BeiDou Receiver Autonomous Integrity Monitoring (RAIM) Performance Analysis

X-L. Su, X. Zhan, F. Qin, X. Zhang, Y. Zhang

Abstract:	The Global Navigation Satellite Systems (GNSS) have grown significantly over the last few years. GPS is modernizing by USA GPS Joint Program Office (GPS JPO). GPS.gov says 24 Block ? satellites should be operational by 2021. GLONASS was restored by Russian Federal Space Agency (RFSA). The Russian declared that the GLONASS constellation had reached the number of 24 operating spacecrafts by November 8, 2011. GLONASS provides 100% coverage of the Earth's surface now. Europe's Galileo satellite-navigation system is moving ahead by the European Commission (EC) and European Space Agency (ESA). A rapid launch plan is to begin initial navigation services by the end of 2014( orbit 18 satellites ), and acheive near-global coverage by the end of 2015(26 satellites ). The full constellation of 27 spacecrafts and three orbiting spares may be deployed by 2019. BeiDou Navigation Satellite System (BDS) is managed by China Satellite Navigation Office (CSNO). China released an official version of the complete Interface Control Document (ICD) for the nation’s BDS Open Service Signal-In-Space (SIS) on December 27, 2012 in Beijing. It outlines the specifications for the interface between the BeiDou SIS and user equipment, which will enable receiver designers and manufacturers to build BeiDou-capable receivers. By the end of 2012, there have been five GEO (geostationary earth orbit), four MEO (medium earth orbit) and five IGSO (inclined geosynchronous satellite orbit) BeiDou navigation satellites in orbit. Initial operating capability (IOC) of BeiDou Phase ? (with 14 satellites) in the Asia-Pacific region was attained. Full operating capability (FOC) for BeiDou global navigation system (Phase ? with 35 satellites) will be attained in 2020. The integrity is a major limitation for GNSS applying in these important applications fields. Receiver Autonomous Integrity Monitoring (RAIM) is the most direct, timely and computationally efficient integrity method. The RAIM algorithm is included within the receivers. Hence it is termed autonomous monitoring. It is a kind of intrinsic comprehensive fault detection capability of RAIM receiver. In aviation application, the RAIM performance is closely linked Required Navigation Performance (RNP). But the RAIM performances based on quality control method are of greater applicability in the broader GNSS application above mentioned. Applying the quality control theory into RAIM algorithm has been addressed in some current literatures. For example, Teunissen introduces Detection, Identification and Adaptation (DIA) procedure in detail. Due to the lack of integrity performances analysis literature about BeiDou, this paper focuses on assessing the RAIM availability and fault detection capability of BeiDou at the first time, and comparing them between BeiDou and GPS. The statistical methods of quality control are implemented to the integrity monitoring of GNSS. And four kinds of integrity monitoring parameters are introduced respectively. The RAIM performances are evaluated based on the Number of Visible Satellites (NVS) and Geometric Dilution of Precision (GDOP) as a measure of RAIM availability from satellites and constellation geometry configuration, Minimal Detectable Bias (MDB) and Minimal Detectable Effect (MDE) as a measure of the minimum fault detection capability of RAIM in the measurement level and navigation position level respectively. The achievable RAIM performance of the BeiDou14 (with 14 satellites), BeiDou (with 35 satellites) and GPS (with 31 satellites) are simulated with 5° masking angle when the pseudo-range standard deviations are equal to 1m and illustrated by the global, Asia-Pacific region and temporal variations respectively. The analyses of simulation results testify that the average RAIM performances in global for BeiDou are better than GPS’s except RAIM holes proportion in global because of 4 MEO satellites less. Moreover, the Asia-Pacific RAIM performances for BeiDou are more excellent than GPS’s in all indexes. The benefits of RAIM performances of BeiDou dedicate from GEO satellites and IGSO satellites. For BeiDou14 in Asia-Pacific region, RAIM availability from constellation geometry configuration and RAIM minimum fault detection capability are all better than GPS’s, but the BeiDou14 RAIM availability from satellites are worse than GPS’s. Concerning RAIM availability from satellites, the average global and Asia-Pacific NVS for BeiDou are 12.33 and 14.943, them for GPS are 9.970 and 9.256. But the average Asia-Pacific NVS for BeiDou14 are 7.609 which are less than them for GPS. With respect to the RAIM holes proportion, BeiDou constellations have 0.14% RAIM holes in the global, which is worse than GPS (0.02%) because BeiDou have 4 MEO satellites less than GPS. But in Asia-Pacific region, the BeiDou RAIM availability from satellites is 100%, the GPS’s and BeiDou14’s are 99.86% and 99.35% respectively. In regard to RAIM availability from constellation geometry configuration, the average global GDOP for BeiDou (1.992) are more excellent than GPS’s (2.528). The average Asia-Pacific GDOP for BeiDou (1.503) and BeiDou14’s (2.84) are all better than GPS’s (3.404) too. BeiDou have 100% RAIM availability from constellation geometry in Asia-Pacific region. The proportion of Asia-Pacific unavailable constellation geometry points for BeiDou14 (3.51%) is less than GPS (7.18%). As regards in global, the proportion of unavailable constellation geometry points for BeiDou (0.59%) is less than them for GPS (3.02%) too. But at some cities, for example Cape Town, the he proportion of unavailable constellation geometry points over 24h for GPS (0.28%) are better than them for BeiDou (1.44%). In relation to RAIM minimum fault detection capability, According to the results of the simulations, on the assumption that the pseudo-range standard deviations, the probability of the false alarm and the detection power are equal to 1m, 0.1% and 80% respectively, the detectable measurement bias (the maximum MDB) for BeiDou or GPS in global are 5.84m. In Asia-Pacific region, the maximum MDB for BeiDou descend to 5.40m. The position detectable deviation (the maximum MDE) for BeiDou and GPS in global are 9.80m and 18.54m respectively. In Asia-Pacific region, the maximum MDE for BeiDou, GPS and BeiDou14 are 1.86m, 18.56m and 9.80m. The methods and conclusions can be used for RAIM prediction and real-time assessment of BeiDou.
Published in:	Proceedings of the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2013) September 16 - 20, 2013 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	348 - 360
Cite this article:	Su, X-L., Zhan, X., Qin, F., Zhang, X., Zhang, Y., "BeiDou Receiver Autonomous Integrity Monitoring (RAIM) Performance Analysis," Proceedings of the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2013), Nashville, TN, September 2013, pp. 348-360.
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