Design And Implementation Of IMS Charging System

At present, the telecommunication network is developed into the next generation which is based on all-IP and can provide with a wide range of services. Under this development trend, the architecture combining fixed broadband network with mobile network is expected to be implemented with IMS (IP multimedia subsystem). IMS is specified as a sub-system which supports multimedia services by 3GPP based on Release 5. IMS provides the platform for multimedia services under the IP protocol, and supports both fixed and mobile access mode. Because of its access independency, IMS is studied by standard organizations such as 3GPP to expand its capabilities, so as to provide with universal platform based on SIP (Session initiation protocol) session and to construct the common core network combining fixed network with mobile network. Along with the introduction of IMS, a lot of new services will emerge, and then the corresponging charging system becomes very important.In this thesis, the standards related to charging specified by 3GPP are studied, then after referring to the architecture including both offline and online charging defined in the standards, the function entities in that architecture is designed, involving CTF (Charging trigger function) and CDF (Charging data function). And finally, the offline and online charging function of CSCF (Call session control function) in IMS is implementated.Firstly, this thesis introduces the background of IMS and its research status both at home and abroad, including related standards and commercial experimentations. The theories related to IMS is also analyzed in detail, such as network architecture, function entities, reference points, offline and online charging architectures, related principles of charging, and etc. The function entities related to charging and the processes of offline and online charging are mainly analyzed. Secondly, the functions related to CSCF (one of the most important network entities) are designed and realized according to different charging modes, mainly including the library of CTF, the CDR (Charging data record) saving mechanism of CDF, and so on. Operations of CSCF under different charging modes and scenarios are also implementated. Finally, a test case is made to prove CSCF abilities of both offline and online charging.