CAG Subscription Registration Across Non-CAG Cells in 5GS
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Solution Overview
Problem
User Equipment (UE) with a Closed Access Group (CAG) subscription faces issues when attempting to access a Fifth Generation System (5GS) via non-CAG cells due to non-supporting Access and Mobility Management Functions (AMFs), leading to service denial and suboptimal user experience.
Innovation Solution
A method and system that determine whether an AMF supports the CAG feature, configuring the UE to leave non-supporting AMFs and connect to supporting ones, ensuring proper service access through message exchanges and NAS cause values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE attempts to access the 5GS via non-CAG cells, then the UE can connect to the network infrastructure, but the service access is denied because the AMF does not support the CAG feature
Solution Approach 1:
The system performs preliminary checking of CAG feature support by the AMF before allowing the UE to establish a service connection. The UDM determines whether the AMF supports CAG features and rejects registration requests from CAG-subscribed UEs to non-supporting AMFs, preventing service denial before it occurs.
Solution Approach 2:
The UDM acts as an intermediary between the UE and the AMF, mediating the registration process by checking CAG feature compatibility. It receives registration requests, determines AMF CAG support status, and either accepts or rejects the registration accordingly, ensuring proper matching between UE capabilities and network support.
2Productivity
If the AMF accepts registration requests from UEs with CAG subscriptions, then the registration procedure can be completed, but the UE cannot access services because the AMF lacks CAG feature support
Solution Approach 1:
The system performs preliminary verification of CAG feature compatibility during the registration phase. The UDM checks whether the AMF supports CAG features before completing registration, ensuring that only compatible UE-AMF pairs are registered. This prevents service delivery failures while maintaining efficient registration processing for valid cases.
Solution Approach 2:
The system applies preliminary anti-action by rejecting registration requests from CAG-subscribed UEs to non-CAG-supporting AMFs. This preemptive rejection prevents the harmful outcome of registering UEs that cannot access services, thereby maintaining both registration efficiency and service reliability.
3Reliability
If the UE is configured to access only CAG cells, then the UE can access services when CAG configuration is available, but the UE cannot access the network when configuration is not updated or unavailable
Solution Approach 1:
The UDM serves as an intermediary that manages the interaction between UE CAG configuration status and network access. It maintains awareness of UE CAG subscription status and AMF CAG support capabilities, enabling flexible routing of registration requests to appropriate AMFs while ensuring service access guarantees for CAG-subscribed UEs.
Solution Approach 2:
The system dynamically adapts the UE's network access behavior based on CAG configuration availability and AMF capability matching. When CAG configuration is available and matching AMFs are found, the system enforces CAG-only access; when configuration is unavailable or no matching AMFs exist, the system allows alternative access paths, providing dynamic adaptability while maintaining service reliability.
Data Source
AI summary
The present disclosure discloses method and apparatus for handling a user equipment (UE) (100) with a closed access group (CAG) subscription in a wireless network by a first network device (200). The method comprises receiving a registration request from the UE (100); and transmitting, a first message to a second network device (300), in response to receiving the registration request, wherein the first message indicates a request to register with the second network device (300) on behalf of the UE (100), and whether the first network device (200) supports CAG feature.