Date of Award

4-2006

Degree Name

Doctor of Philosophy

Department

Computer Science

First Advisor

Dr. Ajay Gupta

Second Advisor

Dr. Mohsen Guizani

Third Advisor

Dr. Zijiang Yang

Fourth Advisor

Dr. Song Ci

Abstract

With the proliferation of wireless sensor networks, providing location-aware technology and services to new applications have become important for developers. Localization is the problem of determining the positions of nodes in an ad hoc network. With the constrained resources of network sensors, providing robust localization services remains a fundamental research challenge facing the entire sensor network development community.

The initial localization problem that we addressed was to design and develop a working system that could locate equipment, such as a laptop or video projector. Ferret, the localization system developed, uses two different ranging techniques to help locate an object to within one meter.

Our next goal was to identify the locations of all nodes in a sensor network given the locations of a small subset of nodes. The system we developed, LESS or Localization using Evolution Strategies in Sensomets, provides substantial energy savings over existing techniques while providing comparable accuracy.

We then introduce an efficient location discovery algorithm that bounds the localization error. Our algorithm, based on finding the smallest circle enclosing the intersection of n disks, runs in O(n ) time. We extend our work to the problem of finding the smallest disk that includes the set of points common to n disks and excluded from the interiors of m other disks.

Many localization techniques say that a node can either be localized or it cannot. We present a location discovery algorithm that provides, for every node in the network, a position estimate, as well as an associated error bound and confidence level. We provide a versatile framework that allows users to perform localization queries based on the required accuracy and certainty.

Ensuring coverage of a wireless sensor network is critical in many applications. Most schemes that analyze and implement coverage assume that sensor locations are known. For large sensor networks, errors occur when estimating node positions. Based on the errors that arise from the localization process, we present coverage algorithms that associate a confidence level with the coverage. We introduce a system that handles user coverage queries based on the coverage and certainty a situation requires.

Access Setting

Dissertation-Open Access

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