Because of its potential applications, mobile localization in wireless networks has attracted much attention recently. It is essential that a mobile user should be able to know its location anytime and anywhere. In practice, however, it is not always possible to obtain an accurate location of the mobile user; the presence of non-line-of-sight (NLOS) radio signal propagation and malicious beacons could cause considerable errors in localization. Therefore, NLOS identification and the detection of malicious beacons are important issues in localization. Existing NLOS identification methods usually assume that localization involving the use of NLOS radio signals cannot be performed in a consistent manner. However, the validity of the foregoing assumption has not been properly investigated. As a result, it is questionable whether these methods can be used to identify NLOS effectively. Existing malicious beacon identification methods require the cooperation of several detecting nodes for the verification of a location claim from a target node. They all suffer from one or both of the drawbacks: (i) not able to cope with a sparse network situation, and (ii) their design being based on a particular distance measurement technique. Moreover, even if NLOS propagation and malicious beacons can be identified, the following problem could arise: if the localization systems do not use the beacons involving NLOS propagation and the malicious beacons, they may not be able to locate a mobile user because of not having enough beacons. / In the first part of this thesis, we present a theoretical analysis of localization using NLOS radio signals, and show that the above-mentioned assumption would no longer be valid when the mobile user is located outside the convex hull of the underlying beacons. As a result, existing NLOS identification methods, as well as many localization approaches, could perform poorly. Extensive experiments on different wireless networks demonstrate that NLOS in localization and the localization error caused by NLOS have been greatly underestimated in previous studies. In the second part, we propose a general location verification scheme to identify malicious beacons. It employs a node-to-node approach for location estimation, and could use different measurement techniques; moreover, it supports secure location verification in sparse networks. The proposed verification scheme has been shown able to achieve satisfactory performance via extensive real world GPS-based wireless sensor network experiments. In the third part, we present a mobility enhanced localization (MEL) scheme. By introducing the user's mobility information into the localization process, the proposed MEL can work in the area where current mobile localization systems cannot locate a mobile user for not having enough beacons. Extensive real world GPS experimental results demonstrate the superiority of the proposed MEL scheme. With the proposed solutions to the above problems, we could obtain improved mobile localization. / Liu, Dawei. / Adviser: Moon-Chuen Lee. / Source: Dissertation Abstracts International, Volume: 73-03, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 90-97). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_344880 |
| Date | January 2010 |
| Contributors | Liu, Dawei, Chinese University of Hong Kong Graduate School. Division of Computer Science and Engineering. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, theses |
| Format | electronic resource, microform, microfiche, 1 online resource (x, 97 leaves : ill.) |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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