Blind Mobile Positioning in Urban Environment Based on Ray-Tracing Analysis
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Blind Mobile Positioning in Urban Environment Based on Ray-Tracing Analysis Shohei Kikuchi,1 Akira Sano,1 and Hiroyuki Tsuji2 1 School
of Integrated Design Engineering, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan 2 Wireless Communications Department, National Institute of Information and Communications Technology (NICT), 3-4 Hikarino-Oka, Yokosuka, Kanagawa 239-0847, Japan Received 1 June 2005; Revised 27 October 2005; Accepted 13 January 2006 A novel scheme is described for determining the position of an unknown mobile terminal without any prior information of transmitted signals, keeping in mind, for example, radiowave surveillance. The proposed positioning algorithm is performed by using a single base station with an array of sensors in multipath environments. It works by combining the spatial characteristics estimated from data measurement and ray-tracing (RT) analysis with highly accurate, three-dimensional terrain data. It uses two spatial parameters in particular that characterize propagation environments in which there are spatially spreading signals due to local scattering: the angle of arrival and the degree of scattering related to the angular spread of the received signals. The use of RT analysis enables site-specific positioning using only a single base station. Furthermore, our approach is a so-called blind estimator, that is, it requires no prior information about the mobile terminal such as the signal waveform. Testing of the scheme in a city of high density showed that it could achieve 30 m position-determination accuracy more than 70% of the time even under non-lineof-sight conditions. Copyright © 2006 Hindawi Publishing Corporation. All rights reserved.
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INTRODUCTION
Interest in determining the position of wireless terminals has been growing rapidly for a number of wireless applications, such as location-based services, navigation, and security. In the United States, for example, the Federal Communications Commission (FCC) requires wireless carriers implementing enhanced 911 (E-911) service to provide estimates of a caller’s location within a given accuracy, for instance, wireless E-911 callers have to be located within 50 m of their actual location at least 67% of the time [1–3]. In Japan, there is a need to determine the locations of illegal wireless terminals on vehicles that are interfering with wireless communication systems [4]. Position determination is also needed for radiowave surveillance. The most widely used positiondetermination scheme is the global positioning system (GPS) [5]. Although it can be used to determine the locations of things highly accurately, existing handsets have to be modified to function as a GPS receiver, and it does not work unless the mobile terminal has a line-of-sight (LOS) path to the satellites [2]. Thus, it is not applicable to the detection of a nonsubscriber such as the radiowave surveillance. In a few decades, the use of array antennas is receiving much attention through the efficient
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