A charging server is an application that calculates billing charges for a wireless subscriber. The CMP system supports both online and offline charging servers:
- An online charging server (OCS) calculates charges against a prepaid account for an event and returns information on how long the subscriber can use the service; it can affect, in real time, the service rendered.
- An offline charging server (OFCS) calculates charges for a service to an account, and does not affect (in real time) the service rendered.