Session Handover for Held State Voice Calls in IMS Networks

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Solution Overview

Problem

Existing voice session transfer methods in IMS networks fail to correctly handle held state sessions, leading to incorrect call connections and user experience issues due to incorrect media state information.

Innovation Solution

A method where the SCC AS updates the remote leg using held state session state information and notifies the eMSC, ensuring the eMSC completes the call setup according to the held state, thereby correcting the session transfer process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the SCC AS uses default active state information for session transfer, then the session transfer process is simple, but the held state session is transferred incorrectly

Engineering Contradiction:

Improvesession transfer process simplicityVSAvoidheld state session transfer accuracy

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The SCC AS performs preliminary identification of the session state before executing the transfer. By checking whether the session is in held state or active state before transfer, the system prepares the correct state information in advance, ensuring accurate transfer without complicating the overall process

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback by notifying the eMSC of the correct session state (held or active) during the transfer process. This feedback mechanism ensures that the eMSC uses the correct state information for call setup, preventing incorrect transfer while maintaining process efficiency

Inventive Principle:

Principle #23Feedback

2Productivity

If the eMSC completes call setup without verifying session state, then the call setup process is fast, but the user experience deteriorates due to incorrect connections

Engineering Contradiction:

Improvecall setup speedVSAvoidcall connection accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The eMSC receives and stores the session state information (held or active) as notified by the SCC AS before initiating call setup. This preliminary action ensures that the correct state is already prepared when call setup begins, maintaining speed while ensuring accuracy

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The SCC AS provides feedback to the eMSC about the correct session state through notification messages during the transfer process. This feedback enables the eMSC to adjust its call setup procedure appropriately without significantly delaying the process

Inventive Principle:

Principle #23Feedback

Data Source

PatentEP2487958B1Method and system for realizing session handover

Publication Date: 2018.09.12 ZTE CORP

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AI summary

The present invention provides a method for realizing session transfer, comprising: a service continuity application server (SCC AS), after receiving a session transfer request, when judging that a state of a session needed to be transferred is in a held state, updating a remote leg by using a held state session state information, and notifying an enhanced mobile switching center (eMSC) that the state of the session needed to be transferred is the held state; and the eMSC completing a call setup of a target access network according to the held state. The present invention also provides a system for realizing session transfer. The present invention can realize correct transfer of a held state voice session, realize correct service logic and improve user experience.