Account balance

Description

In 3GPP charging and policy management, the term "Account balance" refers to a numerical value that represents the current state of a subscriber's account, from which decisions about service delivery can be made. This concept is defined in 3GPP TS 32.296 and TS 32.825, which specify the charging and policy control frameworks. The account balance is typically managed by the Online Charging System (OCS) or the Policy and Charging Rules Function (PCRF) in 4G, or the Policy Control Function (PCF) and Charging Function (CHF) in 5G. It is used to determine whether a subscriber is allowed to access a service, and if so, under what conditions (e.g., QoS, duration, volume).

The account balance can represent various types of resources, such as monetary units, data volume, time, or service-specific credits. It is a dynamic value that is updated in real-time as the subscriber uses services. For example, in a prepaid scenario, the account balance decreases as the subscriber consumes data or minutes. When the balance reaches a certain threshold, the network may take actions such as notifying the subscriber, reducing the QoS, or terminating the service. The balance can also be replenished through top-ups or recharges.

The architecture for managing account balances involves several network elements. The OCS (Online Charging System) is responsible for real-time charging and balance management. It interacts with the SMF (Session Management Function) or PGW (Packet Data Network Gateway) to authorize and monitor service usage. The PCF provides policy rules that may be based on the account balance, such as spending limits or fair usage policies. The CHF (Charging Function) in 5G converges charging and provides balance information to other functions. The account balance is often stored in a subscriber database, such as the Unified Data Repository (UDR) or a dedicated charging database.

The procedure for using the account balance typically involves the following steps: When a subscriber requests a service, the network checks the account balance to determine if sufficient credit is available. If so, the service is authorized, and the balance is reserved or deducted. During the service, the network monitors usage and updates the balance accordingly. If the balance is exhausted, the service may be terminated or downgraded. The account balance can also be used for postpaid subscribers, where it represents the accumulated charges that will be billed at the end of the billing cycle.

The definition of account balance has evolved over time. In Release 8, it was defined as "the current value of an account of service usage." In Release 9, the definition was changed to "represents the current numerical value from which service delivery decisions can be determined." This change broadened the concept to emphasize its role in decision-making, not just tracking usage. The definition has remained stable since then, with only minor formatting changes. This reflects the maturity of the charging framework and the stability of the concept.

In summary, the account balance is a fundamental concept in 3GPP charging and policy management. It provides a real-time view of a subscriber's available resources and enables dynamic service control. Its accurate management is essential for operators to prevent revenue leakage, enforce fair usage, and provide personalized services.

Purpose & Motivation

The concept of account balance exists to enable real-time control of service delivery based on a subscriber's available resources. In traditional postpaid systems, billing was done at the end of the month, and there was no real-time enforcement of spending limits. This led to issues such as bill shock and fraud. The account balance, managed by online charging systems, allows operators to authorize and monitor service usage in real-time, ensuring that subscribers do not exceed their credit limits. It solves the problem of revenue assurance and provides a mechanism for prepaid and hybrid charging models.

The motivation for a standardized definition of account balance comes from the need for interoperability between different charging systems and network elements. In a multi-vendor environment, it is essential that all components have a common understanding of what the account balance represents and how it should be used. The 3GPP specifications define the semantics and the protocols for exchanging balance information, such as the Diameter Credit-Control Application (DCCA) and the 5G charging service-based interfaces. This allows operators to deploy flexible charging models, such as tiered pricing, time-based charging, and volume-based charging.

Furthermore, the account balance is a key input for policy decisions. For example, a subscriber with a low balance might be subject to a different QoS or be blocked from accessing certain services. The integration of charging and policy control, known as Policy and Charging Control (PCC), allows operators to create sophisticated service offerings. The account balance also enables new business models, such as sponsored data, where a third party pays for the subscriber's usage. By standardizing the concept, 3GPP ensures that these models can be implemented across different networks and vendors.