5G SA Voice Call Fallback for IMS Registration Failure

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Solution Overview

Problem

IMS service registration failures in 5G SA networks lead to voice call service failures, as existing solutions do not adequately address the need for alternative voice call methods when IMS registration fails.

Innovation Solution

User equipment (UE) switches from a 5G SA network to an LTE network upon receiving specific identifiers in registration accept messages, enabling voice call services through VoLTE or CSFB technologies, and includes timers and user prompts for IMS activation when necessary.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If UE uses 5G SA network for voice call service, then network coverage and data transmission speed are improved, but IMS service registration may fail leading to voice call service failure

Engineering Contradiction:
Improvedata transmission speedVSAvoidvoice call service reliability
Core Design Contradiction:
SpeedVSReliability

Solution Approach 1:

The patent applies preliminary action by having the UE send an IMS registration request before attempting voice call service. The network side device responds with a registration result indication, allowing the UE to prepare in advance whether IMS service is available. This preliminary registration check prevents subsequent voice call failures and enables the UE to switch to alternative networks if needed.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary mechanism where the network side device provides a registration result indication as an intermediate signal. This indication serves as a mediator between the IMS registration status and the voice call service initiation, allowing the UE to make informed decisions about network selection and service availability without direct trial-and-error attempts.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If UE sends IMS registration request before voice call, then voice call service reliability is improved, but network signaling complexity increases

Engineering Contradiction:
Improvevoice call service reliabilityVSAvoidnetwork signaling complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the IMS registration request with the voice call service request into a single signaling interaction. The UE includes IMS registration information within the voice call setup procedure, and the network side device integrates the registration status check into the voice call processing flow. This merging eliminates separate registration signaling steps while maintaining reliability.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The patent applies universality by designing the registration result indication mechanism to serve multiple functions: it confirms IMS service availability, provides network selection guidance, and enables fallback decisions. This multi-functional approach reduces the need for separate signaling messages and simplifies the overall protocol complexity.

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

Data Source

PatentEP4329380B1Voice call method and voice call apparatus
Publication Date: 2025.11.05 VIVO MOBILE COMM CO LTD
  • EP4329380B1 patent drawingFigure 1~2
  • EP4329380B1 patent drawingFigure 3
  • EP4329380B1 patent drawingFigure 4

AI summary

The present application discloses a voice call method and a voice call apparatus, which belong to the communication field. In a case that user equipment UE accesses a first network, receiving, by the UE, a registration reception message sent by a first network side device corresponding to a first network; based on the registration reception message, in a case that a predetermined condition is met, stopping, by the UE, using the first network and connecting to a second network; and sending, by the UE, a voice call request to a second network side device corresponding to the second network, where the voice call request is used to request the second network side device to process a voice call service. The predetermined condition includes any one of the following: that the registration accept message carries a first identifier used to indicate that the UE does not support an IMS service; and that the registration accept message carries a second identifier used to indicate that the UE supports an IMS service, and the UE confirms that registration of the IMS service to the first network side device fails.