Location-based routing significantly reduces routing overheads in ad hoc networks by utilizing position information of mobile nodes in making forwarding decisions. Location service is therefore critical to location-based routing, the scalability of which hinges largely on the location query and update overheads of such service. Although several location service schemes have been proposed, most of them focus only on one or two aspects of the scalability in their performance evaluation, and a comprehensive comparative study is missing. In this paper, we first explore the design space of location service for location-based ad hoc routing and discuss the tradeoffs involved in various design choices. We then propose HIGH-GRADE, a new location service scheme that employs a multilevel hierarchical location server structure and a multi-grained location information organization. We develop a uniform theoretical framework to analyze HIGH-GRADE and four other existing schemes in terms of three metrics: location maintenance cost, location query cost, and storage requirement cost. With both theoretical analysis and simulation experiments, we show that HIGH-GRADE demonstrates superior scalability, especially when a localized data traffic pattern is assumed, in which case all the three scalability metrics are bound byO(v log N).
Yu, Yinzhe; Lu, Guor-Huar; Zhang, Zhi-Li.
Enhancing location service scalability with HIGH-GRADE.
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