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Realizing real-time charging

Ericsson Review, no. 03, 2006

Written by: Jaco Fourie

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Real-time charging differs from non-real-time charging. Among other things, it is an integral, ongoing part of the service, not an after-service activity; it does not handle the aggregation of information; in converged networks, the subscriber identity is not necessarily the MSISDN; and it must accommodate different classes of service and content. With these differences in mind, Ericsson has defined a real-time charging mechanism and process for assessing charges for specific services.

 

The author describes the real-time charging network along with its main components (serving elements, charging control, and business support systems). He also briefly describes operator scenarios, a logical evolution of real-time charging, benefits, and standardization.

Background

In the early 1990s, operators in the UK attempted to offer a credit-limiting service (stopping users from spending more than a predefined limit) that processed call detail records (CDR) as they arrived from the network and blocked service when customers reached their credit limit. The service was unsuccessful, however, because processing was delayed (sometimes up to several days) and thereby failed to fulfill user expectations and service providers’ objectives.

In 1996, prepaid services emerged as a value-added service (VAS). At that time, many people in the industry saw these as yet another “phase” but in reality prepaid services helped revolutionize the way in which the industry does business. Prepaid services have accelerated growth in the industry and currently account for the main source of new subscribers (75% of net subscriber additions). Analysts predict that prepaid subscriptions will represent 65% of the global mobile subscriber base by 2010. At present, this figure is 59%. The success of prepaid services can largely be attributed to two main factors:

  • people need not bind themselves to a 12- or 24-month contract to have access to mobile communications services; and
  • users on a limited budget have greater control over their spending (this is the main reason people choose prepaid subscriptions).

Today, prepaid subscriptions are no longer considered a value-added service. Instead they are one of two payment options enabled by an underlying real-time charging environment. This environment, however, has presented the industry with a number of challenges, in particular because no standards had been defined for it. As a result, many different approaches were tried, including SIM-based applications, call-trunking nodes, and intelligent network (IN) implementations. The problem is not only one of standards, however. There is also the issue of how charging is to be handled in real time (real-time charging broke all established rules governing charging and billing before the introduction of prepaid services).

Before the advent of prepaid services, only non-real-time mechanisms had been defined for charging in existing standards. An interim approach was needed. In 2000, the intelligent network approach was adopted as the de facto standard for managing real-time, prepaid voice services. This solution fell short for non-voice services, however, and one additional approach emerged: service-charging nodes. The use of service-charging nodes to handle charging on behalf of service nodes in the network introduces other complications, however.

 

The nature of real-time charging

Real-time charging differs from non-real-time charging:

  • It is an integral, ongoing part of the service, not an after-service activity. As such it must be aware of and facilitate all relevant interactions to permit charging and supervision.
  • It cannot handle the aggregation of information; that is, one cannot first gather information from multiple network elements and then calculate a cumulative charge.
  • In converged networks, the subscriber identity is not necessarily the same as the mobile station international subscriber directory number (MSISDN). Therefore, when a service is to be used, multiple identities must be resolved against one account.
  • It was not standardized until 2005 when the 3GPP IMS standard was defined.
  • It must accommodate different classes of service ranging from the bearer to service (for example, SMS and MMS) and content. Operators must identify the value of each service. If, for example, operators charge for GPRS data volume, an MMS message, and a just-purchased background image, the subscriber will perceive the service as bad value for money and not use it.