Tariff Determination Instance

Description

The Tariff Determination Instance is a fundamental concept in 3GPP charging management, specifically defined in the charging specifications TS 29.458 and TS 29.658. It represents a particular charging-related process that involves a corresponding communication between a charge determination point and a charge registration/charge generation point. This instance is responsible for determining the applicable tariff for a communication event based on various parameters such as time of day, subscriber profile, service type, and network conditions. The charge determination point is typically a functional entity within the charging system, such as the Charging Trigger Function (CTF) or the Charging Data Function (CDF), while the charge registration/charge generation point is responsible for recording or generating the charging information. The communication between these points ensures that the correct tariff is applied and that the charging data is accurately recorded for billing purposes.

In the context of the 3GPP charging architecture, the Tariff Determination Instance operates within the Online Charging System (OCS) or the Offline Charging System (OFCS). For online charging, the instance interacts with the Online Charging Function (OCF) to authorize and rate the service usage in real-time. For offline charging, it works with the Charging Gateway Function (CGF) to collect and process Charging Data Records (CDRs). The tariff determination process involves evaluating the tariff period, tariff sequence, and other tariff-related parameters to compute the charge for a specific communication event. This ensures that the billing is accurate and reflects the applicable pricing model, which may include time-based, volume-based, or event-based tariffs.

The Tariff Determination Instance is crucial for enabling flexible and dynamic charging in mobile networks. It allows operators to define complex tariff structures that can vary based on time, location, subscriber category, and service type. For example, a network may apply different tariffs during peak and off-peak hours, or offer special rates for certain subscribers. The instance ensures that these rules are consistently applied across all charging events. It also supports the generation of detailed charging records that can be used for billing, revenue assurance, and analytics. The communication between the charge determination point and the charge registration/generation point is typically based on standardized protocols such as Diameter or the 5G Service Based Architecture (SBA) interfaces, ensuring interoperability between different vendors' equipment.

From an implementation perspective, the Tariff Determination Instance is realized through a combination of charging rules, tariff tables, and charging functions. The charging rules define the conditions under which a particular tariff applies, while the tariff tables contain the actual rates and parameters. The charging functions execute the rules and generate the charging data. The instance is identified by a unique identifier and is associated with a specific communication event or session. It may be invoked multiple times during a session if the tariff changes due to a tariff period switch-over or other triggers. The instance also handles the interaction with the subscriber's account balance for online charging, ensuring that the service is only provided if sufficient credit is available.

In summary, the Tariff Determination Instance is a key enabler for accurate and flexible charging in 3GPP networks. It provides a standardized mechanism for determining and applying tariffs, ensuring that operators can implement diverse pricing strategies while maintaining interoperability and consistency. Its role is essential for both online and offline charging scenarios, and it is a critical component of the overall charging management framework.

Purpose & Motivation

The Tariff Determination Instance exists to provide a standardized and flexible mechanism for determining the applicable tariff for a communication event in mobile networks. Before its introduction, charging systems often relied on proprietary or vendor-specific methods for tariff determination, leading to interoperability issues and limited flexibility. The 3GPP defined this concept to enable operators to implement complex tariff structures that can vary based on time, subscriber profile, service type, and other parameters, while ensuring that the charging process is consistent and accurate across different network elements and vendors.

The primary problem it solves is the need to dynamically determine the correct tariff for each communication event in real-time or near-real-time. This is particularly important for online charging, where the service must be authorized based on the subscriber's available credit and the applicable tariff. The Tariff Determination Instance provides a clear separation between the charge determination point (which decides the tariff) and the charge registration/generation point (which records the charging information), allowing for modular and scalable charging architectures. It also supports the generation of detailed charging records that can be used for billing, revenue sharing, and business intelligence.

Historically, as mobile networks evolved from voice-centric to data-centric services, the complexity of tariff structures increased significantly. Operators needed to offer differentiated pricing for various services, such as voice, SMS, data, and value-added services, often with time-based or volume-based variations. The Tariff Determination Instance was introduced in Release 8 to address these needs, providing a standardized framework that could accommodate diverse charging models. Its continued presence in subsequent releases, up to Release 19, demonstrates its enduring relevance and adaptability to new charging requirements, including those for 5G and IoT services.