HSS S-CSCF Assignment Removal for IMS Failover

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

In the IP Multimedia Subsystem (IMS) network, unregistered users cannot have their Serving Call State Control Function (S-CSCF) reassigned when the currently assigned S-CSCF is unavailable, leading to service disruptions and increased operational costs due to manual administrative processes and potential HSS overload.

Innovation Solution

A method and system that monitor the availability of S-CSCFs, automatically remove the assignment of an unavailable S-CSCF, and re-select a new S-CSCF based on capability requirements, using Diameter protocol and existing IMS interfaces, allowing for automatic failover without operator intervention.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If automatic S-CSCF re-assignment is implemented for unregistered users, then service availability is improved, but system complexity increases

Engineering Contradiction:

Improveservice availabilityVSAvoidsystem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system enables automatic S-CSCF re-assignment through self-service mechanisms where the HSS autonomously detects S-CSCF unavailability and triggers re-assignment without manual administrative intervention. The HSS monitors S-CSCF status and automatically initiates the re-assignment process when failures are detected, eliminating the need for operator involvement while maintaining service availability for unregistered users.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The invention implements feedback mechanisms where the HSS continuously monitors the availability status of S-CSCFs and uses this information to trigger automatic re-assignment decisions. The system receives status information from the network about S-CSCF availability and feeds this back into the assignment management logic, enabling dynamic adaptation to changing network conditions without increasing operational complexity.

Inventive Principle:

Principle #23Feedback

2Ease of operation

If manual administrative processes are used for S-CSCF re-assignment, then operational control is maintained, but operational costs increase

Engineering Contradiction:

Improveoperational controlVSAvoidoperational costs

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The system replaces manual administrative processes with automatic self-service re-assignment mechanisms. The HSS autonomously detects S-CSCF failures and initiates re-assignment without requiring operator intervention, thereby eliminating the labor costs associated with manual processes while maintaining appropriate operational control through configurable parameters and monitoring capabilities.

Inventive Principle:

Principle #25Self-service

3Stability of the object's composition

If S-CSCF re-assignment is blocked for unregistered users, then system stability is maintained, but service continuity deteriorates

Engineering Contradiction:

Improvesystem stabilityVSAvoidservice continuity

Core Design Contradiction:

Stability of the object's compositionVSDuration of action of stationary object

Solution Approach 1:

The invention implements feedback-based re-assignment where the HSS monitors S-CSCF availability status and dynamically adjusts assignment decisions based on real-time network conditions. When S-CSCF unavailability is detected, the system automatically triggers re-assignment processes while maintaining system stability through controlled transition mechanisms and proper state management in the HSS.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system transitions from static S-CSCF assignment to dynamic re-assignment capabilities. The HSS can now adaptively change S-CSCF assignments based on real-time availability conditions, enabling the system to respond dynamically to network changes while maintaining stability through proper protocol handling and state management during transitions.

Inventive Principle:

Principle #15Dynamics

4Reliability

If frequent S-CSCF re-assignment attempts are made, then service availability is improved, but HSS overload increases

Engineering Contradiction:

Improveservice availabilityVSAvoidHSS load

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The system implements controlled re-assignment attempts rather than exhaustive or excessive actions. The HSS performs re-assignment only when necessary (upon detecting S-CSCF unavailability) and uses partial action by attempting re-assignment to alternative S-CSCFs in a controlled sequence, avoiding unnecessary processing load while ensuring service availability is restored when possible.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentEP2037658B1Assignment of a serving entity in a communication system

Publication Date: 2012.12.19 NOKIA SOLUTIONS & NETWORKS OY

Figure 1~2
Figure 3~4
Figure 5~6

AI summary

The present invention relates to assigning an S-CSCF to an un-registered user in an IMS network. A HSS maintains information about a registration state of users and about assignments of S-CSCF to the users. HSS determines if S-CSCFs are available to serve the users. When receiving a request associated with a user and requesting address of an S-CSCF assigned to the user, assignment of the S-CSCF for the user is removed from HSS if the S-CSCF has been determined not to be available and if the registration state of the user indicates that the user is not registered. The HSS may transmit Server Capabilities to an I-CSCF to enable the I-CSCF to re-select new S-CSCF to serve the user.