Relay UE Handover Without Same-Cell Remote UE Notification

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Solution Overview

Problem

The challenge in wireless communication systems is the need for efficient cell change notification to remote user equipment (UE) during a relay UE handover in a multi-path relay scenario, which can lead to unnecessary message transmission.

Innovation Solution

The relay UE establishes a PC5 radio resource control (RRC) connection with a remote UE, transmits signals to the base station, receives a handover command, and performs a handover procedure without notifying the remote UE if they are in the same cell, thereby omitting unnecessary handover notifications.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the relay UE always notifies the remote UE about handover, then the remote UE can be informed of cell changes, but unnecessary message transmission occurs when both are in the same cell

Engineering Contradiction:

Improvehandover notification reliabilityVSAvoidmessage transmission overhead

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The notification behavior is made context-dependent rather than uniform. The relay UE evaluates the specific scenario (whether remote UE is in the same cell or different cell) and applies different notification strategies accordingly, optimizing for each local condition

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Instead of always performing the full notification action, the system performs the action only when necessary (partial action). The relay UE selectively notifies the remote UE only when the handover is to a different cell, avoiding excessive notification messages

Inventive Principle:

Principle #16Partial or excessive action

2Productivity

If the relay UE omits handover notification, then message transmission is reduced, but the remote UE may not be informed of necessary cell changes

Engineering Contradiction:

Improvecommunication efficiencyVSAvoidhandover information

Core Design Contradiction:

ProductivityVSLoss of information

Solution Approach 1:

The system incorporates feedback mechanisms where the relay UE determines notification necessity based on cell identity comparison. This feedback loop ensures notifications are sent only when actually needed, preventing information loss while avoiding unnecessary transmissions

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The relay UE performs preliminary evaluation of the handover scenario before sending notifications. By checking whether the target cell is the same as the current cell in advance, the system avoids unnecessary notifications while ensuring critical handover information is transmitted

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentEP4664998A1Operating method of relay UE, which is related to handover of relay UE in multi-path relay, in wireless communication system

Publication Date: 2025.12.17 LG ELECTRONICS INC

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AI summary

According to an embodiment, an operating method related to handover (HO) of a relay user equipment (UE) in a multi-path relay, in a wireless communication system, comprises: establishing, by the relay UE, a PCS radio resource control (RRC) connection with a remote UE having a direct path with a base station; transmitting, by the relay UE to the base station, a signal transmitted by the remote UE; receiving, by the relay UE, a HO command from the base station; and performing, by the relay UE, a HO procedure on the basis of the HO command, wherein, on the basis of the relay UE performing HO to a cell of a same base station as the remote UE, the relay UE skips transmission of an HO notification to the remote UE.