Abstract
This paper proposes a geometric method to locate a mobile station (MS) in a mobile cellular network when both the range and angle measurements are corrupted by non-line-of-sight (NLOS) errors. The MS location is restricted to an enclosed region by geometric constraints from the temporal-spatial characteristics of the radio propagation channel. A closed-form equation of the MS position, time of arrival (TOA), angle of arrival (AOA), and angle spread is provided. The solution space of the equation is very large because the angle spreads are random variables in nature. A constrained objective function is constructed to further limit the MS position. A Lagrange multiplier-based solution and a numerical solution are proposed to resolve the MS position. The estimation quality of the estimator in term of "biased" or "unbiased" is discussed. The scale factors, which may be used to evaluate NLOS propagation level, can be estimated by the proposed method. AOA seen at base stations may be corrected to some degree. The performance comparisons among the proposed method and other hybrid location methods are investigated on different NLOS error models and with two scenarios of cell layout. It is found that the proposed method can deal with NLOS error effectively, and it is attractive for location estimation in cellular networks.
Highlights
Wireless location for a mobile station (MS) in a cellular network has gained tremendous attention in the last decade due to support from the Federal Communication Commission (FCC) and wide range of potential applications using location-based information
In [15], by taking advantage of two time of arrival (TOA) seen at the two base station (BS) and angle of arrival (AOA) seen at home BS, the author proposed geometry-constrained location estimation (GLE) method to estimate the MS position
Where θd,i is the LOS path AOA and φi is the angle spread caused by NLOS propagation, which can be accurately described by a Gaussian random variable in a macrocell or outdoor environment
Summary
This paper proposes a geometric method to locate a mobile station (MS) in a mobile cellular network when both the range and angle measurements are corrupted by non-line-of-sight (NLOS) errors. A closed-form equation of the MS position, time of arrival (TOA), angle of arrival (AOA), and angle spread is provided. A Lagrange multiplier-based solution and a numerical solution are proposed to resolve the MS position. The scale factors, which may be used to evaluate NLOS propagation level, can be estimated by the proposed method. The performance comparisons among the proposed method and other hybrid location methods are investigated on different NLOS error models and with two scenarios of cell layout. It is found that the proposed method can deal with NLOS error effectively, and it is attractive for location estimation in cellular networks
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