Improvements on the Application Triggering Architecture for the IP Multimedia Subsystem

Initial Filter Criteria (iFC) are currently used in the IP Multimedia Subsystem (IMS) to control how services are invoked. They form the core of the current Application Triggering Architecture (ATA) and are transferred to the Serving Call Session Control Function (S-CSCF) to be executed. They are statically configured by the network operator to follow a certain order depending on the initial service request sent by an end user. The S-CSCF forwards on the SIP message repeatedly to different Application Servers (AS) in a chained manner to execute each service identified by the list of iFC. This paper aims to examine deficiencies in this approach and provides a new architecture that will allow the end user to modify and control the flow of particular services. This is done through the addition of a Context Server (CS), a Service Capability Interaction Manager (SCIM), a User Service Policy Server (USPS) as well as a Service Repository Server (SRS). The modifications increase the flexibility of the architecture, allowing contextual decision to be made as well as allowing the end user to customise their service usage. This results in previously impossible use case scenarios completing successfully.