Subscriber Management Node PS Connection Status Feedback

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Solution Overview

Problem

In 4G technology, mobile terminating calls over VoLTE often fail due to the inability to accurately determine whether a PS connection is active for a terminal device, leading to incorrect forwarding of calls.

Innovation Solution

A method implemented at a subscriber management node that obtains an indication from a mobility management node about the status of a PS connection for a terminal device, and sends a response to a server based on this indication to determine whether a PS access domain should be used for a terminating call.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the IMS server queries the MME for UE IMS registration state to determine whether to forward VoLTE MT call, then the call forwarding decision can be made, but the PS connection status may be inaccurate leading to call failure

Engineering Contradiction:

Improvecall success rateVSAvoidPS connection status detection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent implements a feedback mechanism where the MME continuously monitors and reports the actual PS connection status of the UE to the HSS. When the PS connection status changes (active or inactive), the MME sends a notification to the HSS, which then updates its records and informs the IMS server. This feedback loop ensures the IMS server always has accurate, real-time information about whether the UE has an active PS connection, enabling reliable call forwarding decisions.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent performs preliminary action by having the MME proactively report PS connection status changes to the HSS before the IMS server needs to make a call forwarding decision. Instead of waiting for the IMS server to query and potentially receive outdated information, the system pre-updates the HSS with current status, ensuring accurate information is available when needed.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If the system queries UE IMS registration state to determine PS access domain usage, then call routing can be decided, but the information may be outdated causing incorrect routing

Engineering Contradiction:

Improvecall routing efficiencyVSAvoidPS connection status information accuracy

Core Design Contradiction:

ProductivityVSLoss of information

Solution Approach 1:

The system establishes a feedback channel where the MME continuously monitors PS connection status and automatically notifies the HSS of any changes. This ensures the HSS maintains up-to-date information without requiring frequent re-queries, preventing information loss and ensuring accurate call routing decisions.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The MME performs self-service by autonomously monitoring its own PS connection status and proactively reporting changes to the HSS. This self-monitoring and self-reporting mechanism ensures the system maintains accurate information without external intervention or repeated querying.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS12206819B2Methods and apparatuses for implementing mobile terminating call

Publication Date: 2025.01.21 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

Methods and apparatuses are disclosed for implementing mobile terminating call. According to an embodiment, a subscriber management node obtains, from a mobility management node, an indication that indicates whether a packet switching (PS) connection is currently active for a terminal device. The subscriber management node receives, from a server, a first query about whether a PS access domain is to be used for a terminating call to the terminal device. The subscriber management node sends a response to the server based on the obtained indication.