An investigation of PPP time transfer via BDS-3 PPP-B2b service

Since 2020, China's Beidou has begun to provide an initial real-time precise point positioning (PPP) service via B2b signals for the Asia–Pacific region. It is expected to be used to achieve centimeter-level positioning and also brings opportunities for real-time time transfer. We collected 29 days of experimental data and compared it with the Centre National d’Etudes Spatiales (CNES) real-time products. The quality of the satellite's orbit and clock was analyzed first. Then, time transfer based on BDS-3, GPS, and BDS-3/GPS PPP was investigated. The results showed that the GPS PPP with the PPP-B2b is not recommended. The time transfer based on BDS-3 PPP using the PPP-B2a is feasible and achieves a 0.30 ns level. Importantly, the reliability of time transfer using the PPP-B2b outperforms that of PPP using CNES products due to the problem of unstable internet communication. Furthermore, compared to BDS-3-only, the precision of time transfer based on BDS-3/GPS PPP was not improved significantly.