The Key Technology And Realization Policy Of The Core Control Network-Element S-CSCF Of IMS

IP Multimedia Subsystem (IMS) has attracted lots of attention since it was specified by 3 GPP. It meets both the requirements of the operators and the users, and it's a key enabler for fixed-mobile convergence.This paper will simply introduce the architecture of IMS, the function of IMS network-elements, and the representative communication flows of IMS.S-CSCF (Serving-Call Session Control Function) is the core control network-element of IMS. This paper will discuss the function division of S-CSCF. It behaves as a Registrar, performs the session control, performs service trigger, etc. We'll analyse the key technology of S-CSCF including the protocol (SIP, Diameter) S-CSCF using, the logic function S-CSCF performing (for example the service trigger, the charging).Based on the discussion, we will discuss the hardware and software requirements of S-CSCF. The focus of this paper is to bring forward a specific scheme about how to realize a S-CSCF including:The software architecture of S-CSCF including the modules division, the run-time description.The design of the modules including the function of the modules, the state-machines of some modules, and the realization policy of the modules.