problem even more challenging. Service discovery may occur between the querier and
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This note was uploaded on 05/27/2011 for the course CIS 4930 taught by Professor Staff during the Spring '08 term at University of Florida.

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Transfer-chapter-2col-4-1 - Efficient Resource Discovery in...

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