Clock Synchronization Using Delay-Selected Timing Messages
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Solution Overview
Problem
Existing frequency synchronization methods in data transfer networks are susceptible to disturbances caused by transfer delay variations, leading to over-reaction and inaccuracies, especially in technologies like ADSL and GPON, and are not suitable for applications where phase error accumulation is not limited.
Innovation Solution
A method and control device that form frequency-error indicators based on timing messages with similar transfer delays, using a frequency-controlled clock signal to achieve frequency-locking, while also forming phase-error indicators for phase-locking, allowing for the selection of timing messages with similar delays and reducing the impact of transfer delay variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase synchronization is achieved using conventional timing messages, then phase-locking between reference clock signal and phase-controlled clock signal is achieved, but the system becomes susceptible to transfer delay variations causing over-reaction and synchronization errors
Solution Approach 1:
The patent segments the timing message selection process by dividing timing messages into groups based on their transfer delay characteristics. Instead of using all timing messages or a simple fixed selection, the system segments them into categories (e.g., first group with smaller transfer delays, second group with larger transfer delays) and selectively uses messages from appropriate segments, thereby reducing the impact of transfer delay variations on phase synchronization accuracy.
2Measurement precision
If frequency synchronization is achieved using all received timing messages, then frequency-locking is achieved, but the system over-reacts to transfer delay variations causing frequency synchronization errors
Solution Approach 1:
The patent applies local quality by making the frequency error indicator calculation adaptive to local transfer delay conditions. Instead of uniformly processing all timing messages, the system identifies timing messages with similar transfer delay characteristics and uses only those for frequency error calculation. This localized approach ensures that frequency synchronization accuracy is maintained while eliminating the harmful effect of transfer delay variations that would otherwise cause over-reaction.
3Measurement precision
If phase-controlled clock signal is used for timing, then phase-locking is achieved, but phase-error accumulation occurs over long periods especially with small frequency errors
Solution Approach 1:
The patent introduces a frequency-controlled clock signal as an intermediary mechanism to prevent phase-error accumulation. The frequency error indicators, calculated from timing messages with similar transfer delays, control the frequency of this intermediary clock signal. By maintaining accurate frequency control through selective timing message usage, the system prevents the cumulative phase errors that would otherwise occur in phase-controlled systems over long durations, especially when small frequency errors persist.
Data Source
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AI summary
A device for controlling frequency synchronization comprises a processor (101) for controlling a frequency-controlled clock signal on the basis of received timing messages so as to achieve frequency-locking between the frequency-controlled clock signal and a reference clock signal. For the purpose of finding such timing messages which have experienced similar transfer delays and thus are suitable for the frequency control, the processor is configured to control a phase-controlled clock signal on the basis of the timing messages so as to achieve phase-locking between the phase-controlled clock signal and the reference clock signal, and to select the timing messages to be used for the frequency control on the basis of phase-error indicators related to the phase control. Thus, the phase-controlled clock signal is an auxiliary clock signal that is utilized for performing the frequency control.