5G UE Substate Selection for Service Area Restrictions
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Solution Overview
Problem
The existing 5GMM protocol experiences ambiguity and issues in substate selection and behavior for user equipment (UE) when service area restrictions are applied, leading to mismatches in expected UE behavior and inefficient operations in restricted service areas.
Innovation Solution
The proposed solution involves determining the substate based on whether the current tracking area is part of a non-allowed area or an allowed area, and enforcing additional actions in the 5GMM-REGISTERED.NON-ALLOWED-SERVICE substate to accurately reflect pending actions and restrictions, such as initiating mobility registration and PDU session release procedures appropriately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the existing 5GMM protocol is used for substate selection in service area restrictions, then the protocol can be maintained with minimal changes, but ambiguity and mismatches in UE behavior occur in restricted service areas
Solution Approach 1:
The service area restriction functionality is segmented into distinct substates (5GMM-REGISTERED.NORMAL-SERVICE and 5GMM-REGISTERED.RESTRICTED-SERVICE), allowing the protocol to handle different service areas with specific behaviors. This segmentation resolves ambiguity by providing clear behavioral definitions for each substate while maintaining the overall 5GMM protocol structure.
Solution Approach 2:
The protocol introduces dynamic substate transitions based on service area restrictions. The UE dynamically switches between 5GMM-REGISTERED.NORMAL-SERVICE and 5GMM-REGISTERED.RESTRICTED-SERVICE substates depending on whether the current tracking area is restricted, enabling adaptive behavior without requiring a completely new protocol framework.
2Reliability
If service area restrictions are enforced with clear substate definitions, then UE behavior mismatches are reduced, but additional substate management complexity is introduced
Solution Approach 1:
The protocol performs preliminary determination of whether the current tracking area is restricted before initiating service procedures. By evaluating service area restriction status in advance, the UE can select the appropriate substate and enforce correct behaviors proactively, preventing mismatches rather than correcting them later.
Solution Approach 2:
The protocol implements feedback mechanisms where the network provides service area restriction information to the UE, and the UE adjusts its substate selection based on this feedback. This closed-loop approach ensures reliable enforcement of service area restrictions while managing complexity through structured information exchange.
3Productivity
If ambiguous substate selection is allowed in the existing protocol, then protocol simplicity is maintained, but unnecessary signaling and redundant mobility registration updates occur
Solution Approach 1:
By segmenting the service area restriction handling into distinct substates, the protocol enables efficient decision-making. The UE can determine whether to proceed with mobility registration or other procedures based on its current substate, avoiding unnecessary signaling and redundant updates that would occur with ambiguous substate selection.
Data Source
AI summary
This disclosure describes example embodiments and techniques to resolve UE behavior for several SAR use cases. The substate selection for a UE which has a valid SAR list and is currently camped on a cell which is in the registered PLMN or a PLMN from the list of equivalent PLMNs and whose TAI is not in the list of “allowed tracking areas” or is camped on a cell whose TAI is in the list of “non-allowed tracking areas,” has gaps in functionality and certain use cases. There are conflicting requirements as to what is the substate to be chosen by the UE. Additionally, there are certain behaviors missing for a UE in substate 5GMM-REGISTERED.NON-ALLOWED-SERVICE.