The millisecond-level alignment of LED network synchronous clocks requires the joint action of key technologies such as multi-source time service coordination, high-precision local clocks, stable jitter control, reliable power supply and automated management. The specific implementation methods are as follows:
1. Multi-Source Time Service Coordination and Trusted Source Selection
• Core time service source: Adopt satellite time service systems such as GPS and BDS as the main time service source, whose time accuracy can reach the nanosecond level, providing a foundation for millisecond-level alignment. The satellite signal is parsed by a dedicated receiving module and directly calibrates the local clock source.
• Standby time service source: Integrate network time service methods such as NTP (Network Time Protocol) and 4G/WiFi as supplements. When satellite signals are lost or interfered, the system automatically switches to the standby source and compensates for network transmission delay through algorithms (the NTP synchronization accuracy is usually in the range of 1-50 milliseconds).
• Dynamic source switching mechanism: Real-time evaluate and select the optimal time service source according to parameters such as signal quality (e.g., signal-to-noise ratio, packet loss rate) and time service source stability. For example, in scenarios with satellite signal occlusion, NTP + 4G dual backup time service is preferred to ensure time continuity.
2. High-Precision Local Clock and Timing Ability
• Hardware-level clock source: Adopt Temperature-Compensated Crystal Oscillator (TCXO) or Oven-Controlled Crystal Oscillator (OCXO) as the local clock reference, whose frequency stability can reach ±0.1ppm (parts per million) or even higher, reducing clock drift caused by temperature changes.
• Software-level time compensation algorithm: Dynamically adjust the local clock frequency through the PID control algorithm to compensate for the cumulative error during the interval of time service signals. For example, when satellite signals are interrupted, the system relies on the local clock for timing, and the monthly error can be controlled within ±10 milliseconds.
• Distributed clock synchronization protocol: In the local area network, adopt PTP (Precision Time Protocol) or gPTP (General Precision Time Protocol) to realize microsecond-level synchronization between devices, further narrowing the time difference of multi-screen display.
3. Stable Jitter Control and Transmission Optimization
• Time service signal de-jitter processing: Perform filtering processing (e.g., Kalman filter) on the received time service signals to eliminate instantaneous errors caused by signal interference or sudden changes in transmission delay. For example, compress the jitter range of NTP time service from ±50 milliseconds to within ±5 milliseconds.
• Data transmission link optimization: Adopt a low-latency network architecture (e.g., SDN Software Defined Network) to reduce packet forwarding delay; mark key time synchronization data packets with high priority to ensure their transmission real-time.
• Synchronous trigger mechanism: In scenarios requiring strict synchronization (e.g., multi-screen linkage display), realize millisecond-level event synchronization through hardware synchronous signal lines or wireless triggers to avoid the uncertainty of software layer scheduling.
