Virtual Atomic Clocks for Wide-Area Time Synchronization
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Solution Overview
Problem
Existing high-precision time synchronization methods, such as the Common-view and Precise Point Positioning methods, face challenges in achieving wide-area coverage and real-time synchronization due to high deployment and maintenance costs, limited spatial applicability, and long initialization times, especially in dynamic scenarios, and rely on atomic clocks that are not consistently synchronized across the network.
Innovation Solution
A high-precision time synchronization system using virtual atomic clocks, which generates virtual atomic clock observations by reconstructing reference station observations and eliminating ionospheric delays through ionosphere-free combinations, and employs Kalman filtering to estimate receiver clocks and tropospheric zenith information, allowing for rapid high-precision time synchronization without relying on physical atomic clocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If atomic clocks are introduced as time reference sources, then time synchronization precision is improved, but deployment and maintenance costs increase
Solution Approach 1:
The patent creates virtual atomic clocks that replicate the timekeeping function of physical atomic clocks through software and algorithmic processing. Instead of deploying actual atomic clocks at each reference station, the system uses GNSS observations and calibration data to generate virtual atomic clock signals that provide equivalent time synchronization precision at a fraction of the cost
Solution Approach 2:
The patent replaces expensive, maintenance-intensive physical atomic clocks with inexpensive virtual clock implementations that run on standard computing hardware. These virtual clocks can be easily deployed, updated, and replaced without the significant financial and logistical burden of physical atomic clock infrastructure
2Area of stationary object
If the baseline distance increases in CV method, then wide-area coverage is improved, but time synchronization performance deteriorates
Solution Approach 1:
The patent introduces virtual atomic clocks as intermediary time references that are mathematically constructed to be independent of baseline distance. These virtual clocks serve as stable time anchors that allow reference stations across wide areas to synchronize their clocks without the performance degradation that occurs in traditional CV methods when stations are far apart
Solution Approach 2:
The patent transforms the time synchronization approach by changing from direct physical clock comparison (which degrades with distance) to a mathematical model-based approach using virtual atomic clocks. This parameter change allows the system to maintain nanosecond-level precision across continental scales by using calibrated observation data and ionosphere-free combinations
3Area of stationary object
If PPP method is used for global time service, then coverage area is improved, but initialization time increases
Solution Approach 1:
The patent performs preliminary calibration of virtual atomic clocks using extensive GNSS observation data to establish accurate ionosphere-free combinations and clock offset models. This preliminary work is done offline or in advance, so that when real-time time synchronization is needed, the system can rapidly deliver results without requiring long initialization periods
Solution Approach 2:
The patent replaces the slow, iterative convergence process of traditional PPP methods with a direct computational approach using pre-calibrated virtual atomic clock models. Instead of requiring receivers to gradually converge on accurate time solutions through prolonged observation, the system uses mathematical models and calibration data to provide rapid, accurate time synchronization
4Area of stationary object
If multiple atomic clocks are introduced for wide-area application, then coverage area is improved, but system complexity and construction cost increase
Solution Approach 1:
The patent creates a universal virtual atomic clock framework that can serve multiple reference stations and applications simultaneously. Instead of requiring separate physical atomic clocks at each location, the system uses a single calibrated virtual clock model that can be applied across the entire network, reducing both the number of components and the overall system complexity
Data Source
AI summary
A high-precision time synchronization (HTS) system and method using virtual atomic clocks (VACs) includes: providing an implementation of VAC generation method: accessing the high-precision time service provided by the WPT system, solving receiver clock offsets and reconstructing reference stations observations; providing a rapid HTS method: using the VAC information to realize rapid HTS by means of pseudorange or carrier phase CV time transfer; obtaining a HTS system using VACs, including a real-time observations receiving and distributing module, a differential corrections receiving and decoding module, a local clock solving module, a GNSS observations reconstruction module, and a VAC data broadcasting module. Aiming at VACs don't have the function of time-keeping, and GNSS is easy to be interrupted by factors such as environmental and network anomalies, and a VAC is unable to continuously provide high-precision time service, combing VACs is proposed to safeguard the continuity and reliability of the time-frequency service system.