Granular Packet Network Timing Recovery via Offset Measurement

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Solution Overview

Problem

Existing clock synchronization methods in packet networks, such as NTP and IEEE-1588, face precision limitations due to time granular switching components, which restrict the accuracy of timing information exchange between source and destination nodes.

Innovation Solution

A method called Reference-Granularity (RG) clock distribution, where timing packets are exchanged between master and slave nodes, with timestamps measured at distinct multiples of an underlying time grid, allowing for precise synchronization by determining and adjusting the frequency offset of the slave clock using the measured time grid offset.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If CTT method is used for clock synchronization, then clock frequency can be synchronized between master and slave nodes, but precision is limited by network timing granularity

Engineering Contradiction:

Improvetiming precisionVSAvoidnetwork timing granularity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent introduces an intermediary time reference signal that both master and slave nodes use to measure their respective time grid offsets. This intermediary reference allows precise measurement of granularity effects without requiring direct comparison between unsynchronized clocks, thereby achieving high precision timing measurement despite network timing granularity limitations.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the traditional mechanical clock synchronization approach (adjusting slave clock frequency based on transit time) with a computational method that calculates time grid offset using timestamp analysis. This substitution eliminates the precision limitations imposed by network timing granularity while maintaining synchronization functionality.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If timing packets are queued at switching components, then packet routing is enabled, but transit time measurement precision deteriorates

Engineering Contradiction:

Improvepacket routingVSAvoidtransit time precision

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent extracts and separately measures the time grid offset component from the total transit time variation. By isolating the granularity-induced offset using the intermediary reference method, the system can compensate for its effect, allowing standard packet routing operations to proceed while maintaining high precision timing measurement.

Inventive Principle:

Principle #2Taking out (Extraction)

3Productivity

If high timing granularity is used in switching components, then discrete time intervals are established for packet forwarding, but achievable timing precision is reduced

Engineering Contradiction:

Improvepacket forwarding efficiencyVSAvoidtiming precision

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent implements a feedback mechanism where the measured time grid offset is used to adjust the slave node's timestamping or to compensate in the synchronization calculation. This feedback loop continuously corrects for the precision loss introduced by discrete time intervals in switching components, maintaining high timing precision despite coarse packet forwarding granularity.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS7738501B2Method of recovering timing over a granular packet network

Publication Date: 2010.06.15 ZARLINK SEMICONDUCTOR INC

AI summary

A method is disclosed for recovering timing information between master and slave nodes interconnected over a packet network having an underlying time grid with a distinct granularity. A series timing packets are exchanged between said master and slave nodes to measure the time offset of the time grid relative to clocks at the master and slave clocks. This offset is then used to either adjust the local clock at the slave node, or generate the clock using a digital controlled oscillator.