Characteristics of BDS Signal-in-Space User Ranging Errors and Their Effect on Advanced Receiver Autonomous Integrity Monitoring Performance

Signal-In-Space User Range Errors (SIS UREs) are assumed to be overbounded by a normal distribution with a standard deviation represented by the User Range Accuracy (URA). The BeiDou Navigation Satellite System (BDS) broadcast URA is not compatible with the historical SIS URE performance that affects the Advanced Receiver Autonomous Integrity Monitoring (ARAIM) False Alert Probability (Pfa) and availability evaluation. This study compares the BDS broadcast and precise ephemeris from 1 March 2013 to 1 March 2017 to obtain SIS UREs. Through analyzing the statistical characteristics of the SIS UREs, we obtain the standard deviation sigma(URE) for the accuracy and continuity and sigma(URA) used for the integrity of the SIS UREs. The results show that the broadcast sigma(URA) of 2 m cannot completely overbound SIS UREs for all BDS satellites, but the sigma(URA) of 2.4 m can. Then, we use the sigma(URA) of 2.4 m to evaluate the ARAIM Pfa and availability. The results show that the Pfa may increase to 2 x 10(-5) and exceed its limit by an order of magnitude. We also consider the differences between the SIS UREs of Geostationary Earth Orbit (GEO), Inclined Geo-Synchronous Orbit (IGSO), and Medium Earth Orbit (MEO). The results indicate that all Pfa values calculated by the computed sigma(URE) are less than the Pfa in the Integrity Support Message (ISM) for the worst-performing GEO satellite. The approximately 55% Pfa calculated by the computed sigma(URE) is less than the Pfa in ISM for the worst-performing IGSO satellite. Most Pfa values calculated by the computed sigma(URE) is less than the Pfa in the ISM for the worst-performing MEO satellite. For BDS satellites, the Pfa is mainly affected by sigma(URE). When the sigma(URA) of 2.4 m is used to evaluate the availability, the computed availability is lower than the availability calculated by the broadcast sigma(URA)/sigma(URE) and the greatest degradation can reach 25%.