AMF CAG Support Indicator for 5G Registration Loop
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Solution Overview
Problem
Conventional methods do not define the behavior of networks that support or do not support the Closed Access Group (CAG) feature when interacting with User Equipment (UE) that either supports or does not support CAG, leading to UE being stuck in a loop of registration attempts and failing to access 5G services.
Innovation Solution
The proposed solution involves the Access and Mobility Management Function (AMF) determining whether a registration request message from the UE includes a CAG support indicator, and based on this, sending appropriate 5GMM cause values to the UE, such as 5GMM cause #7, #11, or #27, to enable the UE to select alternative cells for service access without retrying non-CAG cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the AMF sends 5GMM cause #76 to the UE to indicate CAG authorization issues, then the UE is informed of the CAG-related rejection, but the UE cannot understand the cause and discards the message, leading to repeated registration attempts and service access failure
Solution Approach 1:
The patent changes the parameter of the 5GMM cause value from #76 (CAG-specific) to alternative values (#7, #11, or #27) that have general meanings understandable by all UEs. This parameter substitution resolves the information loss by ensuring the UE can comprehend the rejection reason and take appropriate actions.
2Ease of operation
If the UE repeatedly attempts registration on the same non-CAG cell after timer expiry, then the UE follows the conventional procedure, but the UE gets stuck in a loop and cannot access 5G services
Solution Approach 1:
The patent introduces feedback mechanism where the AMF provides specific cause values (#7, #11, or #27) to the UE that indicate whether alternative cells or PLMNs should be selected. This feedback prevents the UE from blindly retrying on the same cell, breaking the registration loop and reducing access delay.
Solution Approach 2:
Instead of having the UE continue retrying on the same cell (conventional approach), the patent inverts the behavior by directing the UE to select alternative cells or PLMNs based on the cause value received, thereby breaking the problematic registration loop.
3Adaptability or versatility
If the network does not define behavior for handling UEs with different CAG support capabilities, then the system maintains flexibility, but the network cannot properly differentiate between CAG-capable and non-CAG-capable UEs
Solution Approach 1:
The patent introduces a new parameter (CAG support indicator) in the registration request message that allows precise detection of UE CAG capability. This parameter addition enables the network to accurately differentiate between CAG-capable and non-CAG-capable UEs while maintaining system flexibility.
Data Source
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AI summary
A method for managing a Closed Access Group (CAG) feature using an Access and Mobility Management Function (AMF) server. The method includes receiving a registration request message from a User Equipment (UE) for registering for a CAG subscription. The method includes determining that the UE is subscribed to access the network through a CAG cell only. The method includes determining whether the registration request message includes a CAG support indicator. The method includes determining whether the UE supports the CAG feature based on the CAG support indicator. The method includes sending either a registration accept message including a CAG information list to the UE when the UE supports the CAG feature, or a registration reject message including a 5GMM cause value other than a 5GMM cause #76 to the UE when the UE does not support the CAG feature.