Integrity performance characterization of BeiDou B1C and B2a signal-in-space error

Global Navigation Satellite System (GNSS) Signal-In-Space (SIS) quality directly affects positioning integrity, which is an important metric for safety–critical applications. BeiDou Global Navigation Satellite System (BDS-3) broadcasts two new signals interoperable with GPS and Galileo, i.e., B1C and B2a. They are expected to serve civil aviation applications, following the Standards and Recommended Practices (SARPs) released by International Civil Aviation Organization (ICAO). Therefore, the SIS accuracy and integrity performance of BDS-3 B1C and B2a are evaluated in this work. The SIS Range Errors (SISREs) are achieved by comparing the broadcast satellite positions and clock offsets derived from Civil Navigation Message (CNAV) with the precise products from International GNSS Service (IGS). Specifically, given that the IGS precise products are referring to the equivalent phase center of BeiDou Regional System (BDS-2) B1I + B3I ionosphere-free combination, Differential Code Bias (DCB) from IGS is applied to realize time synchronization. This synchronization method is also meaningful to different frequencies in other constellations and supports the en-route, approaching, and landing phases. By analyzing 1-year data, an overall SIS characteristic picture of the 18 BDS-3 MEO satellites is presented here. The results show that most BDS-3 satellites are subject to an overbounding User Range Accuracy (URA) of 0.5 m to 0.85 m and a fault probability of 1.4953×10^-5 to 1.1975×10^-4 , with an integrity performance much better than that of BDS-2 and comparable to that of GPS. BDS-3 is now ready to serve civil aviation and other safety–critical applications.