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BDS-3 is now providing global positioning, navigation and timing (PNT) services. BDS-3 has new B1C, B2a and B2b signals compared to BDS-2. This work presents two single-frequency (SF) PPP time transfer models using BDS-3, B1C and B1I observations, and studies the performance of BDS-3 SF PPP time transfer by using 30-day data of 10 globally distributed stations from a multi-GNSS experiment (MGEX). We found that the ionospheric constraint SF PPP (SF1) time transfer model outperforms the method of SF PPP with the receiver clock offset at first epoch as the datum (SF2). Importantly, the statistical uncertainty of SF1 was less than 1 nanosecond, with (0.75, 0.71) ns in the average scheme for all time-links, using both B1I and B1C observations, respectively. The frequency stability of SF1 with B1C observations was improved from 1.73% to 13.04% in the short-term and from 0.88% to 17.49% in the long term, compared to that of B1I for all time-links. Hence, SF1 with B1C observations was recommended for SF PPP time transfer. [ABSTRACT FROM AUTHOR]

Single-frequency (SF) receivers are much cheaper than that of dual-frequency (DF). Even though DF precise point positioning (PPP) is nowadays applied in the time community, the cost of equipment is one of the key considerations for time users. Furthermore, the hardware delay calibration of single-frequency devices is simpler than that of dual-frequency devices. In addition, there is no literature to study real-time SF PPP time transfer. In this contribution, the possibility of time transfer using SF PPP was studied. The Un-combined SF PPP was employed for time transfer with ionospheric-constraint using real-time precise products. In this case, 18 multi-GNSS experiment (MGEX) stations and one time lab station were used to study real-time SF PPP time transfer using GPS, Galileo and BDS-2/3 satellites with 20-day. The results suggested that real-time single-frequency PPP can meet time transfer. the standard deviation (STD) of the clock difference obtained from GPS-only, Galileo-only and BDS-2/3 single-frequency PPP are about (0.51, 0.54, 0.91) ns, respectively. The frequency stability of real-time single-frequency PPP can achieve (1E-12, 1E-13, 1E-13) level at short-term and (1E-13, 1E-13, 1E-14) level at long-term, respectively, for BDS-2/3, Galileo-only and GPS-only based. [ABSTRACT FROM AUTHOR]