Research on GNSS time offset monitoring based  on GLONASS IFBs

To enhance the compatibility and interoperability among GNSSs, it is necessary to monitor system time offset among GNSSs. At present, the main method of GNSS time offset monitoring is Signal-in-Space Reception method. Because of the FDMA technique, GLONASS satellites have different signal frequencies. It leads to IFBs for both pseudorange and carrier phase observations. The GLONASS IFBs will influence the GNSS-GLONASS system time offset monitoring. To reduce the impact of GLONASS IFBs, this paper proposes a method of GNSS time offset monitoring with GLONASS IFBs estimated. The simulation result indicates the accuracy of GPS-GLONASS time offset can be improved by more than 90％ on average.