Synchronization Master Reference Path Selection

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Solution Overview

Problem

Communication networks face challenges in achieving accurate time and phase synchronization for access network nodes, particularly due to variance in send, access, propagation, and receive times, which affects the coverage area of wireless communication devices and limits the distance between radio base stations.

Innovation Solution

Implementing a synchronization module that determines and selects the most appropriate Synchronization Master reference paths using a Path Computation Engine (PCE) and synchronisation characteristics like time delay, jitter, and asymmetry values to reduce synchronization inaccuracy between access network nodes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If PTP messages are distributed from a centralized Grandmaster entity through multiple hops, then synchronization coverage can be extended to more access network nodes, but synchronization precision deteriorates due to accumulated variance in send time, access time, propagation time, and receive time

Engineering Contradiction:
Improvesynchronization coverage areaVSAvoidsynchronization precision
Core Design Contradiction:
Area of stationary objectVSMeasurement precision

Solution Approach 1:

The network is divided into multiple synchronization domains, each with its own Boundary Clock that acts as a local synchronization reference. This segmentation allows each domain to maintain high synchronization precision independently while collectively covering a larger area through the hierarchy of Boundary Clocks.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Boundary Clocks serve as intermediary devices between the Grandmaster Clock and access network nodes. These intermediaries perform local time stamping and compensation operations, preventing the accumulation of synchronization errors over multiple hops and maintaining precision across extended coverage areas.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If multiple paths are provided for Synchronization Master references to access network nodes, then synchronization reliability is improved through path selection, but device complexity increases due to path computation and selection mechanisms

Engineering Contradiction:
Improvesynchronization reliabilityVSAvoidpath computation complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The Path Computation Element performs path computation in advance before synchronization is needed. Multiple candidate paths are pre-calculated and stored, allowing the Boundary Clock to quickly select the optimal path without real-time computation, thus improving reliability while minimizing operational complexity.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The system implements feedback mechanisms where synchronization performance metrics are continuously monitored and used to update path selections. This feedback loop enables the system to adapt to changing network conditions and maintain high reliability without requiring complex manual intervention.

Inventive Principle:
Principle #23Feedback

Data Source

PatentEP3235310B1Communication network nodes and methods performed therein
Publication Date: 2021.11.03 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
  • EP3235310B1 patent drawingFigure 1
  • EP3235310B1 patent drawingFigure 2
  • EP3235310B1 patent drawingFigure 3

AI summary

Methods and modules for determining paths of Synchronisation Master references. A synchronisation module is associated with a network node of a communication network which comprises at least one Synchronisation Master entity. The synchronisation module has knowledge of a plurality of Synchronisation Master references. Endpoints of paths of the plurality of Synchronisation Master references are obtained 500. Each one of the paths extends between one of the at least one Synchronisation Master Entities and the first access network node or the second access network node. The paths are obtained 502 from a synchronisation report module associated with a network node based on the obtained endpoints. For each of the Synchronisation Master references: a first path and a second path of the obtained paths are selected 504, 506. A time synchronisation inaccuracy value between the first access network node and the second access network node is calculated 508 based on the selected first paths. Finally, a Synchronisation Master reference is selected based on the calculated 508 time synchronisation inaccuracy values, and the first access network node and the second access network node are notified 512 which Synchronisation Master reference that was selected. By arranging functionality in a communication network for determining paths along which Synchronisation Master references propagate, the Synchronisation Master references which currently provides the most appropriate synchronisation for two access network nodes may be determined and utilised by the access network nodes when serving wireless communication devices.