Disaster Roaming Access for UE During PLMN Service Failure

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Solution Overview

Problem

Existing systems lack a technical method for enabling seamless disaster recovery and emergency communication services when a primary network fails, particularly for critical services like emergency calls, due to network failures such as fires or floods, which can disrupt communication services for extended periods.

Innovation Solution

A method for disaster roaming is implemented, allowing User Equipment (UE) to connect with a secondary network operator to provide emergency services by establishing a connection with a secondary network node, such as an AMF, to ensure continuous communication services during network failures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If link failure detection is performed by exchanging routing protocol messages between end devices, then failure detection capability is provided, but device complexity and processing overhead increase significantly

Engineering Contradiction:
Improvefailure detection capabilityVSAvoiddevice complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent introduces a network controller as an intermediary component that centralizes the failure detection logic. Instead of end devices exchanging routing protocol messages directly, the network controller receives link status notifications from network elements and manages failure detection centrally, thereby reducing device complexity while maintaining reliability

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent extracts the failure detection function from end devices and relocates it to a dedicated network controller. This separation removes the complex failure detection processing from end devices, reducing their complexity while preserving the detection capability through the network controller's centralized management

Inventive Principle:
Principle #2Taking out (Extraction)

2Speed

If fast Reroute (FRR) is implemented with pre-configured backup paths, then traffic restoration speed is improved, but network configuration complexity and resource overhead increase

Engineering Contradiction:
Improvetraffic restoration speedVSAvoidnetwork configuration complexity
Core Design Contradiction:
SpeedVSDevice complexity

Solution Approach 1:

The patent implements pre-computation of backup paths by the network controller before failures occur. The controller proactively calculates and prepares alternative routes based on current network topology, so when a failure occurs, traffic can be switched immediately without complex real-time calculations, achieving fast restoration while simplifying configuration

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent establishes a feedback mechanism where the network controller continuously monitors link status through notifications from network elements. This real-time feedback enables the controller to dynamically adjust and recompute backup paths as needed, maintaining optimal restoration speed without requiring static complex pre-configuration for all possible failure scenarios

Inventive Principle:
Principle #23Feedback

3Productivity

If centralized network control is implemented for failure management, then coordination efficiency is improved, but control system complexity increases

Engineering Contradiction:
Improvecoordination efficiencyVSAvoidcontrol system complexity
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The patent designs the network controller to perform multiple functions including failure detection, backup path computation, and traffic restoration coordination. By consolidating these diverse functions into a single universal control entity, the system achieves improved coordination efficiency without proportionally increasing overall control complexity, as the same controller handles all tasks

Inventive Principle:
Principle #6Universality (Multi-functionality)

Data Source

PatentEP3937545B1Method and user equipment for performing disaster roaming in a wireless communication system
Publication Date: 2026.04.29 LG ELECTRONICS INC
  • EP3937545B1 patent drawingFigure 1
  • EP3937545B1 patent drawingFigure 2
  • EP3937545B1 patent drawingFigure 3

AI summary

A disclosure according to the present specification provides a method of having an access by a terminal subscribing to a first public land mobile network (PLMN). The method may comprise a step of transmitting a first request message to a network node via a base station. The base station may be a base station of a second PLMN that broadcasts system information including information about the first PLMN. The method may comprise a step of receiving, from the network node, a first response message that is a response to the first request message. The first response message may include information indicating that there is a service failure in the first PLMN. The method may comprise a step of transmitting a second request message to the second PLMN or reselecting another PLMN instead of the first PLMN, which has a service failure, on the basis of the first response message including the information.