Sidelink UE Group Handover Synchronization Across Neighbor Cells

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Solution Overview

Problem

In scenarios where a group of UEs using a sidelink channel move together, such as in a geo-fencing system, the handover process for individual UEs can be asynchronous, leading to a prolonged loss of the sidelink channel, which disrupts applications relying on this communication.

Innovation Solution

A method where a first UE detects a handover event and transmits a message to other UEs in the group, triggering them to initiate handovers simultaneously, ensuring all UEs within the group hand over to a neighbor cell at the same time, thereby minimizing the disruption of the sidelink channel.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If legacy handover procedure is used for each UE independently, then each UE can be handed over individually to the neighbor cell, but the sidelink channel is lost between UEs due to asynchronous handover timing

Engineering Contradiction:

Improvesidelink channel continuityVSAvoidhandover time gap

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The first UE performs preliminary action by detecting the handover event and transmitting a handover event message to the second UE before actually executing the handover. This allows the second UE to be prepared for handover in advance, ensuring both UEs are handed over simultaneously and the sidelink channel remains continuous.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The first UE provides feedback to the second UE through the handover event message, which contains information about the handover event. This feedback mechanism enables the second UE to synchronize its handover timing with the first UE, preventing sidelink channel loss.

Inventive Principle:

Principle #23Feedback

2Device complexity

If handover is triggered for each UE independently, then the network can manage handover simply, but the sidelink channel disruption extends over a longer period

Engineering Contradiction:

Improvehandover management complexityVSAvoidsidelink channel loss duration

Core Design Contradiction:

Device complexityVSDuration of action of moving object

Solution Approach 1:

The patent merges the handover management process for multiple UEs by having them share handover event information. The first UE's handover event message is transmitted to the second UE, combining their individual handover actions into a coordinated simultaneous handover, thereby reducing the duration of sidelink channel loss.

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If coordinated handover is implemented between UEs, then simultaneous handover can be achieved, but additional messaging and coordination mechanisms are required

Engineering Contradiction:

Improvesidelink channel continuityVSAvoidhandover coordination complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The UEs perform self-service by autonomously detecting handover events and transmitting handover event messages to each other without requiring complex network coordination. The first UE detects the handover event and automatically transmits the message to the second UE, enabling coordinated handover with minimal network involvement.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS12621725B2Coordinated handover

Publication Date: 2026.05.05 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A method for coordinated handover in a system comprising a first UE (101) communicating with a second UE (102) using a sidelink channel, wherein both the first UE and the second UE are being served by a source cell (104). The method includes the first UE detecting (s402) a handover event indicating that the first UE should trigger the source cell to initiate a handover of the first UE from the source cell to a neighbor cell. The method further includes, as a result of the first UE detecting the handover event, the first UE transmitting (s404) to the second UE a handover event message indicating that the first UE has detected the handover event.