Simulation And Analysis Of Autonomous Time Synchronization Based On Two-way Inter-satellite Link

Due to the significant contribution of satellite navigation system in the military field and thecivilian daily usage, most of the advanced countries have already begun their development onSatellite navigation system. The key technique of inter-satellite time synchronization is a criticalfactor in the autonomous operation of satellite navigation system. According to the developmentof constellation and operation system techniques in current China satellite navigation system.The research of this paper is specifically studied on the technology of autonomous timesynchronization based on inter-satellite link. The study and results shown in the following fourmain parts:(1) Take GPS constellation, For example, on the basis of inter-satellite link mode withmeasurement interval of6seconds, the inter-satellite link pseudo-range data is simulated, andthe random precision clock-error is reduced to less than0.1m with IGS precise ephemeris andprecision clock-error of172day in2007. Moreover, the clock-error of two-way inter-satellitelink with asychronization. To continue with the procedure, the study is then focused on theclock-error of two way inter-satellite link at different observation time. By doing so, theinter-satellite two-way time transfer calculation formula can be gradually built. Inter-satellitetwo-way time synchronization is simulated on the basis of IGS precise ephemeris and satelliteclock.(2) By studying the concept of time synchronization based on two way measurementsinter-satellites crosslink and observing inter-satellite two-way time transfer calculation formula,the main factor, which affects errors about the RMS of satellite clock-error are the system error.The system error is mainly caused by relativity theory effection and the multi-path; the epochdomestication of non-time synchronization crosslink pseudo-range is mainly caused by thenumerical calculation error.(3) After analyzing the error sources of measurements in inner-satellites crosslink,simulation results show that the relativity theory and multi-path can have great impaction onprecise clock error. The relativity theory is up to109s, and multi-path effection magnitude is upto107s. The correction can be achieved by obataining the fomula; position precision is set to1m and the speed precision of orbit is set to0.1mm/s. The satellites clock-error between eachother can be neglected as it is only1014influence. The7order Lagrange interpolation method isutilized to retrieve more accurate result in the process of epoch domestication.(4) The broadcast clock difference of each satellite is calculated by the "centralized" inter-satellite time synchronization.Compared with the IGS precise clock error, RMS of eachsatellite clock error is less than0.4ns.