Research Design And Implementation Of Call Session Control Function In IP Multimedia Subsystem

The key feature of IP-based Next Generation Network(NGN) is being open and convergence. The IP Multimedia Subsystem which adopts a layered open architecture realizes features of access independence, unified session and user data control, open and unified service platform, etc., which makes IMS not only a unique service control platform for converging into All-IP network, but also the foundation to realize FMC(Fixed-Mobile Convergence)and the convergence of Telecom and Internet. IMS has been considered as the heart of NGN, through which, convergence from services, equiments to network can be truely realized.CSCF (Call Session Control Function) is the core functional entity of IMS which implements the function of session control and management. CSCF realizes IMS's key idea of independence between service and control layer and separation of control and underlying transport layer,which makes the research, design and implementation of CSCF very significant to the development of IMS.In this paper, research on IMS follows the sequence of why IMS, what is IMS, how to realize IMS and how to develop IMS.The paper starts with the introduction of the background of IMS, including the analysis of the emerging of IMS, key concepts of IMS and important ideas of the IMS architecture.In the second part, key protocols of IMS are introduced, including how these Internet protocols work and IMS'requirements on these protocols, which helps to understand the reason why IMS is the key to realize the convergence of mobile network and the Internet.In the third part, the IMS software system is introduced, and the analysis of functional reqirements of IMS's core entity-CSCF is conducted.The forth part presents how to design a general framework of CSCF based on TAPA (Trillium Advanced Portable Architechture) ,and describes functions of each module and the idea of its design in detail.The fifth part is the key part of this paper, which comprehensively describes the design and implementation of a real S-CSCF entity based on the framework introduced in the last part.The design priciple and implementation method of each module are presented very clearly, the collaboration of all the key modules to realize S-CSCF's core function is also described. At last, results of a live test of S-CSCF entity is presented.The sixth part is the summary of this paper, which concludes all the achivements of the research and lists some of the points that need to be considered to further develop IMS.