Sidelink Synchronization Update for Coverage Source Switching

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Solution Overview

Problem

Existing sidelink synchronization systems fail to provide a smooth transition when a synchronization source changes from out-of-coverage to in-coverage, leading to communication interruptions and increased complexity for receiving UEs.

Innovation Solution

A method where a synchronization source UE indicates a change in synchronization source timing and frequency offset to receiving UEs via sidelink, allowing them to update their reference frequency without extensive re-synchronization searches.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a synchronization source UE changes from out-of-coverage to in-coverage, then synchronization accuracy is improved, but communication continuity deteriorates due to interruption

Engineering Contradiction:
Improvesynchronization accuracyVSAvoidcommunication continuity
Core Design Contradiction:
Measurement precisionVSReliability

Solution Approach 1:

The source UE transmits an indication message to receiving UEs before actually switching synchronization sources. This preliminary notification allows receiving UEs to prepare for the transition, ensuring they can seamlessly follow the source UE to the new synchronization source without communication interruption, thus resolving the contradiction between improving synchronization accuracy and maintaining communication continuity

Inventive Principle:
Principle #10Preliminary action

2Reliability

If receiving UEs perform extensive re-synchronization searches when synchronization source changes, then synchronization reliability is improved, but UE complexity increases

Engineering Contradiction:
Improvesynchronization reliabilityVSAvoidUE complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The source UE provides feedback information to receiving UEs through the indication message, including details about the new synchronization source. This feedback mechanism eliminates the need for receiving UEs to perform extensive re-synchronization searches, as they already have the necessary information to directly synchronize with the new source, thus reducing UE complexity while maintaining synchronization reliability

Inventive Principle:
Principle #23Feedback

Data Source

PatentEP3909319B1Sidelink synchronization update following change of coverage situation
Publication Date: 2025.12.17 NOKIA SOLUTIONS & NETWORKS OY
  • EP3909319B1 patent drawingFigure 1
  • EP3909319B1 patent drawingFigure 2A~3
  • EP3909319B1 patent drawingFigure 4

AI summary

The example and non-limiting embodiments relate generally to synchronization and, more particularly, to a sidelink synchronization procedure. Exemplified embodiments are provided that may include determining a new synchronization source by a source user equipment, where the source user equipment is configured to provide synchronization to at least one receiving user equipment with use of a sidelink. The exemplified embodiments may further include transmitting by the source user equipment to the at least one receiving user equipment an indication that the source user equipment will update from a current synchronization source to the new synchronization source. The exemplified embodiments may further include transmitting synchronization signals and control signals from the source user equipment to the at least one receiving user equipment using an updated reference frequency corresponding to use of the new synchronization source by the source user equipment.