Charging Event

Description

A charging event is a fundamental unit of charging information in 3GPP networks. It is defined as a set of charging information forwarded by the Charging Trigger Function (CTF) towards the Charging Data Function (CDF) for offline charging, or towards the Online Charging System (OCS) for online charging. Each charging event corresponds to exactly one chargeable event, which is an activity that may incur a charge, such as a voice call, a data session, or the use of a specific service.

The charging event serves as the atomic unit of charging data. It contains all the necessary information for the charging system to rate and bill the usage, including identifiers, timestamps, volume counts, and service-specific parameters. The CTF, which is typically located in the network element that provides the service (e.g., SGSN, GGSN, P-GW, IMS node), detects chargeable events and generates charging events accordingly.

In offline charging, charging events are sent to the CDF, which processes them and generates Charging Data Records (CDRs). These CDRs are then transferred to the billing domain via the Charging Gateway Function (CGF). In online charging, charging events are sent to the OCS, which performs real-time rating and credit control. The OCS may authorize the service, deny it, or grant a quota based on the subscriber's account balance.

The charging event concept is specified in multiple 3GPP specifications, including TS 32.240 (Charging architecture and principles), TS 32.251 (Packet Switched domain charging), TS 32.270 (IMS charging), and others. It has been part of the 3GPP charging framework since Release 8 and its definition has remained unchanged through Release 19, demonstrating its stability and fundamental importance.

Purpose & Motivation

The charging event exists to provide a standardized and granular way to capture and convey charging information in 3GPP networks. Before the introduction of this concept, charging systems often relied on proprietary or technology-specific mechanisms, which made it difficult to support multiple access technologies, roaming, and converged services. The charging event abstraction allows the charging system to be independent of the underlying network technology and service type.

The charging event solves the problem of how to represent a chargeable occurrence in a consistent manner across different network domains. By defining a charging event as a set of charging information that matches exactly one chargeable event, 3GPP ensures that the charging system can accurately correlate usage with billing. This is essential for both offline and online charging, as it enables precise rating and prevents over- or under-charging.

Furthermore, the charging event concept facilitates the integration of new services and charging models. As new services are introduced, they can define their own charging events with specific parameters, while still adhering to the common framework. This extensibility has allowed the 3GPP charging architecture to evolve and support a wide range of services, from basic voice and data to advanced IMS and IoT applications.