More robust high precision time synchronization system

High-precision synchronous networks, as an essential foundational support network for the industrial application of 5G networks, must have robust security and resilience, which are one of the important requirements for network construction. To enhance the robustness of high-precision time synchronization in 5G systems and to address the issue of satellite coverage blind spots, thereby minimizing the dependency of time and frequency synchronization terminals on the Global Navigation Satellite System (GNSS), this paper proposes the use of cesium clocks as an external reference frequency source to integrate with time and frequency synchronization terminals to achieve high-precision time synchronization and timekeeping technology. When satellite signals are available, satellite timing signals provide time and phase information, and the external reference frequency source provides frequency information, to achieve high-precision time-frequency synchronization; when the satellite signal is unavailable, the output of the time-scale module of the system is compensated by the clock difference of the forecast external reference frequency source to achieve long-term timekeeping. Experimental results show that with the cesium clock as the external reference frequency source integrated with the time and frequency synchronization terminal continuously tracing for three days, the system output 1PPS and UTC(NIM) clock difference peak value is better than 15 ns; the timekeeping error over 14 days is less than 50ns.