Extended Kalman Filter Channel Estimation for Line-of-Sight Detection in WCDMA Mobile Positioning
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Extended Kalman Filter Channel Estimation for Line-of-Sight Detection in WCDMA Mobile Positioning Abdelmonaem Lakhzouri Institute of Communications Engineering, Tampere University of Technology, P.O. Box 553, 33101 Tampere, Finland Email: [email protected]
Elena Simona Lohan Institute of Communications Engineering, Tampere University of Technology, P.O. Box 553, 33101 Tampere, Finland Email: [email protected]
Ridha Hamila Etisalat College of Engineering, Emirates Telecommunications Corporation, P.O. Box 980, Sharjah, UAE Email: [email protected]
Markku Renfors Institute of Communications Engineering, Tampere University of Technology, P.O. Box 553, 33101 Tampere, Finland Email: [email protected] Received 21 October 2002 and in revised form 29 May 2003 In mobile positioning, it is very important to estimate correctly the delay between the transmitter and the receiver. When the receiver is in line-of-sight (LOS) condition with the transmitter, the computation of the mobile position in two dimensions becomes straightforward. In this paper, the problem of LOS detection in WCDMA for mobile positioning is considered, together with joint estimation of the delays and channel coefficients. These are very challenging topics in multipath fading channels because LOS component is not always present, and when it is present, it might be severely affected by interfering paths spaced at less than one chip distance (closely spaced paths). The extended Kalman filter (EKF) is used to estimate jointly the delays and complex channel coefficients. The decision whether the LOS component is present or not is based on statistical tests to determine the distribution of the channel coefficient corresponding to the first path. The statistical test-based techniques are practical, simple, and of low computation complexity, which is suitable for WCDMA receivers. These techniques can provide an accurate decision whether LOS component is present or not. Keywords and phrases: extended Kalman filter, fading statistics, LOS detection, mobile positioning, WCDMA systems.
1.
INTRODUCTION
For the public interest, mobile phone positioning in a cellular network with reliable and rather accurate position information has become unavoidable after the Federal Communications Commission mandate, FCC-E911 docket on emergency call positioning in USA, and the coming E112 in the European Union [1]. One method for locating the mobile station (MS) in two dimensions requires the measurement of line-of-sight (LOS) distance between the MS and at least three base stations (BSs). Hence, knowing which BS is reporting, LOS component is crucial for accurate position estimation. In many cases, the non-LOS (NLOS) signal compo-
nents, arriving with delay less than one chip at the receiver, obscure the LOS signal. This situation of overlapping multipath propagation is one of the main sources of mobile positioning errors [2, 3, 4]. Previous studies dealing with LOS detection used range measurement-based techniques [5, 6, 7] (i.e., measurements of the time of arri
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