UE CAG Validity Handling for Authorized 5G NPN Access
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Solution Overview
Problem
There is a need for improved handling of closed access group (CAG) validity in wireless communication systems, particularly in 5G NR, to ensure authorized access and prevent unauthorized access to non-public networks (NPNs) by UEs.
Innovation Solution
A UE maintains a CAG information list with entries including allowed CAG IDs and time validity information, allowing access to CAG cells only during authorized time periods, and performs specific actions when CAG IDs become unauthorized, such as entering limited-service states or initiating PLMN selection processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE continuously monitors CAG ID validity and performs actions when validity is no longer met, then network security is improved and unauthorized access is prevented, but device complexity and processing overhead increase
Solution Approach 1:
The UE is pre-configured with a list of authorized CAG IDs and their corresponding validity periods before accessing the network. This preliminary configuration allows the UE to autonomously determine whether it can access a CAG cell without requiring continuous network verification, thereby enhancing security while reducing real-time processing complexity.
Solution Approach 2:
The UE autonomously monitors the validity of its own CAG ID authorization based on stored validity period information and independently determines when to perform actions such as releasing connections or selecting new PLMNs. This self-service mechanism eliminates the need for continuous network-side validation, improving security through consistent enforcement while reducing device-network interaction overhead.
2Reliability
If the UE performs multiple actions when CAG validity is no longer met, then access control reliability is improved, but loss of time and service interruption increase
Solution Approach 1:
The system implements dynamic action selection based on the UE's current configuration and state. When CAG validity expires, the UE evaluates whether it is configured to perform specific actions (such as entering limited-service state, searching for suitable cells, or performing PLMN selection) and executes only the appropriate actions for its current situation. This dynamic approach ensures reliable access control while minimizing unnecessary service interruptions.
3Adaptability or versatility
If the UE strictly enforces CAG time validity and performs required actions, then network access control is improved, but device operation complexity increases
Solution Approach 1:
The system changes the operational parameters of the UE based on CAG validity status. When validity expires, the UE transitions from a normal operating state to a limited-service state, altering its behavior parameters such as allowing only emergency calls or requiring PLMN reselection. These parameter changes provide flexible access control while maintaining relatively simple device operation through automated state transitions.
Data Source
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AI summary
In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a UE. In certain configurations, the UE maintains a closed access group, CAG, information list including an entry (1110). The entry includes an allowed CAG list associated with a current PLMN. The allowed CAG list includes one or more CAG IDs. A first CAG ID is configured with a first time validity information including a first time period. The UE accesses the current PLMN via a current CAG cell supporting the first CAG ID when the first CAG ID is determined as authorized during the first time period (1120). After the first time period, the UE determines that no CAG ID supported by the current CAG cell is currently authorized (1130). The UE determines whether the UE may perform actions such as search for a suitable cell and/or applying a PLMN selection process (1140).