IP Multimedia Subsystem - PSTN to IMS Call

This call flow covers the handling of a CS network originated call with ISUP. In the diagram the MGCF requests seizure of the IM CN subsystem side termination and CS network side bearer termination. When the MGCF receives an answer indication, it requests the IM-MGW to both-way through-connect the terminations. Originating and terminating end initiated call releases are also covered.

The following call flows analyze the PSTN to IMS call flow from different points of view:

• PSTN to IMS Call Flow
• PSTN to IMS Call Flow Poster (11x17)
• PSTN to IMS Call Overview
• High Level Flow (PSTN-IMS-Called UE)
• High Level Flow (With CSCF Details)
• IM-MGW Call Flow
• IM-MGW Context Diagram
• MGCF Call Flow
• MGCF Context Diagram
• I-CSCF Call Flow
• I-CSCF Collaboration Diagram
• Terminating S-CSCF Call Flow
• Terminating S-CSCF Context Diagram