Patent ID: 8295456

Claim:
An IMS gateway system for an IMS network, the IMS gateway system comprising: a control policy database adapted to store session control policies defining triggers for initiating charging request messages to an online charging system (OCS); a session control interface adapted to receive a session control message during an active IMS session from a serving-call session control function (S-CSCF) of the IMS network, wherein the session control message includes information on a new media for the session; a budget control system adapted to process the session control message to identify a media change during the session, to process the session control policies in the control policy database to determine whether to trigger a charging request message in response to the session control message, and to generate a charging request message for the new media for the session based on the determination; and a charging interface adapted to transmit the charging request message to the OCS, wherein the charging request message includes information on the new media for the session.