AMF Handover Handling in 5G Networks
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Solution Overview
Problem
The current 5G network specifications lack efficient handover mechanisms, particularly at the N2 reference point between the Radio Access Network (RAN) and the Access and Mobility Management Function (AMF), due to new concepts like Mobility Management-Session Management split, network slicing, and stringent latency requirements.
Innovation Solution
A method is introduced where the AMF receives handover messages, sends Protocol Data Unit (PDU) requests to the Session Management Function (SMF), activates a timer, and transmits a handover request to the Target-RAN only after receiving responses for all PDU requests, ensuring timely and optimized handover execution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the AMF waits for PDU response messages from SMF before executing handover, then handover reliability is improved, but handover execution time increases
Solution Approach 1:
The AMF starts a timer when it receives the handover required message from the RAN node, initiating the timing mechanism before the handover execution. This allows the AMF to monitor the elapsed time and make decisions about handover execution based on both response reception and time constraints, resolving the contradiction between waiting for responses and maintaining execution speed.
Solution Approach 2:
The patent introduces a time parameter (timer) that changes the handover decision criteria from purely response-based to time-constrained response-based. The AMF evaluates whether to execute handover based on both receiving PDU response messages and the elapsed time since timer activation, allowing flexible adjustment of handover timing to balance reliability and speed.
2Speed
If the AMF executes handover without waiting for all PDU response messages, then handover speed is improved, but handover reliability deteriorates
Solution Approach 1:
The patent changes the handover decision parameter from binary (wait for all responses or don't wait) to a time-constrained approach. The AMF uses the timer to determine when to execute handover based on elapsed time, allowing the system to balance between waiting for responses and maintaining speed by executing handover when time constraints are met even if not all responses are received.
3Loss of time
If the AMF uses timer-based handover execution, then latency performance is improved, but control complexity increases
Solution Approach 1:
The AMF initiates the timer at the moment it receives the handover required message, which is a clear and simple trigger point. This preliminary action establishes the timing baseline without requiring complex continuous monitoring or calculation, adding minimal control complexity while achieving latency performance improvement.
Solution Approach 2:
The AMF uses the timer as a feedback mechanism to monitor elapsed time and adjust handover execution decisions accordingly. The timer provides simple time-based feedback that allows the AMF to balance between waiting for PDU responses and executing handover timely, improving latency performance with minimal additional control complexity.
Data Source
AI summary
The embodiments herein relate to a method performed by an AMF (106) for handling handover. The AMF (106) receives one of: a handover required message and a first request message. The handover required message is received from an S-RAN (104s) and the first request message is received from another AMF (106) in response to the handover required message. The AMF (106) sends to a SMF (108), a set of one or more first request messages and activates a timer. The AMF (106) determines whether at least one of the following is true: a certain amount of time has elapsed since the timer was activated and the AMF (106) has received a first PDU response message for each one of the first PDU request messages. The AMF (106) transmits a handover request message to a T-RAN (104t) as a result of determining that at least one of the conditions is true.