Performance Analysis of BDS-3 PPP-B2b During the Satellite In-Orbit Upgrade Period

The satellite-based precise point positioning service represented by BeiDou third-generation (BDS-3) PPP-B2b provides all-day, high-availability, and weak communication-dependent precise positioning solutions for GNSS real-time undifferenced users. However, during the in-orbit upgrade and maintenance of BDS, the changes of GEO satellites for signal broadcast and the IGSO/MEO satellite PRN for SSR correction results in continuous fluctuations in service coverage, availability and service performance. Therefore, this paper uses the commercial receiver to measure the original channel encoding information, realizes the navigation message LDPC decoding and PPP-B2b message recovery and performs performance analysis. The results show that at least two GEO satellites continuously broadcast PPP-B2b correction messages during the upgrade periods. The average delay of B2b product recovery after a single satellite upgrade is about 1 h. After the upgrade of all satellites, the PDOP value of the service region is reduced by 12.5% on average. The static PPP experiments is carried out on the MGEX station in the IGS Asia-Pacific region for one month. The results show that the average horizontal and vertical convergence times are 35.83 and 15.35 min, and the average horizontal and vertical positioning accuracy are 2.12 cm and 2.77 cm, respectively, which are 17.2%, 11.68%, 26.9% and 40.5% lower than those before the upgrade.