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Title page for ETD etd-08082007-134114

Type of Document Dissertation
Author Kusy, Branislav
URN etd-08082007-134114
Title Spatiotemporal Coordination in Wireless Sensor Networks
Degree PhD
Department Computer Science
Advisory Committee
Advisor Name Title
Janos Sztipanovits Committee Chair
Akos Ledeczi Committee Co-Chair
Juan Xue Committee Member
Miklos Maroti Committee Member
Xenofon Koutsoukos Committee Member
  • Doppler effect
  • radio interference
  • tracking
  • localization
  • Kalman filter
  • ranging
  • Sensor Networks
  • synchronization
  • time
  • proactive
  • post-facto
  • low duty cycle
  • experimental evaluation
  • space
Date of Defense 2007-08-01
Availability unrestricted
Large-scale networks of low-power, wireless devices integrated with sensors and actuators have

emerged as a new platform that promises to seamlessly integrate computational devices with our

environment. Information about various phenomena occurring both in nature and human created

environments can be gathered at a fine scale, unobtrusively, remotely, and in a cost-effective

manner. Such information can be used to control and manage production facilities, predict and asses

natural disasters, or obtain better understanding of animal species or natural processes.

The notion of time and space is fundamental in the context of these wireless sensor networks

(WSNs): data is typically gathered at different physical locations and at a different time, thus

the interpretation of the data is contingent upon the existence of inter-node synchronization of

time and location coordinates. In this thesis, we address both temporal and spatial coordination of


We argue that structuring time synchronization protocols into layers and standardizing interfaces

of these layers improve adaptability, reusability, and portability of the protocols and help to

decrease the complexity and increase the efficiency of their implementation. In our approach, time

synchronization protocols are structured in three layers which communicate through well defined

application programming interfaces (APIs). Further, we provide implementation, performance

analysis, and quantitative comparison of a number of time synchronization services which will help

developers to identify the time synchronization needs of their WSN applications.

Despite the considerable research effort invested in the area of node localization, a robust sensor

localization is still an open problem today when applied to real world problems. Existing

techniques have limited range and accuracy, require extensive calibration, or need extra hardware

that adds to the cost and size of the platform. We propose a novel radio interferometric ranging

technique that utilizes two transmitters emitting radio signals at almost the same frequencies. The

relative distances between the nodes are estimated by measuring the relative phase offset of the

generated interference signal at two receivers. We implement interferometric ranging on a low-cost

low-power off-the-shelf hardware and demonstrate that both high accuracy and large range can be

achieved simultaneously. Furthermore, we present the results of localization and real-time tracking

experiments deployed in rural and urban environments, demonstrating that our techniques allow for

economical deployments and outperform existing localization services.

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