Clock Synchronization with Skew and Offset Correction
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Solution Overview
Problem
Existing clock synchronization methods, such as IEEE 1588 PTP, assume only an offset between clocks, neglecting the inherent skew that causes clocks to drift apart, leading to inaccurate synchronization, especially in critical applications requiring stringent synchronization margins.
Innovation Solution
A method that estimates both the clock skew and offset by analyzing timestamps from message exchanges between a time server and client, using representative delay values to adjust the local clock for precise synchronization, ensuring long-term reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If IEEE 1588 PTP assumes only offset between clocks, then the synchronization method is simple, but the synchronization accuracy deteriorates due to neglecting clock skew
Solution Approach 1:
The patent changes the synchronization model by introducing clock skew as an additional parameter alongside offset. The system now estimates both offset and skew parameters from timestamp measurements, transforming the synchronization approach from single-parameter to multi-parameter estimation, thereby improving accuracy without excessive complexity increase
Solution Approach 2:
The patent adds a temporal dimension to the synchronization correction by accounting for clock skew, which represents frequency drift over time. This transforms the correction from a static offset adjustment to a dynamic correction that evolves with time, capturing the second-order effect of clock divergence
2Measurement precision
If GPS receivers with high specification are used, then synchronization accuracy is improved to sub-100 nanosecond levels, but the cost and infrastructure requirements increase significantly
Solution Approach 1:
The patent employs standard packet network infrastructure and software-based timestamping instead of expensive GPS hardware with specialized oscillators and antenna systems. The solution uses readily available network equipment to achieve high synchronization accuracy, replacing costly dedicated synchronization hardware with general-purpose computing resources
Solution Approach 2:
The patent replaces the physical GPS satellite-based timing system with a software-based network protocol solution. Instead of relying on electromagnetic signals from satellites and specialized hardware timestamping, the system uses IP network message exchanges with software timestamping and algorithmic correction to achieve synchronization
Data Source
AI summary
This invention relates to methods and devices for clock synchronization. The invention makes particular use of IEEE 1588 with offset and skew correction. In embodiments of the invention, the IEEE 1588 Precision Time Protocol is used to exchange time stamps between a time server and a client from which the client can estimate the clock offset and skew. In embodiments of the invention a free running clock at the client is provided with an estimation technique based on the time stamps from the IEEE 1588 PTP message exchange between the server and client clocks. The offset and skew from the estimation process can be combined with the local free running clock to give a synchronized local clock which is an accurate image of the master clock.