AMF 5GMM STATUS Message for SMF Selection Failure
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Solution Overview
Problem
The current 3GPP TR 24.890 specification does not specify how the Access and Mobility Management Function (AMF) informs the User Equipment (UE) about the failure to select a Session Management Function (SMF) for 5G Session Management (5GSM) messages, leading to potential multiple retransmissions and inefficiencies in the SM message delivery process.
Innovation Solution
The AMF creates a status message, such as a 5GMM STATUS message, containing the transport message and an indication of failure to select a SMF, which is then transmitted to the UE, allowing the UE to stop retransmissions and consider the session management transaction as unsuccessfully completed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the AMF fails to select a SMF for a received UL SM MESSAGE TRANSPORT message, then the current specification does not specify how to inform the UE, leading to potential multiple retransmissions, but this creates inefficiency and wastes time
Solution Approach 1:
The AMF sends a 5GMM STATUS message back to the UE as feedback, indicating that the SM message could not be forwarded to a SMF. This feedback mechanism allows the UE to understand the failure condition and stop retransmitting the same message, thereby eliminating time loss while maintaining reliable delivery information.
Solution Approach 2:
The AMF performs preliminary action by selecting a SMF before forwarding the SM message. When this selection fails, the AMF immediately notifies the UE via 5GMM STATUS message, preventing the UE from engaging in unnecessary retransmission cycles. This preliminary failure detection and notification approach eliminates time waste.
2Device complexity
If the AMF does not specify how to inform the UE about SMF selection failure, then the protocol remains simple, but the UE cannot properly handle the failure leading to inefficient retransmissions
Solution Approach 1:
The 5GMM STATUS message serves multiple functions: it notifies the UE of SMF selection failure, provides feedback on the received UL SM MESSAGE TRANSPORT message, and enables the UE to stop retransmissions. This multi-functional approach improves efficiency without significantly increasing protocol complexity, as it builds upon existing message structures.
3Ease of operation
If the UE continuously retransmits the SM message without receiving failure indication, then the UE follows simple retransmission logic, but this causes unnecessary retransmissions and reduces system efficiency
Solution Approach 1:
The AMF provides feedback to the UE through the 5GMM STATUS message, clearly indicating that the SM message could not be forwarded to a SMF. This feedback enables the UE to stop retransmitting the same message, thereby reducing energy consumption while maintaining simple retransmission logic for successful deliveries.
Solution Approach 2:
The failure condition, which initially causes harmful repeated retransmissions, is converted into a beneficial situation where the UE receives clear failure indication and can stop retransmitting. The 5GMM STATUS message transforms the harmful continuous retransmission behavior into a single successful delivery attempt with proper failure notification.
Data Source
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AI summary
Embodiments herein relate to a wireless device and an Access and Mobility Management Function, AMF, and methods performed by a wireless device and an AMF, respectively.