IP multimedia subsystem online session charging call control

An efficient IP Multimedia Subsystem (IMS) online charging system is important for operator revenue generation. However, 3rd Generation Partnership Project (3GPP) specifications do not adequately address how online session charging shall be accomplished for IMS networks, especially how IMS network elements such as the application server and the serving call session control function (S-CSCF) interact with the online charging server (OCS). To remedy the shortcoming of 3GPP online charging standards, this paper presents a policy-based IMS call control system that converges the multiple application servers and the IMS gateway functionality into one IMS node for online session charging. The IMS session charging call control system employs a session charging trigger mechanism that enables a real-time report of session information and provides budget control for online quota monitoring. It also enables service logic for multiple applications to be executed in a single node to greatly reduce traffic access between the IMS call session control function (CSCF) and the OCS.