S-NSSAI Mapping for 5G/EPS Session Continuity Across PLMNs
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Solution Overview
Problem
There is a need for a method to effectively provide session continuity and interworking between the 5G system (5GS) and the evolved packet system (EPS) to support various services, particularly in scenarios involving roaming and inter-PLMN mobility, ensuring seamless service continuity for user equipment (UE) as it moves between different network slices.
Innovation Solution
The solution involves defining interworking architectures and procedures for the 5G system (5GS) and evolved packet system (EPS) to enable session continuity, including the use of single-network slice selection assistance information (S-NSSAI) to maintain protocol data unit (PDU) sessions across different public land mobile networks (PLMNs), allowing UEs to update and maintain session contexts without releasing or re-establishing sessions during handovers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If session re-establishment procedures are performed when moving between 5GS and EPS networks, then service connectivity can be restored, but service continuity is interrupted and user experience deteriorates
Solution Approach 1:
The patent applies preliminary action by establishing session continuity mechanisms in advance before handover occurs. The network pre-configures session context information and maintains PDU session states in both 5GS and EPS networks, so when handover occurs, the session can be immediately restored without interruption. This resolves the contradiction by preparing the service connectivity restoration beforehand, eliminating the service interruption time.
Solution Approach 2:
The patent implements continuity of useful action by maintaining active PDU sessions across network boundaries. The session context is preserved and transferred seamlessly between 5GS and EPS, allowing data transmission to continue without breaking the service connection. This eliminates service interruption while maintaining reliable connectivity throughout the handover process.
2Reliability
If session context is maintained across different PLMNs, then session continuity is improved, but network complexity increases due to interworking requirements
Solution Approach 1:
The patent uses the AMF (Access and Mobility Management Function) as an intermediary to handle session context management during inter-PLMN handover. The AMF in the visited PLMN interacts with the home PLMN's network functions to maintain session continuity, abstracting the complexity of interworking behind a standardized interface. This resolves the contradiction by providing session continuity through the intermediary mechanism while hiding the underlying network complexity.
Solution Approach 2:
The patent implements multi-functionality by designing the session management architecture to handle both intra-PLMN and inter-PLMN scenarios through unified procedures. The same session context maintenance mechanisms work across different network types (5GS and EPS) and different PLMNs, reducing the need for separate complex interworking solutions and simplifying the overall network architecture.
3Adaptability or versatility
If S-NSSAI mapping is performed between HPLMN and VPLMN, then session portability is improved, but information processing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-establishing S-NSSAI mapping relationships between HPLMN and VPLMN before handover occurs. The mapping information is stored and configured in advance, allowing the network to quickly resolve session identifiers during handover without performing complex real-time mapping operations. This resolves the contradiction by improving session portability through pre-configured mappings while reducing information processing complexity during actual handover.
Data Source
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AI summary
A method performed by a user equipment (UE) in a wireless communication system is provided. The method includes transmitting, to an access and mobility function (AMF), a registration request message for moving to a first public land mobile network (PLMN) from a second PLMN, receiving, from the AMF, a registration accept message including first single-network slice selection assistance information (S-NSSAI) corresponding to the first PLMN of the AMF, determining whether second S-NSSAI asscociated with a protocol data unit (PDU) session established for the UE matches to the first S-NSSAI, wherein the second S-NSSAI corresponds to the second PLMN, and locally updating the PDU session based on a result of the determining.