Fault Detection and Isolation in High-Sensitivity Assisted GPS

Heidi Kuusniemi, Helena Leppäkoski, Jari Syrjärinne and Jarmo Takala

Abstract:	The environment in personal positioning applications in urban areas places severe challenges for the positioning technologies due to satellite signal blockages, attenuation, deterioration, and multipath propagation. Obtaining an acceptable user position in these conditions is almost impossible with traditional, autonomous GPS (Global Positioning System) positioning. Assisted GPS (AGPS) is one of the most prominent technologies for recovering some of the positioning capability in the weak signal conditions. AGPS uses a wireless network as an alternative route to deliver the navigation data for position calculation and thus improves the sensitivity of the receiver. However, compared with a receiver operating with nominal signal levels, a highsensitivity AGPS receiver becomes more vulnerable to multipath reflections and false satellite acquisition. False acquisition will result in serious positioning errors if not taken into account properly. Thus, the use of high-sensitivity assisted GPS in an urban environment requires proper integrity monitoring to avoid obtaining erroneous position solutions. In this paper, the suitability of fault detection and isolation (FDI) for monitoring the navigation failures in an urban personal positioning application is studied. The FDI method presented here is based on the least-squares-residuals RAIM (Receiver Autonomous Integrity Monitoring) method. It uses an overdetermined position solution and least-squaresresiduals of range-type measurements to perform navigation consistency checks. The RAIM fault detection and isolation procedure designed for high-sensitivity AGPS has been implemented, tested, and evaluated with simulations and real-life navigation tests. The real-life tests consisted of pedestrian and vehicular navigation experiments that were carried out in an urban environment. The proposed method was able to detect reallife navigation failures, which occurred during the experiments. In many cases, the faulty signals were also successfully isolated, which made it possible to provide an acceptable user position in urban environment. The performed tests and simulations indicate that the RAIM algorithm lends itself to not only failure detection and isolation in aviation applications, but also to personal positioning FDI purposes.
Published in:	Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002) September 24 - 27, 2002 Oregon Convention Center Portland, OR
Pages:	2587 - 2595
Cite this article:	Kuusniemi, Heidi, Leppäkoski, Helena, Syrjärinne, Jari, Takala, Jarmo, "Fault Detection and Isolation in High-Sensitivity Assisted GPS," Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002), Portland, OR, September 2002, pp. 2587-2595.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In