Mobile IAB Handover Handling for Idle-Inactive UEs

Solution Overview

Problem

Existing IAB-node mobility solutions fail to efficiently manage handovers for UEs in RRC_IDLE and RRC_INACTIVE states during CU changes, leading to excessive signaling overhead and potential network congestion due to simultaneous RNAU procedures.

Innovation Solution

The mobile IAB node informs UEs in RRC_IDLE and RRC_INACTIVE of an impending handover through broadcast messages or paging, providing necessary configurations and indications to transition smoothly to the target cell without triggering unnecessary cell reselection or RNAU procedures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If existing IAB-node mobility solutions are used for handover during CU changes, then handover can be performed, but excessive signaling overhead and network congestion occur due to simultaneous RNAU procedures from UEs in RRC_IDLE and RRC_INACTIVE states

Engineering Contradiction:

Improvehandover completionVSAvoidsignaling overhead

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The mobile IAB node performs preliminary actions by broadcasting handover indication messages to UEs in RRC_IDLE and RRC_INACTIVE states before the actual handover occurs. This advance notification allows these UEs to prepare for handover without simultaneously initiating RNAU procedures, thereby reducing signaling overhead while ensuring reliable handover completion.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If existing IAB-node mobility solutions are used for handover during CU changes, then handover can be performed, but network congestion occurs due to simultaneous RNAU procedures

Engineering Contradiction:

Improvehandover completionVSAvoidnetwork stability

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The mobile IAB node performs preliminary actions by broadcasting handover indication messages to UEs in RRC_IDLE and RRC_INACTIVE states before the actual handover occurs. This advance notification allows these UEs to prepare for handover without simultaneously initiating RNAU procedures, thereby reducing signaling overhead while ensuring reliable handover completion.

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If UEs in RRC_IDLE and RRC_INACTIVE perform cell reselection during handover, then UEs can find new serving cells, but unnecessary procedures are triggered causing signaling overload

Engineering Contradiction:

ImproveUE cell finding capabilityVSAvoidsignaling overhead

Core Design Contradiction:

Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

The mobile IAB node performs preliminary actions by broadcasting handover indication messages to UEs in RRC_IDLE and RRC_INACTIVE states before the actual handover occurs. This advance notification allows these UEs to prepare for handover without simultaneously initiating RNAU procedures, thereby reducing signaling overhead while ensuring reliable handover completion.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20250392971A1Handling of idle-inactive UE's during handover with mobile iab

Publication Date: 2025.12.25 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A method at a user equipment, UE that is served by a mobile integrated access backhaul, IAB, and which radio resource control, RRC, status is RRC_IDLE or RRC_INACTIVE includes receiving from the mobile IAB a first indication that the UEs in RRC_CONNECTED connected to the same mobile IAB are initiating or have initiated a handover procedure to a target cell. The method includes receiving a second indication about to which target cell the UEs in RRC_CONNECTED have been handed off.