Broadcast And Test Of BDS/GNSS Real-time Products For Precise Time Service

Precise Time Service based on iGMAS(PTS)is a standard time precision new timing method proposed by National Time Service Center,using carrier phase observation data,iGMAS(international GNSS Monitoring and Assessment System)analysis center real-time orbit products and clock products were reduced to UTC(NTSC),to achieve sub-nanosecond precision timing of UTC(NTSC).The paper is aimed at the construction of PTS prototype system,research the broadcasting and testing of BDS/GNSS real-time multi-GNSS orbit products,clock products and ionosphere products,which is of great significance for improving the timing reliability of PTS dual-frequency users and the timing availability of single-frequency users.The main research content and results of the thesis include:(1)Multi-GNSS real-time Precise Point Positioning(PPP)time transfer.Carrying out multi-GNSS real-time PPP time transfer test can explore the possible effects of multi-GNSS time service,verify the user's real-time PPP software,and provide reference for PTS user time service test.Adopting real-time orbit and clock products of Centre National d'Etudes Spatiales(CNES)analysis center of International GNSS Service(IGS)analysis center,7 GNSS tracking stations connected with high-precision atomic clocks are selected,and 365 days of Observation data,from two perspectives of different combinations of GNSS systems and changes in cut-off height angles,a variety of test strategies were designed and PPP solutions were made.The results show that standard deviation(STD)between the time transfer link result obtained by CNES realtime GPS-single system product and the time transfer link result obtained using IGR product is between 0.3 and 0.5 ns;Compared with the GPS-single system,real-time PPP time transfer using multi-GNSS products of multiple combination modes,STD decreased from IGR results.when the cut-off height angles are 10°,20°,30°,the percentages of STD improvement are 11.11～13.89%,10.81～ 16.21%,11.42～12.82%,respectively.(2)Real-time product broadcasting and optimization.Based on iGMAS National Time Service Center analysis center platform and BNC software,on the basis of original GPS-single system,it was adapted to broadcast BDS/GNSS multi-system realtime orbit products and multi-GNSS real clock products reduced to our country's standard time UTC(NTSC).For PTS single frequency users,added the realization of the real-time ionospheric product broadcasting of the analysis center of iGMAS National Time Service Center.In response to the problems of limited transmission speed of real-time precision products and the inability to resume broadcasting independently after the interruption of real-time data flow in PTS product transmission and broadcast sub-systems,the UDP data transmission program and automated operation program of PTS product transmission and broadcast sub-system were optimized and improved The transmission efficiency is achieved,autonomous operation is achieved,and the overall stability of PTS system is improved.At the user end,the real-time product reception test of the analysis center of iGMAS National Time Service Center was carried out.The results show that PTS product transmission and broadcast sub-system can continue to operate stably,and the broadcast content is accurate.(3)PTS user terminal timing test.Based on the real-time products of the analysis center of iGMAS National Time Service Center,the client's real-time PPP time service test was conducted online for 17 consecutive days.The results show that the complete rate of real-time GPS-single system products exceeds 90%,and the average STD values of the 17-day timing results of the five stations are all better than 1 ns.Based on the PTS system,real-time timing accuracy in the sub-nanosecond range can be achieved.