UE Roaming Slice Mapping for Allowed NSSAI Control
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Solution Overview
Problem
The challenge of managing the number of User Equipment (UEs) allowed for each network slice in the 5G System (5GS) is not clearly addressed, particularly during roaming scenarios, where network slice selection assistance information management is unclear.
Innovation Solution
The UE receives Single Network Slice Selection Assistance Information (S-NSSAI) included in rejected Network Slice Selection Assistance Information (NSSAI) and stores mapped S-NSSAIs, removing them from the allowed NSSAI when they are part of an Extended rejected NSSAI, thus managing UE access to slices effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the UE stores mapped S-NSSAIs in the storage unit during roaming, then the network slice selection accuracy is improved, but the device complexity increases due to additional storage and management operations
Solution Approach 1:
The UE performs preliminary actions by storing mapped S-NSSAIs in the storage unit before actual network slice selection is needed. This advance preparation ensures that when roaming occurs, the UE already has the necessary mapping information ready, improving slice selection accuracy without adding complexity during the critical roaming operation.
Solution Approach 2:
The mapped S-NSSAIs act as an intermediary between the home network's allowed NSSAI and the visited network's slice requirements. By introducing this intermediate mapping layer, the UE can accurately translate network slice identifiers across different networks, resolving the contradiction between selection accuracy and device complexity.
2Reliability
If the UE removes S-NSSAI from allowed NSSAI when included in Extended rejected NSSAI IE, then the reliability of network slice management is improved, but the loss of information increases as valid slice information is discarded
Solution Approach 1:
The UE extracts and removes only those S-NSSAIs from the allowed NSSAI that are explicitly included in the Extended rejected NSSAI IE received from the network. This selective extraction ensures that only genuinely rejected slices are removed, maintaining reliability by preventing use of invalid slices while minimizing information loss by preserving all other valid slice information.
Solution Approach 2:
The network provides feedback through the Extended rejected NSSAI IE indicating which S-NSSAIs should be rejected. The UE uses this feedback mechanism to reliably update its allowed NSSAI, ensuring that slice management decisions are based on explicit network instructions rather than UE assumptions, thereby improving reliability while maintaining information integrity.
Data Source
AI summary
A User Equipment (UE) includes a transmission and/or reception unit and a storage unit. During roaming, in a case that the transmission and/or reception unit receives Single Network Slice Selection Assistance Information (S-NSSAI) included in rejected Network Slice Selection Assistance Information (NSSAI) included in an Extended rejected NSSAI IE, one or more mapped S-NSSAI for the S-NSSAI included in allowed NSSAI are stored in the storage unit, and the Extended rejected NSSAI IE includes all of the one or more mapped S-NSSAI, the S-NSSAI is removed from the allowed NSSAI stored in the storage unit, and the rejected NSSAI is rejected NSSAI with respect to a current Public land mobile network (PLMN) or Stand-alone Non-Public Network (SNPN) or rejected NSSAI with respect to a current registration area.