Local Oscillator Holdover with Built-In Timing Model Self-Test

Solution Overview

Problem

Network nodes with local oscillators disciplined by external timing references face performance impairment when the external reference is unavailable, requiring costly and time-consuming human intervention to maintain timing accuracy, especially in stringent standards like WiMAX and LTE where time errors must be limited to microseconds over hours.

Innovation Solution

A method that trains mathematical models of the local oscillator using external reference signals to predict correction signals, calculates and integrates frequency errors, and selects the model with the smallest time error to maintain oscillator discipline without external references, allowing for automatic holdover operation within specified error thresholds.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If an external timing reference source is used to discipline the local oscillator, then timing accuracy is improved, but the system becomes vulnerable to performance impairment when the external reference is unavailable

Engineering Contradiction:

Improvetiming accuracyVSAvoidoperational reliability during reference unavailability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The system performs preliminary training of mathematical models during periods when the external reference is available. Correction signals are sampled and stored, and models are trained in advance so that when the reference becomes unavailable, the pre-trained models can immediately provide accurate predictions without requiring real-time external input.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system creates mathematical models that replicate the behavior of the external reference signal's effect on the oscillator. These models capture the correction patterns and can generate predicted correction signals that mimic the external reference's disciplining effect, allowing the oscillator to maintain accuracy even when the actual external reference is unavailable.

Inventive Principle:

Principle #26Copying

2Reliability

If human intervention is used to correct timing when external reference is unavailable, then timing errors can be corrected, but the process becomes time-consuming and costly

Engineering Contradiction:

Improvetiming correction capabilityVSAvoidtime for human intervention

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system implements self-service through automated mathematical models that continuously monitor oscillator performance and generate correction signals without human intervention. The models automatically detect timing drift, compute corrections based on trained parameters, and apply corrections in real-time, eliminating the need for manual timing adjustments while maintaining accuracy.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The system establishes a feedback loop where the mathematical models continuously compare predicted oscillator behavior against actual performance, automatically generating and applying correction signals. This closed-loop control system detects and corrects timing errors in real-time without requiring external human intervention, maintaining timing accuracy autonomously.

Inventive Principle:

Principle #23Feedback

3Measurement precision

If multiple mathematical models are trained and tested, then the most accurate model can be selected, but the complexity of the system increases

Engineering Contradiction:

Improveprediction accuracyVSAvoidmodel selection complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system implements self-service through automated mathematical models that continuously monitor oscillator performance and generate correction signals without human intervention. The models automatically detect timing drift, compute corrections based on trained parameters, and apply corrections in real-time, eliminating the need for manual timing adjustments while maintaining accuracy.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The system establishes a feedback loop where the mathematical models continuously compare predicted oscillator behavior against actual performance, automatically generating and applying correction signals. This closed-loop control system detects and corrects timing errors in real-time without requiring external human intervention, maintaining timing accuracy autonomously.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS7915962B2System and method for built in self test for timing module holdover

Publication Date: 2011.03.29 MALIKIE INNOVATIONS LTD

AI summary

Embodiments of the invention include a method for use in a device having a local oscillator. The method includes performing, for the local oscillator that is disciplined by an external reference signal, while locked to the external reference signal, training at least two mathematical models of the oscillator to determine a predicted correction signal for each mathematical model based at least in part on a correction signal that is a function of the external reference signal and which is used to discipline drift in the oscillator. The method also includes selecting a mathematical model of the at least two mathematical models that results in a smallest time error when disciplining the oscillator to use when the external reference signal is unavailable and an alternative correction signal is to be used to discipline drift in the oscillator. The method further includes testing the selected mathematical model using a sampled version of the correction signal such that the selected mathematical model can be used without the need for a testing duration that is in addition to a period of time used for the training.