Section: 4.1 Charging mechanisms 4.1.0 General
Content: 3GPP networks provide functions that implement offline and/or online charging mechanisms on the domain (e.g. EPC), subsystem (e.g. IMS) and service (e.g. MMS) levels. In order to support these charging mechanisms, the network performs real-time monitoring of resource usage on the above three levels in order to detect the relevant chargeable events. The charging levels are further described in clause 5.3. In offline charging, the resource usage is reported from the network to the BD after the resource usage has occurred. In online charging, a subscriber account, located in an OCS or CCS, is queried prior to granting permission to use the requested network resource(s). Typical examples of network resource usage are a voice call of certain duration, the transport of a certain volume of data, or the submission of a MM of a certain size. The network resource usage requests may be initiated by the UE (MO case) or by the network (MT case). Offline and online charging may be performed simultaneously and independently for the same chargeable event. Clause 5.5 provides further insight into potential utilisation of the charging information produced by the offline and online charging mechanisms.