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

In order to provide next generation network services, 3GPP introduce IP Multimedia Subsystem (IMS) in Release 5, along with the enhancement of telecommunication ability and diversification of telecommunication services. IMS is located in the 3G Core Network and built on Packet Domain. It chooses Session Initiation Protocol (SIP) as its signal control protocol. IMS is connected to the PSTN/ISDN and it controls the voice or multimedia call in PSTN/ISDN and Internet. IMS includes several modules, such as call session control, Home Subscriber Server (HSS), Media Gateway Control Function (MGCF), Media Gateway (MGW), Multimedia Resource Function Controller (MRFC) and so on. Call Session Control Function (CSCF) is responsible for dealing with the signal message of multimedia session. With the development of Fixed Mobile Convergence (FMC), IMS is the most important phase in Next Generation Network (NGN).The paper researches into 3GPP standards correlative with IMS. First, introduces some background knowledge of IMS, such as the development of UMTS, the architecture of IMS, function entity and reference point of IMS and so on. In order to understand the principle and process how the IMS elements implement the multimedia services, we describe the primary elements of IMS with SDL software tools, simulate the handling flow of CSCF entities in the courses of UE registration and the establishment of session, and then, validate the correctness of SDL description. We analyze the oSIP protocol stack, and extend it for IMS. Then, design the P-CSCF system and implement some parts of the system. Last, summarize the paper, point out all the misgivings in SDL description and P-CSCF system, and raise the respect for IMS research.