Manual CAG Cell Access Control for Subscription-Verified UE Handover

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Solution Overview

Problem

The 3GPP standard does not clearly define how a user equipment (UE) should handle manual selection of Closed Access Group (CAG) cells in the RRC_CONNECTED state when the manually selected CAG identifier is not part of the UE's subscription list, leading to potential unauthorized access in Non-Public Networks (NPNs).

Innovation Solution

Implement methods and apparatus at the base station, Access and Mobility Function (AMF), and Unified Data Management (UDM) function to manage UE access to CAG cells based on manual selection, including determining subscription information, updating allowed CAG lists, and handling over to suitable cells or maintaining RRC Inactive states.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If manual CAG selection is allowed in RRC_CONNECTED state, then user flexibility and network load balancing are improved, but security control and unauthorized access prevention deteriorate

Engineering Contradiction:

Improveuser flexibilityVSAvoidsecurity control

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The system performs preliminary CAG membership verification before allowing manual selection. The AMF checks whether the UE is allowed to access the manually selected CAG cell based on subscription information before establishing the connection, preventing unauthorized access while enabling flexible user choice.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback mechanisms where the base station and AMF continuously monitor UE access requests and provide feedback on whether the manually selected CAG is allowed. This feedback loop ensures security control is maintained while allowing manual selection when authorized.

Inventive Principle:

Principle #23Feedback

2Device complexity

If automatic CAG selection is used, then access control is simplified, but network load balancing and service optimization are limited

Engineering Contradiction:

Improveaccess control complexityVSAvoidnetwork load balancing

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The system dynamically switches between automatic and manual CAG selection modes based on network conditions and user requirements. This dynamic approach allows the network to optimize load balancing by enabling manual selection when needed while maintaining simplified automatic selection as the default, achieving both security and productivity goals.

Inventive Principle:

Principle #15Dynamics

3Ease of operation

If manual CAG selection is permitted without subscription verification, then user autonomy is improved, but unauthorized access increases

Engineering Contradiction:

Improveuser autonomyVSAvoidunauthorized access

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The AMF acts as an intermediary between the UE and the CAG cell. It receives manual selection requests from UEs, verifies subscription information, and only allows access if the UE is authorized. This intermediary function maintains user autonomy while preventing unauthorized access through centralized verification.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12470908B2Communication system

Publication Date: 2025.11.11 NEC CORP

AI summary

Methods and apparatus are disclosed for controlling whether a user equipment (UE) is allowed to access a cell of a closed access group (CAG) when the CAG is selected manually by a user of the UE.