Patent ID: 8139735

Claim:
An IMS gateway system for an IMS network, the IMS gateway system comprising: a session control interface adapted to exchange session control messages for an IMS session with a call session control function (CSCF) of the IMS network; a charging interface adapted to exchange charging messages with an online charging system (OCS) of the IMS network; and a control system adapted to wait for a session initiation message; responsive to receiving a session initiation message from a first subscriber through the session control interface to initiate a session with a second subscriber, the control system is adapted to transmit an initial credit control request message through the charging interface to the OCS to initiate a charging session for the first subscriber with the OCS, and wait for an initial credit control answer message from the OCS; responsive to receiving the initial credit control answer message from the OCS through the charging interface, the control system is adapted to transmit the session initiation message to the second subscriber through the session control interface, and wait for a session acceptance message from the second subscriber; responsive to receiving the session acceptance message from the second subscriber, the control system is further adapted to transmit the session acceptance message to the first subscriber through the session control interface, transmit an update credit control request message through the charging interface to the OCS to obtain a quota for the first subscriber for the session, and wait for an update credit control answer message from the OCS.