Analysis on the time transfer performance of BDS-3 signals

Abstract

The BeiDou global navigation satellite system (BDS-3) was formally commissioned to provide positioning, velocity, and timing services to global users on 31 July 2020. We analyzed its pseudorange measurement noise, the precision of conventional common view (CV) and all-in-view (AV) time comparison, and the instability of the precise point positioning (PPP) time transfer to assess the time transfer performance of BDS-3. We found that the elevation-dependent biases found in BDS-2 code measurements are mitigated in BDS-3. The time transfer performance of the BDS-3 satellites is over 50% higher than that of the BDS-2 satellites. In terms of the CV time comparison, the standard deviations of the zero-baseline common clock time comparison of the new BDS-3 signal combination of B1C and B2a reach 0.36 ns, which are the same levels for Galileo E1 and E5a and the global positioning system (GPS) L1 and L2. In the long baseline AV comparison links over 7000 km, the standard deviation of the time comparison of the B1C and B2a combination also reaches 0.8 ns, and the improved gain is 55% relative to that of the BDS-2 B1I and B2I. We also tested the PPP time transfer performance with BDS-2 and BDS-3 satellites and found that the time transfer performance of BDS B1I and B3I is comparable to that of GPS L1 and L2.