Event Based Charging Function

Description

The Event Based Charging Function (EBCF) is a fundamental component within the 3GPP Online Charging System (OCS). Its role is to execute charging logic in real-time for service events. Unlike session-based or volume-based charging, which are continuous, event-based charging is triggered by discrete occurrences. The EBCF receives charging events from network functions like the Gateway GPRS Support Node (GGSN), Packet Data Network Gateway (PGW), or IMS Call Session Control Functions (CSCFs) via the Ro or Gy reference points. These events carry information such as the subscriber identity, event type, and relevant service parameters.

Architecturally, the EBCF resides within the OCS and works in conjunction with the Account Balance Management Function (ABMF) and the Rating Function (RF). When a charging request arrives, the EBCF processes it. It first performs subscriber identification and retrieves the relevant account information and charging rules from the ABMF. It then uses the RF to determine the monetary or non-monetary cost (in units like credits) associated with the specific event. This rating can be complex, depending on factors like event type, service type, location, time of day, and subscriber tier. After rating, the EBCF instructs the ABMF to deduct the appropriate amount from the subscriber's balance in real-time.

How it works is centered on policy and real-time authorization. For each event, the EBCF must make an immediate decision: authorize the event (if sufficient balance exists) or deny it. For example, when a user sends an MMS, the MMS server sends a charging event to the OCS. The EBCF rates this 'MMS submission' event, checks the balance, and if authorized, allows the MMS to be sent while deducting the cost. It then returns a response to the network element. The EBCF supports various event types, including service events (e.g., content download, SMS, MMS), service configuration events (e.g., activating a call forwarding rule), and management events (e.g., balance top-up). It generates Charging Data Records (CDRs) for billing and auditing purposes.

Purpose & Motivation

The EBCF was created to address the limitations of traditional, simplistic charging models based solely on call duration or megabyte counts. As mobile networks evolved to offer a vast array of services beyond voice—such as messaging (SMS/MMS), content downloads, location-based services, and IMS features—operators needed a flexible way to charge for these discrete, non-continuous transactions. A flat data rate or per-minute voice charge could not capture the value or cost structure of sending an MMS or accessing a premium game level. The EBCF provides the mechanism for this granular, service-aware charging.

Introduced in Release 8 as part of the enhanced OCS architecture, the EBCF solved the problem of real-time credit control for event-based services. It enabled prepaid offerings for non-session services, which was a major business requirement. Without it, operators would have to rely on less accurate offline charging or forced all services into session-based models. The EBCF allows operators to define sophisticated tariff plans that charge different amounts for different types of events, fostering service innovation and personalized pricing. It is a key enabler for the monetization of the vast service ecosystem in modern mobile networks.