Packet Network Clock Control via Autonomous Timing Validation
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Solution Overview
Problem
In packet networks, the reliability of timing information from multicast NTP and PTP servers is uncertain due to packet delay variation, leading to inaccurate data for client clocks, which compromises their stability and requires additional burden on primary tier sources.
Innovation Solution
A method that autonomously validates time and frequency data from multiple sources by performing offset measurements, minimum offset filtering, and frequency estimate filtering to generate reliable frequency estimates, allowing the use of less trustworthy timing sources like multicast NTP and PTP servers to supplement primary tier sources, thereby reducing costs and improving clock stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multicast NTP and PTP servers are used as timing sources, then cost and power consumption are reduced, but reliability and accuracy of timing information deteriorate due to packet delay variation
Solution Approach 1:
The patent applies preliminary action by performing validation and filtering operations on timing data before it is used by the client clock. The system pre-processes timing information from multicast sources through offset measurement, minimum offset filtering, and frequency estimate filtering to eliminate inaccurate data caused by packet delay variation, ensuring only validated timing data reaches the clock synchronization mechanism.
Solution Approach 2:
The patent introduces intermediary processing layers between the multicast timing sources and the client clock. These intermediaries include validation modules that perform offset measurements, minimum offset filtering, and frequency estimate filtering. These intermediary components act as mediators that transform unreliable multicast timing data into validated, accurate timing information suitable for clock synchronization.
2Adaptability or versatility
If packet-based methods are used to transport timing information, then adaptability to packet networks is improved, but measurement precision deteriorates due to packet delay variation
Solution Approach 1:
The patent implements feedback mechanisms through frequency estimate filtering that continuously monitors and adjusts timing data based on observed packet delay variations. The system measures offsets from multiple packets, filters out anomalies caused by network variability, and uses the filtered frequency estimates to correct timing deviations, creating a closed-loop feedback system that maintains precision despite packet-based transport challenges.
Solution Approach 2:
The patent applies partial action by selectively processing only the most reliable timing data. Through minimum offset filtering, the system identifies and processes only those packets with the smallest offsets (most likely to be accurate), discarding or de-weighting packets with larger offsets that are more likely to be affected by packet delay variation. This selective processing maintains measurement precision while working within the constraints of packet-based transport.
3Stability of the object's composition
If multiple filtering stages are applied to timing data, then frequency stability is improved, but processing time and computational load increase
Solution Approach 1:
The patent segments the filtering process into distinct, modular stages: offset measurement, minimum offset filtering, and frequency estimate filtering. Each stage processes timing data independently and sequentially, allowing for optimized computation at each step. This segmentation enables the system to apply multiple filtering operations while maintaining manageable processing time by breaking down the complex validation task into smaller, more efficient sub-tasks.
Data Source
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Figure 3A~3B
AI summary
One embodiment of the present invention sets forth a method for autonomously validating the time and frequency data obtained from multiple sources, and generating a suitable estimate of the frequency difference between the client clock and the source. The method includes the steps of protocol data unit validation (320), offset measurement (330), minimum offset filtering (340), and frequency filtering (350). With these steps, the negative effects of packet delay variation may be mitigated and a frequency estimate is determined for the source in question, together with an associated validity status. Consequently, quality control of the local clock is achieved in packet networks at significantly reduced cost and decreased level of complexity relative to prior art approaches.