Mapped S-NSSAI Registration for 5G PDU Session Transfer
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Solution Overview
Problem
In 5G network slicing, user equipment (UE) faces challenges in registering with network slices when no available Configured or Allowed NSSAI is provided, leading to difficulties in identifying suitable slices for PDU session transfer between public land mobile networks (PLMNs).
Innovation Solution
The method involves using mapped Single Network Slice Selection Assistance Information (S-NSSAI) alone for registration in a 5G system, allowing UE to indicate intended slices without relying on available S-NSSAIs in the target PLMN, utilizing a mapping between S-NSSAIs and corresponding S-NSSAIs from the home PLMN to facilitate slice selection and registration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UE uses available Configured or Allowed NSSAI for registration, then registration can be performed using standard procedures, but UE cannot register when no available Configured or Allowed NSSAI is provided
Solution Approach 1:
The network performs preliminary mapping of S-NSSAIs from the home PLMN to the visited PLMN before the UE needs to register. The AMF stores this mapping relationship and uses it to automatically translate the UE's home PLMN S-NSSAIs into appropriate visited PLMN S-NSSAIs during the registration process, eliminating the need for the UE to have pre-configured NSSAIs for the visited network.
2Ease of operation
If UE relies on available S-NSSAIs in target PLMN for slice selection, then slice selection is straightforward, but UE cannot identify suitable slices when specific S-NSSAIs are not available in the target network
Solution Approach 1:
The AMF acts as an intermediary between the UE and the visited PLMN slice resources. It receives the UE's registration request containing home PLMN S-NSSAIs, performs mapping to find corresponding visited PLMN S-NSSAIs, and transparently handles the translation without requiring the UE to directly interact with or understand the visited PLMN's specific S-NSSAI configurations.
3Productivity
If UE registers with mapped S-NSSAIs without available Configured or Allowed NSSAI, then seamless PDU session transfer is enabled, but the registration procedure becomes more complex
Solution Approach 1:
The network infrastructure (AMF) performs the mapping and translation operations autonomously without requiring additional complexity in the UE. The UE simply sends its home PLMN S-NSSAIs in the registration request, and the AMF self-services the translation to visited PLMN S-NSSAIs, maintaining simple UE operation while enabling complex cross-PLMN functionality.
Data Source
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AI summary
A method of registering to slices with mapped S-NSSAI alone in a 5GS is described. The method can include, upon a UE entering a VPLMN, the UE having a first PDN connection or a first PDU session that is to be transferred to the VPLMN and associated with a first HPLMN S-NSSAI, determining whether the UE has a first VPLMN S-NSSAI applicable in the VPLMN corresponding to the first HPLMN S-NSSAI (S910). If not, a registration request message can be transmitted to register to a slice of the VPLMN for transferring the first PDN connection or the first PDU session to the VPLMN (S920). The registration request message can include the first HPLMN S-NSSAI as a first mapped S-NSSAI for indicating the slice of the VPLMN to which the UE intends to register for transferring the first PDN connection or the first PDU session.