Assessment of the BDS-3 on-board clocks and their impact on the PPP time transfer performance. (1st March 2020) - Qin, Weijin
Graphical abstract: Highlights: BDS-3 on-board clock was evaluated and compared to GPS/GLONASS/Galileo/ BDS-2. The prediction accuracy of BDS-3 satellite clock was investigated and presented. The performance of BDS-3 PPP time transfer was studied and assessed. Abstract: The atomic clock is the heart of a satellite navigation system and limits the user positioning, navigation and timing (PNT) accuracy; hence, it is necessary to acquire more information about the BDS-3 on-board clocks. In this contribution, sixty days of BDS-3 clock results were analyzed in terms of their stability and prediction accuracy and compared with the results from BDS-2 (BDS: BeiDou Navigation Satellite System), GPS (Global Positioning System), GLONASS (Global Navigation Satellite System) and Galileo clocks. The results show that BDS-3 clocks have greater stability than BDS-2 and BDS-3 s clocks, GPS Block IIA, Block IIR, and Block IIR-M clocks, and GLONASS clocks, while their stability is comparable to that of Block IIF clocks and inferior to that of Galileo clocks. In comparison with the stability of BDS-2 clocks, the percentages of improvement in the stability of BDS-3 clocks range from 5% to 65%. Overall, the stabilities of BDS-3 clocks at 1000 s, 10000 s and 86400 s are nearly 3 ~ 6E-14, 2 ~ 8E-14 and 1 ~ 24E-14, respectively. Furthermore, the prediction accuracy of BDS-3 clocks is 0.24 ns, which is smaller than that of BDS-2 and GPS clocks. Finally, preliminary experiments were conducted with regard to precise point positioning (PPP) time transfer using BDS-3 signals. The four solutions, namely, the BDS-2, BDS-2 + BDS-3, BDS-3, and GPS solutions, were compared in terms of their frequency stability. As a slight imperfection, BDS-3 applications are restricted by the limited number of satellites. Nevertheless, the link results based on BDS-3 are more stable than those based on BDS-2 and BDS-2 + BDS-3. In particular, the BDS-3 results outperform the GPS results in their long-term stability. At typical averaging times, namely, 1000 s, 10, 000 s, and 86, 400 s, in comparison with the GPS results, the percentages of improvement in the link stability are 22.91, 38.40 and 19.03%, respectively, while those in comparison with the BDS-2 results are 40.08, 34.06 and 10.90%, respectively.