Deriving IMPI from IMPU for Legacy IMS Registration

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Solution Overview

Problem

Legacy terminals in IP Multimedia Subsystem (IMS) networks are unable to share Public User Identities (IMPU) across Private User Identities (IMPI) due to their inability to provide an IMPI, which prevents effective IMS registration and service access, especially in Fixed-Mobile Convergence scenarios.

Innovation Solution

Assigning a default IMPI to subscriptions within the Home Subscriber Server (HSS) allows the IMS network to handle SIP REGISTER messages without an IMPI, enabling IMPU sharing by deriving an IMPI from the IMPU and using it for authentication and authorization checks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If legacy terminals register with IMS network, then service access is enabled, but IMPU sharing across multiple IMPIs cannot be achieved

Engineering Contradiction:

ImproveIMPU sharing capabilityVSAvoidterminal capability requirements

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The HSS acts as an intermediary that stores the mapping relationship between IMPU and multiple IMPIs. When a legacy terminal registers with only an IMPU, the HSS retrieves the associated IMPI(s) and completes the authentication process, enabling IMPU sharing without requiring the terminal to have multiple IMPIs.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system creates a virtual representation of the IMPU-IMPI relationship in the HSS database. The HSS stores multiple IMPIs associated with a single IMPU, allowing the network to handle IMPU sharing scenarios where the terminal only provides the IMPU, and the network side reconstructs the full identity mapping.

Inventive Principle:

Principle #26Copying

2Productivity

If IMPU sharing is implemented, then service usage and operator revenue increase, but authentication and authorization complexity increases

Engineering Contradiction:

Improveservice usageVSAvoidauthentication complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The HSS automatically performs the complex task of resolving IMPU to multiple IMPIs and managing authentication sessions without requiring manual intervention or complex terminal-side logic. The system self-manages the identity mapping and authentication state, simplifying the terminal requirements while enabling IMPU sharing.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The HSS pre-stores the mapping relationships between IMPU and multiple IMPIs in its database before registration occurs. This preliminary configuration allows the authentication process to proceed efficiently by simply retrieving the pre-stored mapping rather than performing complex real-time resolution.

Inventive Principle:

Principle #10Preliminary action

3Ease of operation

If derived IMPI is used for legacy terminals, then registration is enabled, but the derived IMPI may not be associated with the correct subscription

Engineering Contradiction:

Improveregistration processVSAvoidsubscription association accuracy

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The HSS uses the IMPU provided by the legacy terminal as a feedback key to query its database and retrieve the correct associated IMPI(s). This feedback mechanism ensures that even though the terminal only provides IMPU, the HSS can accurately determine the correct subscription and associated IMPI through the IMPU-IMPI mapping stored in its database.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The HSS pre-configures the correct IMPU-IMPI associations in its database during network setup. This preliminary action ensures that when a legacy terminal registers with an IMPU, the HSS can reliably retrieve the correct IMPI without risk of mismatch, as the association was pre-validated during configuration.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS8788678B2IP multimedia subsystem user identity handling

Publication Date: 2014.07.22 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A method of handling IP Multimedia Public Identity registration within an IP Multimedia Subsystem network. The method comprises receiving at a Call Session Control Function a SIP REGISTER message including a completed IP Multimedia Public Identity Attribute-Value-Pair and no IP Multimedia Private Identity. The method further comprises deriving at the Call Session Control Function an IP Multimedia Private Identity using the IP Multimedia Public Identity and sending a Cx query from the Call Session Control Function to a Home Subscriber Server, the query including the IP Multimedia Public Identity and the derived IP Multimedia Private Identity. The Home Subscriber Server identifies a subsubscription using the IP Multimedia Public Identity, and determines that the derived IP Multimedia Private Identity is not associated with said subscription. The HSS the identifies a default IP Multimedia Private Identity associated with subscription associated with said subscription, and returns a Cx response to said Call Session Control Function including said default IP Multimedia Private Identity. The Call Session Control Function uses the received, default IP Multimedia Private Identity to further handle said SIP message.