SMF Selection for PDU Session Continuity in 5G PLMN
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Solution Overview
Problem
In 5G communication systems, PDU sessions can be interrupted when a user equipment (UE) moves out of the serving area of the current SMF, especially when the Home Routed PDU Session feature does not support Deployments Topologies with Specific Session Management Function (SMF) Service Areas (DTSSA), leading to inability to update the Home SMF with new SM Context information for continued service.
Innovation Solution
A method where a first network function determines if the initial SMF supports insertion/change of a second SMF and, if not, sends a query request to a second network function to discover and preconfigure a target SMF that can serve the whole Public Land Mobile Network (PLMN), ensuring continuous PDU session service during UE mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Home Routed PDU Session feature does not support DTSSA, then the initial SMF cannot be updated with new SM Context information when UE moves out of serving area, but maintaining session continuity requires updating the SMF with new location information
Solution Approach 1:
The patent performs preliminary action by discovering and pre-configuring a target SMF that can serve the whole PLMN before the UE actually moves out of the initial SMF's serving area. The AMF determines whether the initial SMF supports DTSSA, and if not, proactively discovers a target SMF capable of serving the entire PLMN. This advance preparation ensures that when UE mobility occurs, the session can be seamlessly transferred without interruption, resolving the contradiction between maintaining session continuity and adapting to different service area requirements.
2Ease of operation
If the initial SMF is selected without considering whole-PLMN service capability, then session management is simpler initially, but session interruption occurs when UE moves out of serving area
Solution Approach 1:
The patent introduces an intermediary mechanism where the AMF acts as a mediator between the initial SMF and a potential target SMF. The AMF determines whether the initial SMF supports DTSSA and, if not, discovers a target SMF capable of serving the whole PLMN. This intermediary process ensures that the initial session establishment remains simple while preparing for future mobility scenarios, thus resolving the contradiction between ease of initial operation and reliability during mobility.
3Reliability
If a query mechanism is introduced to discover SMF capabilities, then session continuity can be maintained, but the complexity of session establishment procedure increases
Solution Approach 1:
The patent applies preliminary action by performing the SMF capability query and target SMF discovery only when necessary - specifically when the initial SMF does not support DTSSA. The AMF determines the initial SMF's capability and conditionally triggers the discovery procedure. This approach maintains session continuity while minimizing procedure complexity by avoiding unnecessary queries in cases where the initial SMF already supports whole-PLMN service.
Solution Approach 2:
The patent changes the parameter of SMF selection criteria based on the determined capability of the initial SMF. If the initial SMF supports DTSSA, the normal local selection process is used. If not, the selection criteria change to discover a target SMF capable of serving the whole PLMN. This parameter change approach resolves the contradiction by adapting the procedure complexity to the actual network configuration and capability requirements.
Data Source
AI summary
Methods and apparatuses for establishment of protocol data unit (PDU) session are disclosed. A first network function determines whether a first session management function (SMF) for a PDU session to be established for a terminal device supports insertion/change of a second SMF. When determining that the first SMF for the PDU session does not support insertion/change of the second SMF, the first network function sends, to a second network function, a query request for discovering at least one second SMF that can serve whole public land mobile network (PLMN) to which the first network function belongs. The first network function receives a query response from the second network function.