Design And Implementation Of Ip Multimedia Subsystem S-cscf Function Entity

IP Multimedia Subsystem (IMS) has been defined as a multimedia service control structure, which is over IP bearing network, independent of access, standards-based and open, aiming at providing end-to-end users, controllable, complete QoS IP multimedia services in the wide IP environment of mobile network. The basic starting point of IMS lodged by 3GPP is to combine mobile communications network technology and Internet technology organically and to build a new future-oriented information and communication network. IMS has realized separation of control and underlying transport layer and independence between service and control layer, provided an open interface to access all the service server, and allows various service providers to provide services to the network through a standard interface.CSCF in the core control level of IMS, is the session control function modules of IMS, and is the core of the controlled entities. A major characteristic of IMS system is using SIP as a core control protocol. In the IMS system, all the user callings have to exist as session form, as defined in the SIP protocol, and CSCF realizes call control functions of IMS depending on the completion of SIP multimedia session management. S-CSCF is the core services control entity of IMS, doing services for UA,such as session control, registration and services triggering. When UA is in session , the S-CSCF needs to maintain session state, and could communicate with other entities according to the service needs. The specific functions S-CSCF achieved include : processing registration related requests, offering session control for registered users, service triggering on the ISC interface, interacting with and OAM modules, interacting with HSS through Cx interface.This thesis starts with the introduction of concepts of IMS and the composition of IMS architecture; Next, the functional reqirements of IMS's core entity-CSCF is analysed; Another the paper presents how to design a framework of S-CSCF based on TAPA; Then, to describe the implementation of a real S-CSCF entity.The design priciple and implementation method of each module are presented very clearly, and the collaboration of all the key modules to realize S-CSCF's core function is also described. At last, results of test of S-CSCF entity are presented, and the summarization of my work in the period of graduation project is introduced.