Oscillator Calibration via Network Time Protocol

Solution Overview

Problem

Conventional oscillators required for high-frequency accuracy in basestations, such as femtocell basestations, are expensive, making them impractical for smaller user bases, and existing cost-reduction methods lack effective automated calibration solutions.

Innovation Solution

A method using timestamped response messages from a network time server to determine the accuracy of an oscillator by calculating network propagation delays, selecting messages with minimal jitter, and adjusting the oscillator based on changes in these delays, allowing for automated calibration without user intervention.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a conventional accurate oscillator is used in a basestation, then frequency accuracy is improved, but cost increases

Engineering Contradiction:

Improvefrequency accuracyVSAvoidcost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent replaces expensive conventional oscillators with inexpensive oscillators that have inherent frequency inaccuracies. These low-cost oscillators are continuously calibrated using network time protocol data from time servers, allowing the system to maintain high frequency accuracy without requiring expensive hardware components.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent implements a feedback mechanism where the oscillator's frequency accuracy is continuously monitored and adjusted based on time difference measurements from network time servers. The controller receives timestamped response messages, calculates propagation delays, and uses this information to correct the oscillator's frequency drift, creating a closed-loop calibration system.

Inventive Principle:

Principle #23Feedback

2Ease of manufacture

If a low-cost inaccurate oscillator is used, then cost is reduced, but frequency accuracy deteriorates

Engineering Contradiction:

ImprovecostVSAvoidfrequency accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent implements a feedback mechanism where the oscillator's frequency accuracy is continuously monitored and adjusted based on time difference measurements from network time servers. The controller receives timestamped response messages, calculates propagation delays, and uses this information to correct the oscillator's frequency drift, creating a closed-loop calibration system.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the operational parameters of the low-cost oscillator through continuous frequency adjustment based on calibration data. By dynamically modifying the oscillator's frequency parameters according to measured time differences and propagation delays, the system transforms an inaccurate oscillator into an accurate timekeeping device.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If manual calibration methods are used, then frequency accuracy can be maintained, but operational complexity and time consumption increase

Engineering Contradiction:

Improvefrequency accuracyVSAvoidoperational complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent implements self-service calibration where the basestation automatically performs frequency calibration using network time protocol without requiring user or operator intervention. The system autonomously exchanges timestamped messages with time servers, processes calibration data, and adjusts the oscillator frequency automatically, eliminating manual calibration operations.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent implements a feedback mechanism where the oscillator's frequency accuracy is continuously monitored and adjusted based on time difference measurements from network time servers. The controller receives timestamped response messages, calculates propagation delays, and uses this information to correct the oscillator's frequency drift, creating a closed-loop calibration system.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8301181B2Oscillator calibration

Publication Date: 2012.10.30 UBIQUISYS LIMITED A BRITISH

AI summary

A basestation for a cellular communication system has an interface, for connection to a computer network, and also includes an oscillator, for generating wireless transmit and receive frequencies. A controller receives timestamped response messages from a time server over the computer network, each response message being subject to a network propagation delay, which is a sum of a minimum network propagation delay and a jitter component. For each received response message an apparent network propagation delay is determined as a function of a difference between a first timestamp applied by the time server and a second timestamp based on a clock derived from said oscillator. A subset of the received response messages are selected, whose network propagation delays include minimal jitter components. The frequency accuracy of the oscillator is then determined based on changes over time in the apparent network propagation delays of the selected received response messages. The oscillator can then be adjusted based on this frequency accuracy.