PDU Session Handling with SCP Error Signaling During SMF Mobility
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Solution Overview
Problem
Existing 5G networks lack a clear method for handling error situations when a Service Management Function (SMF) or Intermediate SMF (I-SMF) does not serve a User Equipment (UE) due to mobility, particularly in scenarios with specific SMF service areas, leading to potential disruption of PDU sessions.
Innovation Solution
The proposed method involves generating an error indication by the SMF or AMF when a UE moves out of its service area, and transmitting a response message including this error indication via the Service Communication Proxy (SCP), which can include instructions for the SCP to avoid reselection procedures, and may involve I-SMF insertion, change, or removal processes to maintain PDU session continuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the SMF or I-SMF serves a UE in a specific service area, then the PDU session can be established and maintained, but when the UE moves out of the service area, the SMF/I-SMF cannot continue to serve the UE, leading to session disruption
Solution Approach 1:
The patent implements dynamic SMF selection based on UE mobility. When a UE moves out of the current SMF's service area, the network dynamically selects a new SMF that supports the target service area. This is achieved through mobility detection mechanisms that trigger SMF reselection, ensuring the PDU session continues with an appropriate SMF without manual intervention.
Solution Approach 2:
The patent employs feedback mechanisms where the AMF monitors UE location and service area compatibility. When the UE moves out of the current SMF's service area, the AMF receives feedback about the location change and initiates the SMF change procedure by selecting a new SMF that supports the target service area, thereby maintaining session continuity.
2Reliability
If the network performs SMF reselection when UE moves out of service area, then session continuity can be maintained, but this requires additional signaling and processing time
Solution Approach 1:
The patent implements preliminary action by pre-configuring service area information in the PDU session context during session establishment. The AMF stores the service area supported by the current SMF in the session context. When mobility occurs, this pre-stored information enables rapid detection of service area mismatch and accelerates the SMF reselection process, reducing latency.
Solution Approach 2:
The patent optimizes the SMF reselection process by skipping unnecessary discovery and selection steps. Since service area information is already available in the session context, the AMF can directly identify when an SMF change is needed and rapidly select a new SMF without performing full discovery procedures, thereby reducing the time loss during mobility events.
3Reliability
If the AMF detects UE mobility and initiates SMF change procedure, then the PDU session can be maintained with a new SMF, but this requires complex coordination between AMF, SCP, and SMF nodes
Solution Approach 1:
The patent uses the Service Communication Proxy (SCP) as an intermediary to simplify the SMF change procedure. The AMF communicates with the SCP, which in turn interacts with the SMF and NRF. This intermediary architecture abstracts the complexity of SMF reselection, providing a standardized interface for service area verification and SMF selection, thereby reducing the coordination burden on individual network functions.
4Ease of operation
If the SMF generates an error indication when UE is outside service area, then the AMF can initiate I-SMF procedure, but this requires clear error signaling and interpretation mechanisms
Solution Approach 1:
The patent uses standardized error indication signaling (analogous to color changes as visual indicators) where the SMF generates specific error indications when detecting that the UE is outside its service area. These error indications are transmitted to the AMF through the N16 interface, providing clear and unambiguous signals that trigger the appropriate I-SMF insertion or change procedures, ensuring accurate information transfer without loss.
Data Source
AI summary
The present disclosure provides a method (500) performed by a Service Management Function (SMF) for handling a Protocol Data Unit (PDU) session, comprising: generating (S501) an error indication when receiving a request message for a service operation via a service communication proxy (SCP) from an Access and Mobility Management Function (AMF) after a User Equipment (UE) establishes the PDU session with the SMF and moves from a first service area to a second service area which is different from the first service area and not supported by the SMF, the SMF being a first SMF or an intermediate SMF (1-SMF) supporting the first service area; and transmitting (S503) a response message for the service operation including the error indication to the AMF via the SCP.