5G AMF SMF Handover Session Relocation

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Solution Overview

Problem

The existing 5G system standards do not adequately address the relocation of Session Management Function (SMF) and User Plane Function (UPF) during network changes, leading to issues with maintaining continuous PDU sessions and proper resource management.

Innovation Solution

The proposed solution involves a series of message exchanges and actions between Access and Mobility Management Functions (AMFs) and Session Management Functions (SMFs) to manage the relocation of SMF and UPF, ensuring seamless handovers and updates of PDU session information, including updating IP addresses and tunnel information, to maintain service continuity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If SMF and UPF relocation is not managed during network changes, then existing 5G system standards are simpler to implement, but PDU session continuity cannot be maintained and resource management fails

Engineering Contradiction:

ImprovePDU session continuityVSAvoidhandover management complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The source AMF performs preliminary actions by selecting a target SMF and initiating the relocation process before the actual handover occurs. The Nsmf_PDUSession_UpdateSMContext request is sent in advance to update the PDU session context, ensuring that target network functions are ready before the wireless device completes its handover, thus maintaining session continuity without adding complex real-time coordination mechanisms

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The source AMF acts as an intermediary between the wireless device and the target SMF/UPF during handover. It manages the relocation by coordinating updates to PDU session contexts, tunnel information, and IP addresses through standardized interface messages, thereby simplifying the overall system complexity while ensuring reliable session continuity

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If SMF and UPF relocation is not managed during network changes, then network operation speed is faster, but service interruption occurs during handovers

Engineering Contradiction:

Improveservice continuityVSAvoidhandover time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

PDU session context updates are performed preliminarily by the source AMF before the handover completes. The target SMF is selected and contacted in advance to establish forwarding rules and tunnel information, ensuring that service continuity is maintained without requiring time-consuming real-time coordination during the actual handover execution

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent ensures continuity of useful action by maintaining PDU session contexts and data forwarding paths during the handover transition. The source SMF continues to forward data to the target SMF, and the UPF maintains active tunnels, ensuring that data transmission and service delivery continue uninterrupted throughout the handover process

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS11606727B2Handover of a wireless device in a network

Publication Date: 2023.03.14 HONDA MOTOR CO LTD

AI summary

A target access and mobility management function (AMF) receives, from a source AMF, a first message for a handover of a wireless device. A second message requesting creation of at least one first session for the wireless device is sent to a target session management function (SMF). A third message confirming creation of the at least one first session is received from the target SMF. Based on the third message, a fourth message causing release of at least one second session for the wireless device is sent to the source AMF.