Link Profiling for GNSS-Independent Delay Compensation
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Solution Overview
Problem
Existing two-way time transfer protocols in communication networks struggle to handle dynamically changing and asymmetric link delays without relying on Global Navigation Satellite Systems (GNSS), which are vulnerable to jamming and spoofing, leading to inaccuracies in time synchronization.
Innovation Solution
A GNSS-independent method for asymmetry delay error compensation that involves establishing bidirectional virtual paths, monitoring data stream characteristics, and using delay correction factors to compensate for time errors, leveraging trusted sources like calibrated virtual paths or local clocks in holdover mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If two-way time transfer protocols assume link delay equals RTT/2, then the protocol complexity is reduced and ease of operation is improved, but measurement precision deteriorates due to inability to handle asymmetric delays
Solution Approach 1:
The system performs preliminary actions by establishing multiple bidirectional virtual paths and continuously monitoring their characteristics before time transfer operations. Link profiles are pre-established with monitored characteristics, and delay correction factors are pre-calculated based on these profiles. When a path becomes available, the system can immediately apply the appropriate correction factor without real-time calculation, thus maintaining both operational simplicity and measurement precision.
2Measurement precision
If GNSS systems are used for time synchronization, then time accuracy is improved, but reliability deteriorates due to vulnerability to jamming and spoofing
Solution Approach 1:
The system introduces intermediary elements in the form of multiple bidirectional virtual paths through which time transfer can occur. Instead of relying on a single external GNSS source that may be compromised, the system uses multiple intermediate communication paths with monitored characteristics. By selecting paths with favorable characteristics and applying delay correction factors, the system achieves accurate time synchronization without direct dependence on vulnerable external GNSS signals.
3Reliability
If multiple bidirectional virtual paths are established with monitoring and delay correction, then reliability and measurement precision are improved, but device complexity increases
Solution Approach 1:
The system creates simplified copies or representations of the complex network paths in the form of link profiles. Instead of managing the full complexity of multiple virtual paths directly, the system monitors path characteristics and stores them as simplified profiles containing key parameters. These profiles serve as manageable representations that enable the system to handle path selection and delay correction without being overwhelmed by the underlying complexity of the network infrastructure.
Data Source
AI summary
There is provided a GNSS independent method for asymmetry delay error compensation to minimize a time difference bias when using two-way time transfer in a communication network. The method includes establishing a bidirectional virtual path comprising at least one link path, LP1-LP4, over the network for communication between a first node A and a second node B by sending a bidirectional data stream over the virtual path and utilizing previously stored link profiles associated with a delay correction factor or a calibrated virtual path or a stable local clock in holdover mode to provide new delay correction factor to minimize a time difference bias in the local time in the second node.