SMF N4 Session Failure Handling in 5G Core
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Solution Overview
Problem
Network glitches in 5G cellular networks due to N4 interface failures lead to call failures and increased network load, as existing mechanisms do not provide a reliable failure mechanism for the N4 interface.
Innovation Solution
A mechanism is introduced where the Session Management Function (SMF) detects N4 session failures, initiates a timer for retrying the N4 session establishment, and maintains user equipment in an idle state during this time. Once the N4 session is established, the SMF brings the user equipment back to an active state, and an N3 data path is established only when the user equipment intends to send data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the SMF attempts to establish an N4 session continuously during network glitches, then the session establishment reliability is improved, but the network load increases and causes resource wastage
Solution Approach 1:
The SMF initiates a timer before actually attempting to establish the N4 session. This preliminary timing action allows the system to wait for a reasonable period before retrying, preventing immediate and continuous retry attempts that would overwhelm the network with redundant establishment requests during transient glitches.
Solution Approach 2:
The system dynamically adjusts its behavior based on the timer state. While the timer is active, the SMF maintains UE in idle state and avoids establishing N3 data paths. When the timer expires or N4 session is successfully established, the system transitions to active state. This dynamic state management prevents unnecessary network resource allocation during failure conditions.
2Adaptability or versatility
If the SMF establishes N3 data path during N4 interface failure, then data transmission capability is maintained, but network resources are wasted
Solution Approach 1:
The SMF starts a timer before attempting to establish the N4 session. This preliminary timing action allows the system to wait for a reasonable period before retrying, preventing immediate and continuous retry attempts that would overwhelm the network with redundant establishment requests during transient glitches.
Solution Approach 2:
The timer acts as an intermediary mechanism between the SMF and the N4 session establishment process. It mediates the interaction by introducing a delay period that prevents premature or redundant establishment attempts, thereby avoiding the allocation of N3 data path resources when the N4 interface is unavailable.
3Stability of the object's composition
If the SMF maintains UE in active state during N4 failure, then service continuity is improved, but network load increases
Solution Approach 1:
The system dynamically adjusts the UE state based on N4 session establishment status. When N4 failure is detected and the timer is active, the SMF transitions the UE to idle state, releasing network resources. When the timer expires or N4 session is successfully established, the system transitions back to active state. This dynamic state management prevents unnecessary network resource allocation during failure conditions while maintaining service continuity when possible.
Solution Approach 2:
The timer provides feedback to the SMF about the state of N4 session establishment. While the timer is running, it indicates that establishment is in progress or failed, prompting the SMF to maintain UE in idle state. When the timer expires or success is detected, the feedback mechanism triggers a transition to active state. This feedback loop ensures appropriate resource allocation based on actual session establishment status.
Data Source
AI summary
A method includes detecting, using a session management function (SMF) at a core network component, an N4 session failure between the SMF and a User Plane Function (UPF) at the core network component, initiating, using the SMF, a timer for establishing an N4 session between the SMF and the UPF, maintaining, using the SMF, a user equipment connected to a network in an idle state while the timer is active, attempting, using the SMF, to establish the N4 session while the timer is active, and bringing, using the SMF, the user equipment back to an active state after the N4 session is established.