OCF, OCS, and OFCS in LTE: Understanding the Differences

This page explains the differences between OCF, OCS, and OFCS in LTE (Long-Term Evolution) networks. We’ll explore the functions of each and how they relate to online and offline charging mechanisms.

In LTE, two primary charging methods exist: online and offline charging. Offline charging utilizes the Rf interface, while online charging uses the Ro interface.

The Charging Trigger Function (CTF) is a critical component embedded within network elements like the P-GW (Packet Data Network Gateway), S-GW (Serving Gateway), and SGSN (Serving GPRS Support Node). The CTF’s role is to initiate “charging events.”

Figure 1: OCS and OFCS architecture illustrating information flows.

LTE OCS - Online Charging System | OCF - Online Charging Function

Figure 2: Online Charging Architecture

• OCS (Online Charging System):

  • In an OCS setup, “Charging events” are received by the Online Charging Function (OCF).

  • The OCF then makes decisions about resource usage based on the Rating Function (RF) and the Account Balance Management Function (ABMF). Essentially, it determines how much the user should be charged in real-time.

  • In Figure 2, CTF represents the Charging Trigger Function, OCF stands for Online Charging Function, ABMF represents Account Balance Management Function, and RF represents the Rating Function.

LTE OFCS - Offline Charging System

Figure 3: Offline Charging Architecture

• OFCS (Offline Charging System):

  • In an OFCS, charging events are received by the Charging Data Function (CDF).

  • The CDF generates CDRs (Charging Data Records). These records detail the user’s service consumption. The CDF then transmits these CDRs to the Charging Gateway Function (CGF).

  • The CGF acts as a gateway between the 3GPP LTE network and the billing systems. It essentially translates the network’s charging information into a format the billing system can understand.

  • The CGF then transmits these CDRs to the billing domain for processing.

  • In Figure 3, CTF represents the Charging Trigger Function, CDF stands for Charging Data Function, CGF stands for Charging Gateway Function, and BD stands for Billing Domain.

In Summary:

• OCF: The core function within the online charging system responsible for making real-time charging decisions.
• OCS: The system that handles real-time, online charging based on immediate account balance checks and rating rules.
• OFCS: The system that handles offline charging by collecting usage data and generating charging records for later billing.

Reference: 3GPP TS 32.240 version 6.2.0 Release 6

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