IMS Registration Timer Management for Service Continuity

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Solution Overview

Problem

In mobile communication networks, there is a risk of registration expiration for mobile terminals in IP Multimedia Subsystem (IMS) networks when handovers occur between access networks that do not support simultaneous packet-switched (PS) and circuit-switched (CS) bearers, leading to service disruptions during call continuity transitions.

Innovation Solution

Implementing a registration timer management system where the control server updates the IMS registration timer based on control information from the switching server (MSC), ensuring continuous service by preventing registration loss and reducing the need for re-registration, even if the UE cannot refresh its PS registration status, thereby facilitating smooth transitions between CS and PS networks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the UE moves from one access network to another access network without PS bearer support, then the UE can maintain CS communication, but the IMS registration expires due to missing PS bearer support for re-registration

Engineering Contradiction:

Improveservice continuityVSAvoidregistration expiration time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The MSC sends control information to the control server before the registration timer expires, allowing the control server to proactively update the registration timer and prevent expiration. This preliminary action avoids service disruption by ensuring the UE remains registered in IMS even when moving through access networks without PS bearer support.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control server acts as an intermediary between the MSC and the IMS registration system. It receives control information from the MSC and autonomously updates the registration timer without requiring UE participation, thereby maintaining registration continuity through a mediating entity that bridges the CS and IMS domains.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If the UE cannot refresh its PS registration status during CS call sessions, then the UE maintains CS communication, but re-registration is required causing service disruption

Engineering Contradiction:

Improveseamless handoverVSAvoidregistration status

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The control server autonomously updates the registration timer based on control information from the MSC, without requiring the UE to perform re-registration actions. This self-service mechanism eliminates the need for UE participation in timer updates, ensuring seamless handover while maintaining reliable registration status.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The MSC provides feedback to the control server by sending control information about the UE's CS session status. The control server uses this feedback to determine when and how to update the registration timer, creating a closed-loop system that maintains registration reliability without disrupting UE operations.

Inventive Principle:

Principle #23Feedback

3Productivity

If the registration timer expires during ongoing CS communication, then the IMS registration is terminated, but re-registration causes service disruption and increased network traffic

Engineering Contradiction:

Improvecall continuity efficiencyVSAvoidnetwork traffic overhead

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The control server updates the registration timer in advance based on control information from the MSC, preventing expiration before it occurs. This preliminary renewal action eliminates the need for reactive re-registration procedures, thereby maintaining high call continuity efficiency while avoiding the energy waste associated with repeated registration exchanges and network traffic overhead.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9055546B2Handling a registration timer to provide service continuity in IMS

Publication Date: 2015.06.09 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

The invention relates to a method for providing service continuity with respect to a registration of a mobile terminal, UE (1), at a control server (3) of an IP Multimedia Subsystem, IMS, network, while a CS-communication session between the UE (1) and a switching server, MSC (2), of a circuit-switched, CS, network is established. The control server (3) comprises a registration timer which is used for initiating a termination of the registration of the UE (1) at the IMS network, when the registration timer expires, wherein the control server (3) updates the registration timer in dependence of a control information received (11, 24) from the MSC (2). The invention further relates to a MSC (2) providing such service.