Browsing by Author "Chen, Chao-Lin"

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An unified Kalman tracking technique for wireless location systems
(2007)
Tseng, Po-Hsuan
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Chen, Chao-Lin
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Feng, Kai-Ten
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電信工程研究所
;
Institute of Communications Engineering
Location estimation and tracking for the mobile stations have attracted a significant amount of attention in recent years. In order to offer sufficient precision for wireless location tracking, different techniques have been studied and combined, e.g. the Least Square methods for location estimation associated with the Kalman filters for location tracking. In this paper, an Unified Kalman Tracking (UKT) technique is proposed to provide an integrated algorithm for precise location estimation and tracking. Based on the Time-Of-Arrival (TOA) measurements, a new variable is incorporated as an additional state within the Kalman filtering formulation in order to consider the nonlinear behavior for wireless location estimate. Numerical results illustrate that the proposed UKT algorithm can achieve enhanced accuracy for mobile location tracking, comparing with other existing schemes.
Enhanced Location Estimation with the Virtual Base Stations in Wireless Location Systems
(2006)
Chen, Chao-Lin
;
Feng, Kai-Ten
;
電信工程研究所
;
Institute of Communications Engineering
Mobile location estimation has attracted a significant amount of attention in recent years. The network-based location estimation schemes have been widely adopted based on the radio signals between the mobile device and the base stations. The two-step Least Square (LS) method has been studied in related research to provide efficient location estimation of the mobile devices. However, the algorithm may results in inaccurate location estimation under (i) the existence of the Non-Line-Of-Sight (NLOS) errors and (ii) poor Geometric Dilution of Precision (GDOP) circumstances. A location estimation algorithm with the Virtual Base Stations (VBS) is proposed in this paper by considering the geometric layouts between the mobile device and its associated base stations. In order to enhance the precision of the location estimate, the VBS scheme is designed to incorporate the virtual base stations and the related geometric constraints within the formulation of the two-step LS method. The proposed VBS scheme can both preserve the computational efficiency from the two-step LS algorithm and obtain precise location estimation under poor GDOP and NLOS environments. Numerical results demonstrate that the proposed VBS algorithm can achieve better accuracy, comparing with other existing schemes, in mobile location estimation.
GALE: An enhanced geometry-assisted location estimation algorithm for NLOS environments
(2008-02-01)
Feng, Kai-Ten
;
Chen, Chao-Lin
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Chen, Chien-Hua
;
電信工程研究所
;
Institute of Communications Engineering
Mobile location estimation has attracted a significant amount of attention in recent years. The network-based location estimation schemes have been widely adopted based on the radio signals between the mobile device and the base stations. The two-step Least- Squares (LS) method has been studied in related research to provide efficient location estimation of the mobile devices. However, the algorithm results in insufficient accuracy for location estimation with the existence of Non-Line-Of-Sight (NLOS) errors. A Geometry-Assisted Location Estimation (GALE) algorithm is proposed in this paper with the consideration of different geometric layouts between the mobile device and its associated base stations. In order to enhance the precision of the location estimate, the GALE scheme is designed to incorporate the geometric constraints within the formulation of the two-step LS method. The algorithm can be utilized to estimate both the two-dimensional and the three-dimensional positions of a mobile device. The proposed GALE scheme can both preserve the computational efficiency from the two-step LS algorithm and obtain a precise location estimation under NLOS environments. Moreover, the Cramer-Rao Lower Bound (CRLB) for various types of measurement signals is derived to facilitate the performance comparison between different location estimation schemes. Numerical results illustrate that the proposed GALE algorithm can achieve better accuracy compared with other existing network-based location estimation schemes.
Wireless Location Estimation With the Assistance of Virtual Base Stations
(2009-01-01)
Chen, Chien-Hua
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Feng, Kai-Ten
;
Chen, Chao-Lin
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Tseng, Po-Hsuan
;
電信工程研究所
In recent years, wireless location estimation has attracted a significant amount of attention in different areas. Various types of radio signals are applied for the development of location-estimation algorithms. In this paper, the range measurements acquired from the received time-based information are adopted, and the modified least square (LS) method is utilized to process the raw data and to finally locate the target object. Practical issues, such as the nonline-of-sight (NLOS) errors and the geometric dilution of precision (GDOP) effect, are of concern. The NLOS error will cause a large nonnegative bias while measuring the propagation delay, which will lead to an unreliable result for location estimation. On the other hand, a large GDOP value corresponds to a poor geometric topology, which will result in inferior performance by adopting most of the existing location algorithms. The proposed location-estimation algorithms with virtual base stations (VBSs) will both mitigate the influence from the NLOS errors by imposing the geometric constraints and reduce the GDOP effect by incorporating the assisted VBSs. Two iterative schemes are proposed, including the center-of-gravity-based VBS (VBS-CG) and the minimal GDOP-based VBS (VBS-MG) algorithms, to determine the required number and the locations of the assisted VBSs. The proposed VBS algorithms are compared with other existing location-estimation schemes via simulations. The performance of the VBS-MG algorithm is observed to outperform the other schemes, particularly under the environments with larger NLOS errors and poor geometric layouts.
Wireless Location Tracking Algorithms for Environments with Insufficient Signal Sources
(2009-12-01)
Tseng, Po-Hsuan
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Feng, Kai-Ten
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Lin, Yu-Chiun
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Chen, Chao-Lin
;
電信工程研究所
Location estimation and tracking for the mobile devices have attracted a significant amount of attention in recent years. The network-based location estimation schemes have been widely adopted based on the radio signals between the mobile device and the base stations. The location estimators associated with the Kalman filtering techniques are exploited to both acquire location estimation and trajectory tracking for the mobile devices. However, most of the existing schemes become inapplicable for location tracking due to the deficiency of signal sources. In this paper, two predictive location tracking algorithms are proposed to alleviate this problem. The Predictive Location Tracking (PLT) scheme utilizes the predictive information obtained from the Kalman filter in order to provide the additional signal inputs for the location estimator. Furthermore, the Geometric-assisted PLT (GPLT) scheme incorporates the Geometric Dilution of Precision (GDOP) information into the algorithm design. Persistent accuracy for location tracking can be achieved by adopting the proposed GPLT scheme, especially with inadequate signal sources. Numerical results demonstrate that the GPLT algorithm can achieve better precision in comparison with other network-based location tracking schemes.