Clock Drift Determination Using Signals of Opportunity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for determining clock drift between a local clock and a reference clock are prone to error when the device location changes, especially in scenarios where GNSS signals are lost, leading to timing inaccuracies due to ignored propagation delays.
Innovation Solution
A method that uses signals of opportunity (SoOps) from terrestrial or extra-terrestrial reference devices to calculate clock drift without requiring knowledge of the operating location, by constructing and solving simultaneous equations based on observed timing differences at calibration and operating locations, allowing for accurate timing synchronization even without GNSS reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If propagation delay is ignored to simplify timing estimation, then timing can be estimated even with unknown device location, but timing accuracy deteriorates due to unaccounted propagation delay
Solution Approach 1:
The device performs preliminary actions by measuring signal arrival times at multiple known reference positions before the actual operation. These preliminary measurements are used to calculate clock drift and propagation delay characteristics, which are then applied during operation to maintain timing accuracy without requiring continuous location knowledge.
Solution Approach 2:
The patent introduces an intermediary approach by using multiple reference positions and signal observations as mediators to indirectly determine timing parameters. Instead of directly measuring timing at the unknown operating position, the system uses intermediate measurements at known positions to infer the necessary timing information through calculated drift and propagation models.
2Measurement precision
If device location is assumed to remain fixed to maintain timing synchronization, then timing accuracy is preserved, but adaptability to movement deteriorates
Solution Approach 1:
The system implements feedback by continuously monitoring signal arrival times and comparing them against expected values based on the clock drift model. This feedback mechanism allows the system to detect and compensate for location changes, maintaining timing synchronization even as the device moves between different positions.
Solution Approach 2:
The patent applies dynamics by transitioning from a static timing assumption to a dynamic model that accounts for location changes. The system dynamically adjusts timing calculations based on observed signal characteristics and calculated propagation delays, enabling accurate timing maintenance during device movement rather than requiring fixed position.
3Measurement precision
If GNSS signals are used for timing calibration, then accurate timing can be achieved at calibration location, but reliability deteriorates when GNSS signals are lost
Solution Approach 1:
The patent uses signals from terrestrial or extra-terrestrial reference devices as intermediaries to establish timing relationships. These reference devices act as mediators that provide timing information independent of GNSS signals, enabling the system to maintain accurate timing even when GNSS is unavailable by using alternative reference sources.
Solution Approach 2:
The system achieves universality by designing a timing method that can function with multiple types of reference signals (GNSS, terrestrial, extra-terrestrial). This multi-functionality allows the same timing mechanism to operate reliably in diverse environments where different reference signals are available, ensuring continuous timing accuracy without dependency on a single signal source.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A method and apparatus for determining a drift between a local clock of a movable device and a reference clock that is used by one or more reference devices. The local clock may be calibrated at a calibration location and then the movable device may be moved to an operating location that is different from the calibration location. The drift is determined by observing one or more signals transmitted by the respective one or more reference devices, when the device is at the calibration location and when it is at the operating location. These observations are used together with a model of the signals to determine the drift.