Carrier phase common-view time transfer based on PPP with broadcast ephemeris

• The PPP time transfer was achieved by broadcast ephemeris. • Combined with PPP and common view, the carrier phase common-view time transfer is realized. • The optimal MDEV and threshold model to select common-view satellite is designed. • The new method is greatly improved compared with PPP by broadcast ephemeris. As a high-precision time transfer technique, GNSS PPP time transfer is widely used. However, in a delayed or limited network access environment, the satellite precise products required for PPP time transfer are unavailable. This paper proposes a carrier phase common-view time transfer method based on PPP with broadcast ephemeris. The method first performs time correction on the broadcast ephemeris and solves the PPP parameters. Then, all parameters except the receiver clock offset are substituted into the carrier phase observation equation to calculate the clock offset of the receiver relative to each satellite. Finally, the common-view method is employed, utilizing the optimal modified Allan variance and threshold model to select one satellite from the common-view satellites of both stations. Alternatively, it is also possible to use only BDS GEO satellites as common-view satellites to complete the process. The clock offsets of the two stations are subtracted to complete the time transfer. The experiment involved six IGS stations linked with UTC(k) and two stations equipped with external VCH-1008 hydrogen atomic clocks, forming four links. The results show that during the 30-day time transfer of the zero-baseline WDC5-WDC6, the time transfer standard deviation of this method reached 0.022 ns. Compared to broadcast ephemeris PPP, the time transfer precision of the four links improved by an average of 51 %. For average time intervals shorter than 3000 s, the frequency stability of the four links improved by an average of 85.8 % compared to broadcast ephemeris PPP. Additionally, the carrier phase common-view time transfer results using only the BDS C60 (GEO) satellite outperforming those obtained using BDS broadcast ephemeris PPP.