Time Synchronization Optimization Method for Railway Communication and Navigation System in Satellite Denial Environments

The integrated railway communication and navigation system can provide auxiliary navigation and positioning services for trains in the satellite signal rejection environments. The basis for the autonomous operation of the communication and navigation system is the high-precision time synchronization between each node in the system. In order to improve the accuracy of the time synchronization, this paper proposes a broadcast-like joint physical time synchronization and ranging method for railway communication and navigation system. Firstly, the high stability clock parameters are obtained by inverting the measured data of the Allen variance of the real clock, and the state equation of the two-way ranging model is improved by introducing the parameter error correction, so as to realize the joint estimation of the clock parameters and the ranging parameters. Secondly, the broadcast-like protocol is designed to reduce the communication links and reduce the communication overhead. Finally, the closed-loop model of “two-way communication-clock parameters estimation-physical clock adjustment-two-way communication” is established to eliminate the impact of clock parameters on the system performance from the source, and to achieve a high-precision and low-energy time synchronization system.