Description
The Charging Function (CHF) is a fundamental component within the 5G Core Network (5GC) architecture, specifically part of the Charging framework. It operates as a producer of charging events, interacting with other Network Functions (NFs) like the Session Management Function (SMF) and Policy Control Function (PCF) via service-based interfaces (e.g., Nchf). The CHF is responsible for collecting usage information, applying charging policies, and generating Charging Data Records (CDRs) or Charging Events. These records are then forwarded to the Charging Data Function (CDF) for long-term storage and eventual processing by the billing system.
Architecturally, the CHF is defined as a standalone Network Function that can be deployed independently, supporting both offline and online charging modes. In online charging, it performs credit control in real-time, granting or denying service units based on a user's account balance and policy rules. This involves direct interaction with the user's balance management system. For offline charging, it collects usage data after the service is rendered, correlating events from multiple NFs to produce consolidated CDRs. The CHF supports a converged charging system, meaning it can handle charging for any service type (e.g., data, voice, IoT, network slicing) through a unified framework.
Key components of the CHF's operation include the Charging Trigger Function (CTF), which is logically embedded within other NFs like the SMF to detect chargeable events, and the Charging Data Function (CDF) for record storage. The CHF itself implements the charging logic, determining tariff times, applying rating, and managing quotas. It uses standardized reference points such as Nchf (for service-based communication with other NFs) and Rf/Ga (for legacy offline/online charging interfaces if needed). Its design is highly flexible, supporting event-based, session-based, and volume-based charging, which is essential for 5G's diverse service offerings like network slicing and edge computing.
The CHF's role is critical for monetizing 5G services. It enables operators to implement sophisticated, real-time charging strategies, such as dynamic pricing, QoS-based charging, and slice-specific billing. By decoupling charging from session management, 5G allows for more agile service deployment and innovative business models, including third-party service charging. The CHF ensures that all network resource usage is accurately measured, rated, and recorded, forming the basis for revenue assurance and customer billing in modern telecom networks.
Purpose & Motivation
The CHF was introduced in 3GPP Release 15 as part of the new 5G Core (5GC) architecture to address the limitations of previous charging systems in 4G EPC. In 4G, charging was tightly coupled with specific network elements like the PGW (via Gy/Gz interfaces), which made it inflexible and difficult to adapt to new services. The 4G charging architecture was primarily designed for traditional mobile broadband, struggling with real-time, service-differentiated charging required for IoT, network slicing, and edge services.
The primary motivation for creating a dedicated CHF was to enable a converged, service-based charging framework that could support the diverse use cases promised by 5G. This separation allows charging logic to be applied independently of the underlying network topology or session state, facilitating innovation. It solves the problem of monolithic charging systems by providing a modular, cloud-native NF that can scale dynamically and integrate with modern IT systems via APIs.
Historically, charging evolved from simple call detail records in circuit-switched networks to more complex data charging in packet-switched networks. The CHF represents the next step, designed for a software-defined, service-oriented core. It addresses the need for real-time charging for on-demand services, support for network slicing where each slice may have a different charging model, and the ability to charge for third-party applications and services directly through the network. This enables new revenue streams and business models essential for 5G's economic viability.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (519 CRs across 6 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the CHF (Charging Function) was newly introduced as a central charging entity for the 5G System, replacing the OCS and defined with service-based interfaces like Nchf. It supports converged offline and online charging, interacting with the SMF via reference points N40, N41, and N42 for PDU session and mobility-related charging, and enables spending limit control. The release also formalized CHF discovery and selection, integrating it into the overall 5G architecture for policy and charging control.
- 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 in charging mechanisms TS 32.240CR0399
- Introduce the 5G charging in clause 3 TS 32.240CR0401
- Charging mode clarifications in Converged Charging System TS 32.240CR0402
+ 38 more changes
In Release 16, the CHF was enhanced with a new, comprehensive offline-only charging capability, including procedures, triggers, and Charging Data Record (CDR) generation for entities like the SMF and for QoS flow-based charging. This release also introduced specific CHF identifiers, such as the CHF Group ID and instance ID, into the charging information and formally defined the N41 and N42 reference points for the AMF's interaction with the CHF within the charging architecture. Furthermore, it added support for new notification types and identifiers, like the Access Network Charging Correlation Information and the AF charging identifier, while providing detailed charging information definitions for interworking scenarios with the EPC.
