Time-based Location Techniques Using Inexpensive, Unsynchronized Clocks in Wireless Networks

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dc.contributor.advisorAgrawala, Ashok Ken_US
dc.contributor.authorMah, Matthew Yew Munen_US
dc.contributor.departmentComputer Scienceen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.date.accessioned2011-07-07T05:44:56Z
dc.date.available2011-07-07T05:44:56Z
dc.date.issued2011en_US
dc.description.abstractThe ability to measure location using time of flight in IEEE 802.11 networks is impeded by the standard clock resolution, imprecise synchronization of the 802.11 protocol, and the inaccuracy of available clocks. To achieve real-time location with accuracy goals of a few meters, we derive new consensus synchronization techniques for free-running clocks. Using consensus synchronization, we improve existing time of arrival (TOA) techniques and introduce new time difference of arrival (TDOA) techniques. With this common basis, we show how TOA is theoretically superior to TDOA. Using TOA measurements, we can locate wireless nodes that participate in the location system, and using TDOA measurements, we can locate nodes that do not participate. We demonstrate applications using off-the-shelf 802.11 hardware that can determine location to within 3m using simple, existing optimization methods. The synchronization techniques extend existing ones providing distributed synchronization for free-running clocks to cases where send times cannot be controlled and adjusted precisely, as in 802.11 networks. These location and synchronization techniques may be applied to transmitting wireless nodes using any communication protocol where cooperating nodes can produce send and receive timestamps.en_US
dc.identifier.urihttp://hdl.handle.net/1903/11695
dc.subject.pqcontrolledComputer Scienceen_US
dc.subject.pquncontrolledlocationen_US
dc.subject.pquncontrolledsynchronizationen_US
dc.subject.pquncontrolledwirelessen_US
dc.titleTime-based Location Techniques Using Inexpensive, Unsynchronized Clocks in Wireless Networksen_US
dc.typeDissertationen_US

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