UE Emergency Fallback Registration Failure Handling

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Solution Overview

Problem

Current 3GPP specifications do not fully specify UE behavior for failed registration and service requests during emergency services fallback in mobile communications, particularly when the network does not accept registration or service requests.

Innovation Solution

Proposed schemes involve a UE determining failure in mobility registration or service request procedures and informing upper layers via the 5GMM protocol, which can trigger attempts for emergency calls in different domains or via different networks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If current 3GPP specifications are used for emergency services fallback, then basic emergency call functionality is supported, but UE behavior is not fully specified for failed registration or service requests

Engineering Contradiction:

Improveemergency call setup reliabilityVSAvoidUE behavior specification completeness

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent implements feedback mechanisms where the UE monitors the outcomes of registration requests and service requests during emergency services fallback. When failures occur (reject messages or transmission failures), the UE detects these conditions and triggers alternative emergency call setup procedures, ensuring reliable emergency service access despite network rejection

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent specifies preliminary UE behaviors for handling potential failures before they occur. The UE is configured to attempt emergency services fallback registration and service requests in advance, and the specification pre-defines the fallback actions to take when these attempts fail, including switching to alternative domains or networks for emergency call setup

Inventive Principle:

Principle #10Preliminary action

2Adaptability or versatility

If UE attempts emergency services fallback registration, then emergency call capability is maintained, but procedure failure may occur without defined recovery behavior

Engineering Contradiction:

Improveemergency service access flexibilityVSAvoidUE procedure complexity

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The patent segments the emergency call setup procedure into distinct phases: initial emergency services fallback registration attempt, failure detection (reject message or transmission failure), and alternative procedure selection. This segmentation allows the UE to handle each phase independently with clear, manageable actions rather than a single complex procedure

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes operational parameters based on failure conditions. When registration or service request fails, the UE modifies its behavior by switching to alternative domains (e.g., from 5G to LTE or circuit-switched domain) or different networks, effectively changing the network parameters used for emergency call setup

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12245328B2UE behavior for failed registration request or service request for emergency services fallback

Publication Date: 2025.03.04 MEDIATEK SINGAPORE PTE LTD

AI summary

Solutions pertaining to user equipment (UE) behavior for failed registration request or service request for emergency services fallback in mobile communications are proposed. An apparatus implemented in a UE determines a failure in attempting to initiate a mobility registration request procedure or a service request procedure with a network to perform an emergency service fallback. In response to the determining, the apparatus performs one or more operations including at least a UE non-access-stratum (NAS) layer in a 5th Generation Mobility Management (5GMM) protocol informing an upper layer in the 5GMM protocol of the failure to cause the upper layer to attempt an emergency call in a different domain or via a different network.