IMS gateway systems and methods for online charging in IMS networks

A method of operating an IP Multimedia Subsystem (IMS) gateway system for providing online charging in an IMS network, wherein the IMS gateway system comprises a first interface operable to communicate with a call session control function (CSCF) according to a first protocol, a second interface operable to communicate with an online charging server (OCS) according to a second protocol, and a charging trigger system coupled to the first interface and the second interface, the method comprising:

• receiving a first message for a call session in the charging trigger system through the first interface from the CSCF wherein the first message is in the first protocol,
• processing the first message to determine whether to contact the OCS for online charging for the call session,
• generating a second message that comprises a charging request to transmit to the OCS responsive to a determination to contact the OCS,
• mapping fields of the first message in the first protocol to fields in the second message in the second protocol,
• transmitting the second message to the OCS through the second interface for online charging for the call session;
• receiving a third message from the OCS in the charging trigger system responding to the second message;
• generating a fourth message indicating whether charging was allowed or denied;
• and
• transmitting the fourth message to the CSCF through the first interface.

An IP Multimedia Subsystem (IMS) gateway system for providing online charging in an IMS network, the IMS gateway system comprising:

• an IMS service control (ISC) interface operable to communicate with a call session control function (CSCF) according to ISC protocol;
• an Ro interface operable to communicate with an online charging server (OCS) according to Ro protocol;
• and
• a charging trigger system coupled to the Ro interface and the ISC interface, the charging trigger system:
• receives a first SIP message for a call session through the ISC interface from the CSCF wherein the first SIP message is in the ISC protocol,
• processes the first SIP message and rule-based trigger points to determine whether to contact the OCS for online charging for the call session,
• generates a first Diameter Credit Control Application protocol (DCCA) message responsive to a determination to contact the OCS,
• maps fields of the first SIP message to fields in the first DCCA message,
• transmits the first DCCA message to the OCS through the Ro interface for online charging for the call session,
• receives a second DCCA message from the OCS responding to the first DCCA message,
• generates a second SIP message indicating whether charging was allowed or denied;
• and
• transmits the second SIP message to the CSCF through the ISC interface.