IAB Inter-CU Migration Using Proxy F1 Connection Retention

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Solution Overview

Problem

Existing inter-CU migration procedures in Integrated Access Backhaul (IAB) networks cause service interruptions and signaling storms due to the release and relocation of F1 connections, impacting UEs and IAB nodes served by the migrating node, as they require re-establishment or handover operations.

Innovation Solution

A proxy-based mechanism is employed for inter-CU migration, where only the RRC connection of the migrating IAB node is relocated to the target CU, while F1 connections of served IAB nodes and UEs remain at the source CU, with the target CU acting as a proxy, utilizing enhanced signaling to manage the migration process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If existing inter-CU migration procedures are used, then the IAB node can be migrated to a target CU, but service interruptions and signaling storms occur due to release and relocation of F1 connections

Engineering Contradiction:

ImproveIAB node migration capabilityVSAvoidservice continuity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent introduces a proxy mechanism where the target CU acts as an intermediary for F1 connections during migration. The source CU maintains F1 connections with served IAB nodes and UEs, while the target CU proxies these connections temporarily. This intermediary approach allows the IAB node to migrate to the target CU without forcing immediate re-establishment of F1 connections, thereby avoiding service interruptions and signaling storms while maintaining migration capability

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If F1 connections are released and relocated during migration, then the migrating IAB node can connect to the target CU, but UEs and IAB nodes served by the migrating node require re-establishment or handover operations

Engineering Contradiction:

ImproveCU migration flexibilityVSAvoidconnection re-establishment complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent implements preliminary action by establishing the proxy relationship at the target CU before the IAB node actually migrates. The target CU is pre-configured to proxy F1 connections, and the source CU is prepared to maintain connections during the transition. This preliminary setup ensures that when the IAB node migrates, no re-establishment or handover operations are needed for served UEs and IAB nodes, as the proxy mechanism is already in place to handle the transition seamlessly

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12543086B2Inter-CU migration in IAB network

Publication Date: 2026.02.03 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A source Integrated Access Backhaul, IAB, node (20) sends a handover request (110) from the source IAB node (20) to a target IAB node (30) to which a Mobile Termination, MT, (10) of an IAB node is to be migrated. The handover request (110) comprises an indication of a proxied inter donor IAB node migration of the MT (10) to the target IAB node (30). In some embodiments, according to the indication of the proxied inter donor IAB node migration, a radio resource control, RRC, connection of the IAB node is to be migrated to the target IAB node (30) but F1 connections and RRC connections of any children nodes served by the IAB node are to be kept at the source IAB node (20). In any event, the target IAB node (30) correspondingly receives the handover request (110) and sends a handover response (115) to the source IAB node (20).