GNSS System Time Offset Monitoring And GNSS Time Comparison With Carrier-Phase

In order to achieve compatibility and interoperability between navigation systems,it is necessary to monitor the system time offset between navigation systems in real time.At present,the mainly way of GNSS system time offset monitoring is Signal-in-Space Reception method.This method is to obtain the positioning equation by using the multisystem receiver to receive the spatial signal,and obtain the GNSS time offset value by the parameter estimation method.The method is simple in operation and low in cost,and is the main method used in current GNSS time difference monitoring.In order to improve the accuracy of GNSS time offset monitoring,this paper uses high-precision carrier observation to improve the accuracy of GNSS time offset monitoring.The main contents of this article are as follows:(1)To solve the problem of the effect of pseudorange observation noise on GNSS time offset monitoring,the GNSS time offset monitoring method with phase-smoothed pseudorange is proposed.The method can reduce the influence of pseudorange observation noise on GNSS time offset monitoring by phase-smoothed pseudorange.The method is verified by measured data.It can be seen from the experimental results that the GNSS time offset monitoring method with phase-smoothed pseudorange can reduce the STD of the time offset monitoring value of BDS-GPS and BDS-Galileo to within 2 ns,and the accuracy is improved by more than 15%.(2)To reduce the influence of GLONASS IFB on GNSS time offset monitoring,this paper proposes a GNSS time offset monitoring method with GLONASS inter-frequency biases estimation.This method calculates the GLONASS IFB as the parameter when GNSS time offset parameter is estimated.The simulation experimental results show that this method can effectively reduce the RMS of GPS-GLONASS time offset value from 5.3ns to 0.03 ns,when the GLONASS IFBs are set as-7?6ns according frequency channel.The actual measurement results indicate that the difference of the results with GLONASS IFB and without GLONASS IFB is about 5ns.(3)For the real-time high-precision comparison between different nodes under the same time reference within the master station,this paper proposes the GNSS carrier phase single-difference time comparison method.With this method,the time comparison result with accuracy in sub-nanosecond order can be obtained in real time with only the broadcast ephemeris.This method can verify the fiber time comparison method in the master station.