Time Synchronization Device with Proactive Holdover Schedule
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Solution Overview
Problem
Conventional GNSS-based time synchronization methods face challenges in maintaining precision when navigation satellite signals are temporarily unavailable due to obstacles, leading to unstable system operation and potential deterioration in time synchronization precision.
Innovation Solution
A proactive holdover method is implemented, where a schedule is predetermined based on navigation satellite signal reception characteristics, allowing for switching between satellite signal synchronization and internal/external clock synchronization, ensuring high-precision time synchronization even in environments where the required number of navigation satellites cannot be captured.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a GNSS-based time synchronization method is used to achieve high-precision time synchronization, then time synchronization precision is improved, but reliability deteriorates when navigation satellite signals are blocked by buildings or trees in urban areas
Solution Approach 1:
The system performs preliminary actions by storing time information and frequency offset data obtained during periods when satellite signals are available. This preparatory storage of synchronization data allows the system to maintain time synchronization during signal outages without needing to react in real-time, thereby resolving the contradiction between achieving high precision and maintaining reliability in blocked environments.
Solution Approach 2:
The system changes operational parameters by switching between different synchronization modes (satellite signal-based vs. stored data-based) depending on signal availability. It adjusts the use of time information and frequency offset parameters dynamically, using satellite-derived parameters when available and transitioning to stored parameter usage when signals are blocked, thus maintaining both precision and reliability across different conditions.
2Reliability
If the system switches to holdover operation using internal or external clock signals when satellite signals are unavailable, then reliability is maintained, but time synchronization precision deteriorates over the holdover period
Solution Approach 1:
The system performs preliminary action by pre-storing accurate time information and frequency offset data during satellite signal availability. This advance preparation allows the holdover operation to use these pre-captured parameters, significantly extending the period during which high precision can be maintained compared to conventional holdover methods that rely solely on internal clock drift compensation.
Solution Approach 2:
The system implements feedback by continuously monitoring satellite signal availability and automatically switching between satellite-based synchronization and holdover operation using stored parameters. This feedback mechanism ensures that the system maintains the highest possible precision by using satellite data when available and seamlessly transitions to stored parameter usage when signals are blocked, thereby maintaining both reliability and precision.
3Adaptability or versatility
If reactive holdover switching is performed based on real-time reception state monitoring, then adaptability to signal conditions is improved, but system complexity increases due to continuous monitoring and switching control
Solution Approach 1:
The system reduces complexity by performing preliminary action - storing time information and frequency offset data in advance during satellite signal availability. This eliminates the need for complex real-time monitoring and switching logic, as the system can simply retrieve pre-stored parameters during holdover periods, thereby maintaining adaptability while significantly simplifying the control system.
4Measurement precision
If multiple navigation satellites are required to be captured simultaneously for time synchronization, then measurement precision is improved through delay correction, but ease of operation worsens in environments where line of sight is blocked
Solution Approach 1:
The system performs preliminary action by storing time information and frequency offset data obtained during periods when multiple satellites are visible. This advance storage eliminates the need to simultaneously capture multiple satellites during operation, allowing the system to maintain high precision using pre-captured data even when line of sight is blocked, thereby improving ease of operation while preserving measurement precision.
Data Source
AI summary
A time synchronization method that is capable of selecting whether synchronization, by a timepiece unit that generates a time signal synchronized with a standard time and outputs it to an exterior, with the time is performed by time information obtained by receiving a radio wave including information relating to the time, or is performed by means of a holdover performed using a clock signal from an internal or external clock source. A schedule having a first time period in which the above-mentioned time information is used, and a second time period by means of the holdover is determined according to temporal reception characteristics of the radio wave at a reception location of the radio wave, and according to the schedule, supplying the timepiece unit with the time information or supplying the timepiece unit with the clock signal from the internal or external clock source.