Virtual Path Delay Compensation for Asymmetric Time Synchronization
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Solution Overview
Problem
Existing two-way time transfer protocols struggle to handle dynamically changing and asymmetric link delays in communication networks, which disrupt accurate time synchronization.
Innovation Solution
A method that utilizes calibration profiles associated with virtual paths between nodes to identify and select the best paths, compensating for asymmetry by using delay correction factors, ensuring all paths are calibrated and using accurate time offsets for synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If two-way time transfer protocols assume symmetric delays (RTT/2), then the protocol complexity is reduced and operation is simplified, but time synchronization accuracy deteriorates when asymmetric delays occur
Solution Approach 1:
The system performs preliminary calibration of delay values between nodes before actual time transfer operations. Calibration profiles storing delay correction factors are established in advance through calibration procedures, allowing the system to pre-compute and store accurate delay characteristics for multiple virtual paths. This preliminary action eliminates the need for real-time symmetric delay assumptions during operational time transfer.
Solution Approach 2:
The system changes the delay parameter from a fixed symmetric assumption (RTT/2) to variable calibrated delay values. By implementing calibration profiles that store specific delay correction factors for different virtual paths and conditions, the system dynamically adjusts the delay parameter based on actual measured characteristics rather than relying on theoretical symmetric assumptions.
2Reliability
If calibration profiles are stored for multiple virtual paths, then time synchronization reliability is improved under changing conditions, but device complexity increases
Solution Approach 1:
The system segments the time synchronization problem by creating separate calibration profiles for different virtual paths between nodes. Each profile contains delay correction factors specific to that path, allowing independent calibration and selection. This segmentation enables the system to handle multiple paths with different characteristics without requiring a single complex unified model.
Solution Approach 2:
The system creates copies of calibration data in the form of calibration profiles for different virtual paths. Instead of computing delay values in real-time, the system pre-computes and stores copies of delay correction factors that can be quickly retrieved and applied during time transfer operations, reducing computational complexity while maintaining accuracy.
3Measurement precision
If dynamic asymmetry in link delays is handled by continuous recalibration, then time synchronization accuracy is maintained, but loss of time increases due to frequent calibration operations
Solution Approach 1:
The system performs calibration actions in advance and stores the results in calibration profiles. By pre-computing delay correction factors and storing them for multiple virtual paths, the system eliminates the need for continuous real-time recalibration during operational time transfer, reducing time loss while maintaining accuracy through pre-prepared calibration data.
Solution Approach 2:
The system implements dynamic selection of calibration profiles based on current network conditions rather than continuous recalibration. The node can dynamically choose the most appropriate calibration profile from stored options based on active virtual paths and current conditions, maintaining accuracy without the time overhead of continuous calibration operations.
Data Source
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AI summary
There is provided an asymmetric link delay compensation method in which a plurality of calibration profiles may be used for providing a common network time estimate in a communication network 100. The communication network comprises a node (130) having at least two virtual paths, VP, (VP1, VP2) connecting to one or more sync nodes (122). The at least two VPs are each associated with one or more respective predetermined calibration profiles with a respective delay correction factor. By identifying which of the VPs may be candidate VPs for calculating a time offset caused by the delay over the VPs and then ranking the candidates to select a best or a set of candidates for the calculation, an advantageous method for providing a common network time in the communication network is achieved.