UE Network Access Mode Control for Emergency Call Deadlock

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Solution Overview

Problem

In wireless communication, network-initiated deregistration procedures lead to abnormal cases causing UE to enter a deadlock loop during PLMN or SNPN registration, resulting in network congestion and failure to handle emergency calls due to disabled network access mode capabilities.

Innovation Solution

A method for user equipment (UE) to monitor operations and control network access mode capabilities, enabling them when disabled due to network-initiated procedures, and memorizing identities of PLMNs or SNPNs where capabilities were disabled to prevent deadlock and facilitate emergency calls.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If UE disables network access mode capability due to network-initiated deregistration procedure, then abnormal registration cases are handled, but UE gets stuck in deadlock loop and cannot perform emergency calls

Engineering Contradiction:

Improveregistration procedure reliabilityVSAvoidemergency call capability

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent introduces a timer parameter (T3502) that changes the state of network access mode capability from permanently disabled to temporarily disabled with time-based recovery. This parameter change allows the UE to automatically re-enable capability after a specified duration, breaking the deadlock loop while maintaining reliability during abnormal registration cases.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent makes the network access mode capability dynamic rather than static. The capability is temporarily suspended during abnormal deregistration procedures but can be recovered after a timer expires. This dynamic behavior allows the system to adapt between reliability requirements during abnormal cases and operational capability for emergency calls.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If UE enters PLMN-SEARCH state after deregistration, then PLMN selection is performed, but UE may repeat registration attempts in loop causing network congestion

Engineering Contradiction:

ImprovePLMN selection flexibilityVSAvoidnetwork signaling efficiency

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The patent implements preliminary action by introducing a timer (T3502) that starts when the UE enters PLMN-SEARCH state after deregistration. This timer prevents the UE from immediately attempting re-registration on the same PLMN, creating a cooling period that avoids repetitive signaling loops while still allowing PLMN selection flexibility when the timer expires.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If UE disables N1 mode capability for PLMN/SNPN selection, then abnormal deregistration cases are prevented, but emergency PDU session establishment is blocked

Engineering Contradiction:

Improvederegistration procedure stabilityVSAvoidemergency service access

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent uses timer parameter T3502 to change the duration for which N1 mode capability is disabled. After the timer expires, the capability is automatically re-enabled, allowing emergency PDU session establishment while maintaining stability during abnormal deregistration procedures. This parameter-based control resolves the contradiction between reliability and adaptability.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20240414636A1User equipment and method to forbid PLMN or SNPN and handle emergency call due to deregistration

Publication Date: 2024.12.12 MEDIATEK SINGAPORE PTE LTD

AI summary

A user equipment and a method to forbid PLMN or SNPN and handle emergency call due to deregistration are provided. The method includes: monitoring an operation of the UE; and controlling the UE to start a timer for enabling a network access mode capability for the 3GPP access when the UE disables the network access mode capability for 3GPP access due to a network initiated procedure. The UE memorizes an identity of PLMNs or SNPNs where the network access mode capability for the 3GPP access was disabled.