Hybrid Fault Detection Technique in Assisted GNSS

G. Ghinamo, G. Boiero, P. Lovisolo

Abstract:	High sensitivity GNSS receivers tracking weak signals have been developed for indoor applications and to operate in urban canyons. They allow tracking GNSS satellites when the signal is strongly attenuated by structures, walls and buildings. The signal at receiver level is distorted by many reflected components. A coherent error model depending on receiver C/N0 measurement for indoor and deep urban scenarios may take into account errors components due to thermal noise, short and medium multipath and it may be exploited in the navigation algorithms (i.e. WLS, kalman filter). Experimental results show that huge errors, not belonging to proposed statistics, may affect the pseudorange measurements. If a sufficient number of satellites signals is available, a monitoring technique, based on proposed error model has to be used for the integrity check of the signals (Receiver Autonomous Integrity Monitoring - RAIM) capable of detecting and isolating the observations that are degraded (Fault Detection Estimation - FDE). In challenging environment it is quite frequent that the number of available measurements allows integrity test execution but not isolation procedure: under these conditions additional information provided by Public Land Mobile Network (PLMN) may be used to isolate fault signal. In the paper asynchronous PLMN scenario is analyzed: a reference position is estimated, based on cell id and neighbouring cells power level measurement. The reference position in AGPS is usually transmitted by the network to the terminal. An FDE algorithm based on PLMN coarse reference position is proposed, the fault measurement is detected selecting the measurement subset generating the closest fix to the reference position. We investigate the benefits of this approach in an urban environment where the reference position is characterized by few hundreds meters accuracy. A field trial in Torino downtown proves that in urban environments reference position fault detection algorithm performs as well as chi square approach.
Published in:	Proceedings of IEEE/ION PLANS 2010 May 4 - 6, 2010 Renaissance Esmeralda Resort & Spa Indian Wells, CA
Pages:	765 - 770
Cite this article:	Ghinamo, G., Boiero, G., Lovisolo, P., "Hybrid Fault Detection Technique in Assisted GNSS," Proceedings of IEEE/ION PLANS 2010, Indian Wells, CA, May 2010, pp. 765-770. https://doi.org/10.1109/PLANS.2010.5507262
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