Signaling Path Segmentation for Voice Call Continuity

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Solution Overview

Problem

Existing methods for single radio voice call continuity in IP Multimedia Subsystem (IMS) networks fail to maintain session continuity due to re-registration timeouts when a UE switches from the PS domain to the CS domain, leading to call interruptions.

Innovation Solution

An application layer gateway establishes a new signaling connection with an enhanced mobile switch center and notifies a service centralization and continuity application server to establish a new signaling connection, ensuring a continuous IMS session by sending IMS transfer requests and response messages to maintain a new session signaling path.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a UE switches from PS domain to CS domain for single radio voice call continuity, then voice call continuity is maintained, but the original IMS signaling connection is released due to re-registration timeout

Engineering Contradiction:

Improvevoice call continuityVSAvoidIMS signaling connection

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent segments the signaling path by introducing a new parallel signaling connection between ALG and SCC AS that operates independently from the original UE-S-CSCF signaling path. This segmentation allows the original IMS signaling connection to be released while maintaining a separate backup path for session control, resolving the contradiction between maintaining voice call continuity and preventing IMS signaling connection loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces SCC AS as an intermediary entity that mediates between ALG and the IMS core network. When UE switches domains, SCC AS receives transfer requests from ALG and maintains session state information, acting as a mediator that preserves the signaling connection even when the original UE-S-CSCF path is released due to re-registration timeout.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If ALG establishes new signaling connection during domain switching, then session continuity is maintained, but signaling path complexity increases

Engineering Contradiction:

Improvesession continuityVSAvoidsignaling path

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent makes SCC AS a universal entity that handles multiple functions: normal session control, domain switching coordination, and re-registration timeout management. By consolidating these functions in a single intermediary entity, the patent reduces overall signaling path complexity while maintaining session continuity during domain switching.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9603183B2Method and system for keeping single radio voice call continuity session alive

Publication Date: 2017.03.21 ZTE CORP

AI summary

A method and system are provided for keeping a single radio voice call continuity session alive. The method comprises, during switching of a terminal from a packet switch domain to a circuit switch domain, an application layer gateway establishing a new signaling connection with an enhanced mobile switch center after receiving a first transfer request and notifying a service centralization and continuity application server (SCC AS) to establish a new signaling connection with the application layer gateway, and the SCC AS establishing a new signaling connection with the application layer gateway according to the notification. Using the technical scheme of the method and system provided, the problem of call interruption due to a UE being unable to perform IMS re-registration in a destination domain in a single radio voice call continuity process in the prior art is solved.