VLR Feedback for CSFB Call Abort in LTE Networks

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Solution Overview

Problem

In the current CSFB call mechanism, the MME cannot detect when a calling side has released a call, leading to unnecessary switches from LTE to 2G/3G, wasting network resources and degrading user experience due to invalid switches and service disruptions.

Innovation Solution

A method where the VLR judges whether a call needs to be aborted and sends an SGs message to the MME to reject the CSFB call, preventing the callee UE from switching back to the 2G/3G network by indicating a call abort through specific messages.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the MME cannot detect call release by the calling side, then the CSFB call mechanism can be maintained simple, but invalid switches occur and network resources are wasted

Engineering Contradiction:

ImproveCSFB call mechanism complexityVSAvoidnetwork resource waste

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The VLR sends a notification message to the MME to provide feedback about the call release status. This feedback mechanism allows the MME to detect when the calling side has released the call, preventing the MME from triggering unnecessary call progress and avoiding invalid switches that waste network resources.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The VLR performs preliminary action by detecting the call release and sending notification to the MME before the MME can trigger subsequent call progress. This preliminary detection and notification prevents the invalid switch from occurring in the first place.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If the MME triggers subsequent call progress after receiving extended service request, then the CSFB call flow can proceed normally, but invalid switches occur when call was already released

Engineering Contradiction:

ImproveCSFB call processing efficiencyVSAvoidcall switching reliability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The VLR provides feedback to the MME about the actual call status by sending a notification message when the calling side releases the call. This feedback ensures the MME has accurate information before triggering call progress, preventing invalid switches while maintaining normal CSFB call processing.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The VLR sends a notification message to the MME to preemptively counteract the potential invalid switch. By notifying the MME of the call release before the MME triggers call progress, the system prevents the harmful effect of invalid switching while preserving legitimate call flows.

Inventive Principle:

Principle #9Preliminary anti-action

3Ease of operation

If the MSC considers paging response message as abnormal and discards it, then the system can handle call release gracefully, but call resources are wasted due to unnecessary switching

Engineering Contradiction:

Improvecall release handlingVSAvoidcall resource waste

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The VLR sends feedback to the MME about the call release status, enabling the MME to understand why the paging response is being discarded. This feedback mechanism allows graceful handling of call release while preventing the MME from initiating unnecessary resource allocation for invalid switches.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The VLR acts as an intermediary between the MSC and MME, translating the call release status into a notification message that the MME can understand. This intermediary role enables graceful call release handling while preventing resource waste by ensuring the MME has accurate call status information.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Adaptability or versatility

If the UE switches back to LTE after invalid switch to 2G/3G, then the user can maintain data service, but network resources are wasted and user experience is degraded

Engineering Contradiction:

Improvenetwork switching adaptabilityVSAvoidnetwork resource consumption

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The VLR provides feedback to the MME about call release status, enabling the MME to prevent invalid switches before they occur. This feedback mechanism maintains network switching adaptability for legitimate calls while eliminating wasteful switches that consume unnecessary network resources.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The VLR performs preliminary detection and notification of call release to the MME before the UE can initiate an invalid switch to 2G/3G. This preliminary action prevents the invalid switch from occurring, preserving network resources while maintaining the UE's ability to switch networks for legitimate calls.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentEP2549824B1Method, device and system for aborting circuit switched fallback call

Publication Date: 2019.12.04 HUAWEI TECH CO LTD

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AI summary

Embodiments of the present invention provide a method for aborting a CSFB call, which includes: judging, by a VLR, whether a call needs to be aborted; if the call needs to be aborted, sending, to an MME, an SGs message indicating a call abort, so that the MME rejects the CSFB call. Correspondingly, the embodiments of the present invention further provide a mobility management entity, a visitor location register and a communication system.