Description
The Session Based Charging Function (SBCF) is a fundamental logical function within the 3GPP Online Charging System (OCS) architecture, as defined in the Telecommunication Management (TS 32.2xx) series. It operates as the central engine for real-time, session-based credit control. The SBCF interacts with network elements known as Charging Trigger Functions (CTFs)—such as the P-GW, S-CSCF, or MME—via the standardized Ro reference point using the Diameter Credit Control Application (DCCA) protocol. When a subscriber initiates a service session (e.g., a voice call, a data session, an IMS session), the CTF sends a credit control request to the SBCF. The SBCF then performs rating based on the subscriber's profile, service details, and tariff plans, and reserves an appropriate amount of credit from the subscriber's account.
Upon successful credit reservation, the SBCF grants a quota (e.g., data volume, time duration) to the network element, authorizing the service to proceed. The network element then monitors the resource usage against this quota. As the quota is consumed, the CTF may send intermediate update requests to the SBCF to report usage and request additional credit. The SBCF manages these updates, potentially applying re-rating, and grants new quotas. This process continues until the session ends or the subscriber's credit is exhausted. If credit runs out, the SBCF instructs the network element to terminate or redirect the service session. Throughout this cycle, the SBCF generates charging events that are forwarded to the Charging Gateway Function (CGF) or directly to the billing domain for final bill calculation.
Architecturally, the SBCF is often implemented as part of a larger OCS node alongside other functions like the Account Balance Management Function (ABMF) and the Rating Function (RF). It plays a critical role in enabling prepaid services, spending limit controls, and real-time policy enforcement. By managing sessions dynamically, it allows operators to offer complex tariff plans, such as tiered data bundles, time-of-day rates, and service-specific charging, while guaranteeing that no revenue is lost due to unpaid usage. Its operation is crucial for the convergence of charging across access technologies (2G/3G/4G/5G) and service domains (voice, data, messaging, IMS).
Purpose & Motivation
The SBCF was created to solve the limitations of traditional offline (postpaid) charging, which could not prevent service usage when a subscriber had insufficient funds or credit. This was a significant business risk for operators, especially with the rise of prepaid mobile services. Early prepaid systems were often proprietary, siloed, and could not easily support new services or convergent charging across multiple service types. The standardization of the OCS and the SBCF in 3GPP Release 5 (for IMS) and its solidification in Release 8 provided a unified, real-time charging framework.
The primary motivation was to enable operators to offer innovative prepaid and hybrid payment models for all services, including emerging IP-based services like IMS and mobile data, in a scalable and interoperable way. The SBCF addresses this by providing a standardized, session-aware credit control mechanism. It allows for immediate authorization and continuous control of resource consumption, protecting operator revenue. Furthermore, it supports the convergence of charging for voice, data, and multimedia services onto a single platform, simplifying operations and enabling personalized, real-time tariff plans that enhance customer experience and loyalty.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (52 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-8, normative work from Rel-15.
In Release 15, the SBCF (Session Based Charging Function) was fundamentally integrated into the new 5G converged charging architecture, which is based on a Service Based Interface (SBI). This introduction was part of defining the overall 5G system charging principles, including the specification of the Charging Function service and its procedures within the new service-based framework as outlined in the 32.29x series of specifications.
- Introduce the Northbound API charging TS 32.240CR0394
- Introduction of 5G in charging architecture TS 32.240CR0396
- Introduction of 5G converged charging TS 32.240CR0397
- Introduction of 5G service based interface TS 32.240CR0398
- Introduction of 5G in charging mechanisms TS 32.240CR0399
- Introduce the 5G charging in clause 3 TS 32.240CR0401
+ 4 more changes
In Release 16, the Session Based Charging Function (SBCF) was enhanced to incorporate the Access and Mobility Management Function (AMF) within the charging architecture. This introduction of the AMF enables charging mechanisms for 5G connection and mobility management events. Consequently, the SBCF can now support the specific charging requirements defined for the 5G connection and mobility domain.
- Introduction of AMF in charging architecture TS 32.240CR0409
In Release 17, the SBCF (Session Based Charging Function) was enhanced to support new 5G capabilities, including the introduction of charging architectures for 5G LAN services and Edge Computing. The release also updated the logical ubiquitous charging architecture by adding and later deleting the PGW in the service-based interface representation and introduced a reference point representation for Converged Charging. Furthermore, corrections and clarifications were made for Network Slice charging and the overall charging architecture.
- Add PGW in logical ubiquitous charging architecture- service based interface TS 32.240CR0413
- Introduction of 5G DDNMF in charging architecture for 5GS TS 32.240CR0429
- Addition of the 5G LAN service charging TS 32.240CR0434
- Charging architecture for Local Breakout TS 32.240CR0439
- Addition of the architecture for 5G LAN charging TS 32.240CR0442
- Enhance charging architecture for Edge Computing TS 32.240CR0443
+ 7 more changes
In Release 18, the SBCF (Session Based Charging Function) saw its architecture extended to support new services and scenarios. Key additions included charging support for Time-Sensitive Networking (TSN) services, the integration of 5G Satellite charging, and enhanced Business-to-Business (B2B) charging principles and architecture. Furthermore, the architecture was updated to add missing consumers and reference points, such as for the Edge Enabler Server (EES), and to incorporate the MB-SMF for 5GS charging.
- Adding New Consumer for MMS in Charging Architecture TS 32.240CR0446
- Slice-aware charging for Roaming partners TS 32.240CR0467
- Add MB-SMF in charging architecture for 5GS TS 32.240CR0470
- Add charging support for TSN service TS 32.240CR0473
- Add annex for B2B charging TS 32.240CR0474
- Update B2B charging principles TS 32.240CR0475
+ 10 more changes
In Release 19, the Session Based Charging Function (SBCF) saw enhancements to support new services and clarify existing architectures. Key additions included charging support for AIoT services, CAPIF logical architecture and service charging, and new principles for UAS and disaster roaming. The release also introduced charging for MVNOs providing satellite service and provided clarifications on the converged charging refund mechanism and interactions with the Nchf.
- Introduction of GMLC in charging architecture for 5GS TS 32.240CR0491
- Rel-19 CR 32.240 Add charging support to AIoT service TS 32.240CR0510
- Rel-19 CR 32.240 CAPIF Logical Charging Architecture TS 32.240CR0511
- Rel-19 CR 32.240 CAPIF Service Charging TS 32.240CR0512
- Add charging principles for UAS TS 32.240CR0517
- Add MVNO charging which provides satellite service TS 32.240CR0518
+ 6 more changes
Explore further
Broader topics and technologies where SBCF plays a role.
Defining Specifications
3GPP specifications that define or reference SBCF, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 32.240 vj40 | Charging Management Architecture & Principles | Rel-19 |
| TS 32.272 vj00 | Charging for Push-to-Talk over Cellular (PoC) | Rel-19 |
| TS 32.278 vj00 | Monitoring Events Offline Charging Specification | Rel-19 |
| TS 32.296 vj00 | Online Charging System (OCS) Architecture | Rel-19 |
| TS 32.825 va00 | Study on Rc Reference Point for ABMF | Rel-10 |