Time delay bias between the second and third generation of BeiDou Navigation Satellite System and its effect on precise point positioning

Abstract

To realize the deep integration of BeiDou-2 regional navigation satellite system (BDS-2) and BeiDou-3 global navigation satellite system (BDS-3), the time delay bias between BDS-2 and BDS-3 at the receiver side is analyzed for the joint BDS-2/BDS-3 precise point positioning (PPP). Twenty Multi-GNSS (Global Navigation Satellite System) Experiment tracking stations with different receiver types were selected to investigate the time-varying characteristics of time delay bias. We also make a comprehensive analysis about the influence of time delay bias on the ionosphere-free PPP and uncombined PPP. The results show that the daily mean values of time delay bias for consecutive days vary within 1 ns without apparent day-boundary discontinuities. In addition, the time delay bias for the receivers of the same brand can differ by several nanoseconds, especially for the TRIMBLE receivers. Without considering the time delay bias between BDS-2 and BDS-3, the pseudorange residuals, slant ionospheric delays, float ambiguities are subjected to change with the magnitude of the time delay bias, while the phase residuals and positioning accuracy are slightly affected. Moreover, the deviation of float ambiguity in ionosphere-free PPP caused by neglecting the time delay bias is larger than that of uncombined PPP.