Offline Charging System Features
  • IMS Offline charging Interface i.e. Rf Interface (3GPP TS 32.240, 3GPP TS 32.296, 3GPP 32.299)
  • Accounting Request (ACR) and Accounting Answer(ACA) [ RFC 3588]
  • Support for Start, Interim and Stop Charging Events/Records
  • CDR logging into Database and ASN1 BER encoded files
  • Correlation Function for correlation of multiple Charging Records
  • Charging Gateway Function for communication with external Billing System
Offline CS Architecture

The Offline Charging Server (Offline CS) is written using the AMPS framework, which is an Asynchronous Event Based framework that provides two major facilities to us as application writers:

  • Hides the implementation details of Operating System specific API, thus making any code written on top of AMPS to be portable across various operating systems.
  • Provides extensive support for asynchronous and event driven programming paradigm specifically tailored for writing protocol servers for networking and telecommunication domains.

Both of the facilities above make AMPS a prime candidate to be used in the development of Offline Charging Server, hence the choice to use AMPS in the Offline CS design and development.

AMPS framework is implemented as a shared library, and lies at the bottom of the architecture . The diameter base protocol stack has been implemented as a shared library, and lies on top of AMPS.  The communication between Diameter Base Protocol stack and AMPS is through direct function calls and through callback functions. 

Offline CS itself is implemented as an AMPS module. The Rf interface which is part of Offline CS functionality, is implemented as a standalone AMPS module. For functionality requiring access to DBMS, a standalone AMPS module is implemented, known as Database Module. Any access to DBMS required by any constituent component of Offline CS will be serviced through the Database module and never through direct DBMS interaction. Please refer to figure 1 for a visual display of the broad term Offline CS Architecture.

Offline CS Architecture