gNB-DU Failover for gNB-CU-UP Node Failure Resilience

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Solution Overview

Problem

The existing architecture of gNB-DU is vulnerable to service disruptions when the connected gNB-CU fails, leading to major service disruptions for users under its coverage.

Innovation Solution

A method is introduced where the gNB-DU apparatus detects failure of the gNB-CU-UP apparatus, sending a UE CONTEXT RELEASE REQUEST message to the gNB-CU-CP, which then coordinates with the AMF and SMF to re-establish RRC and DRB connections, ensuring seamless service continuity by switching to a backup gNB-CU-UP.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a gNB-DU is connected to only one gNB-CU, then the architecture is simple and easy to manage, but service disruption occurs when the connected gNB-CU fails

Engineering Contradiction:

ImprovegNB-DU connection architectureVSAvoidservice continuity

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent applies preliminary action by having the gNB-DU detect and respond to gNB-CU failure in advance, initiating the failover procedure before complete service disruption occurs. The gNB-DU monitors the connection status and automatically triggers context release and re-establishment procedures when failure is detected, preventing total service collapse.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses the gNB-CU-CP (Control Plane) as an intermediary to coordinate the failover process. When gNB-CU-UP (User Plane) fails, the gNB-CU-CP mediates between the gNB-DU and AMF/SMF to manage the context release and re-establishment, enabling seamless transition without direct gNB-DU to AMF connections.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If automatic failover procedure is implemented, then service continuity is maintained, but message processing complexity increases

Engineering Contradiction:

Improveservice continuityVSAvoidmessage processing

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the gNB-CU into separate Control Plane (gNB-CU-CP) and User Plane (gNB-CU-UP) functions. This segmentation allows the Control Plane to remain operational during User Plane failure, enabling coordinated failover without requiring complete gNB-CU shutdown. The separated functions can independently manage context release and re-establishment procedures.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS20240365432A1Method of GNB-du apparatus, method of UE and GNB-du apparatus

Publication Date: 2024.10.31 NEC CORP

AI summary

This disclosure proposes solutions for providing a resiliency of gNB-CU against possible node failures. The node failure includes unexpected system reset, system rebooting, system stall, system congestion and communication failure with neighboring nodes.A method of a gNB Distributed Unit (gNB-DU) apparatus includes detecting failure of a gNB Centralized Unit User Plane (gNB-CU-UP) apparatus. The method includes sending a UE COTEXT RELEASE REQUEST message to a gNB Centralized Unit Control Plane (gNB-CU-CP) apparatus in a case of detecting the failure of the gNB-CU-UP apparatus. The UE COTEXT RELEASE REQUEST message includes information indicating detection of the failure of the gNB-CU-UP apparatus and information indicating that Radio Resource control (RRC) connection with a User Equipment (UE) needs to be re-established. The method includes receiving a UE CONTEXT RELEASE COMMAND message from the gNB-CU-CP apparatus. The method includes sending a RRC Release message to the UE.