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International Journal of Navigation and Observation
Volume 2010 (2010), Article ID 149065, 17 pages
http://dx.doi.org/10.1155/2010/149065
Research Article

Nonlinear Filtering for Hybrid GPS/GSM Mobile Terminal Tracking

Communications Engineering Lab, Technische Universität Darmstadt, Merckstraße. 25, 64283 Darmstadt, Germany

Received 30 September 2009; Revised 16 March 2010; Accepted 1 June 2010

Academic Editor: Ronald Raulefs

Copyright © 2010 Carsten Fritsche and Anja Klein. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The Global Positioning System (GPS) has become one of the state-of-the-art location systems that offers reliable mobile terminal (MT) location estimates. However, there exist situations where GPS is not available, for example, when the MT is used indoors or when the MT is located close to high buildings. In these scenarios, a promising approach is to combine the GPS-measured values with measured values from the Global System for Mobile Communication (GSM), which is known as hybrid localization method. In this paper, three nonlinear filters, namely, an extended Kalman filter, a Rao-Blackwellized unscented Kalman filter, and a modified version of the recently proposed cubature Kalman filter, are proposed that combine pseudoranges from GPS with timing advance and received signal strengths from GSM. The three filters are compared with each other in terms of performance and computational complexity. Posterior Cramér-Rao lower bounds are evaluated in order to assess the theoretical performance. Furthermore, it is investigated how additional GPS reference time information available from GSM influences the performance of the hybrid localization method. Simulation and experimental results show that the proposed hybrid method outperforms the GSM method.