- CHF Group ID TS 29.510CR0284
- CHF set and instance Id in charging information TS 29.512CR0431
- Support of “Access Network Charging Correlation Information” notification TS 29.514CR0109
- Support of the AF charging identifier TS 29.514CR0111
- Introduction of AMF in charging architecture TS 32.240CR0409
- Add offline only charging TS 32.255CR0035
+ 80 more changes
In Release 17, the CHF (Charging Function) was enhanced to support new service scenarios including 5G LAN service charging, Edge Computing, and URLLC, which introduced specific charging principles, quota management, and usage reporting procedures. The architecture was also extended to support Local Breakout scenarios and the reporting of the CHF's FQDN to DN-AAA servers. Furthermore, clarifications and additions were made for charging correlation identifiers and the support of PDU Sessions designated for offline charging only.
- Addition of the PDU Session with offline charging only indication TS 29.512CR0639
- Clarification of the charging correlation id TS 29.512CR0810
- Reporting FQDN of CHF to RADIUS DN-AAA server TS 29.561CR0079
- Reporting FQDN of CHF to Diameter DN-AAA server TS 29.561CR0080
- Adding Charging Id to support roaming scenario TS 29.561CR0131
- Add PGW in logical ubiquitous charging architecture- service based interface TS 32.240CR0413
+ 118 more changes
In Release 18, the CHF saw several key enhancements including its formal integration into new architectural roles, such as being added as a consumer in the LBO architecture and for spending limits in AM and UE policies. The release also introduced new charging support for specific services like TSN (Time-Sensitive Networking), 5G Satellite access, and 5MBS (5G Multicast Broadcast Services), and expanded architectural reference points, including one between an MMS node and the CHF. Furthermore, it refined B2B charging principles and added capabilities for slice-aware charging with roaming partners.
- Reference point numbers for charging TS 23.501CR3752
- 23.503 - CHF selection in Spending Limits for AM and UE Policies in the 5GC TS 23.503CR1052
- Support of CHF address(es) information TS 29.525CR0317
- Adding New Consumer for MMS in Charging Architecture TS 32.240CR0446
- Slice-aware charging for Roaming partners TS 32.240CR0467
- Add reference point between MMS node and CHF TS 32.240CR0469
+ 124 more changes
In Release 19, the CHF was enhanced to support Multi-Operator Core Network (MOCN) scenarios with new charging architecture and information requirements. The release also extended charging support for roaming, including specific interactions between the H-PCF and H-CHF, and introduced charging principles for new services like AIoT and UAS. Furthermore, it added support for CHF selection considerations in roaming scenarios and the provisioning of charging information to the AMF.
- Rel-19 CR 28.201 Add charging architecture for MOCN TS 28.201CR0017
- Rel-19 CR 28.201 Add charging requirement for MOCN TS 28.201CR0018
- Rel-19 CR 28.201 Addition of charging information for MOCN TS 28.201CR0023
- CHF selection aspects TS 29.507CR0316
- Extending Charging support in 5GC TS 29.507CR0335
- Extending Charging support in 5GC TS 29.512CR1337
+ 125 more changes
In Release 20, the CHF was enhanced with new information elements to support charging for multi-modality services and to address the charging impacts from enhanced QoS handling in XRM. The release also included corrections and clarifications for QoS flow-based charging procedures and for PDU Session ID handling specific to V-SMF charging in EPS-5GS interworking scenarios.
- Add informatin elements to support charging aspects of multi-modality service TS 32.255CR0606
- Rel-20 TS 32.255 Add information elements to address charging impacts from enhanced QoS handling in XRM TS 32.255CR0616
- Rel-20 CR 32.255 Correct some descriptions on QoS flow Based Charging TS 32.255CR0619
- Rel-20 CR 32.255 Correction on PDU Session ID Handling for V-SMF Charging in EPS–5GS Interworking TS 32.255CR0622
Explore further
Broader topics and technologies where CHF plays a role.
Defining Specifications
3GPP specifications that define or reference CHF, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 23.501 vk00 | 5G System Architecture Stage 2 | Rel-20 |
| TS 23.503 vk00 | 5G Policy and Charging Control Framework | Rel-20 |
| TS 28.201 vj20 | 5G Network Slice Performance Analytics Charging | Rel-19 |
| TS 28.203 vi10 | Charging management | Rel-18 |
| TS 28.204 vi11 | Charging management | Rel-18 |
| TR 28.815 vh00 | Charging Study for Edge Computing | Rel-17 |
| TR 28.816 vh00 | Charging for 5G Cellular IoT | Rel-17 |
| TR 28.822 vh00 | Charging for 5G LAN Services Study | Rel-17 |
| TR 28.827 vi00 | Technical Report on 5G Charging for Roaming Scenarios | Rel-18 |
| TR 28.840 vi10 | Technical Report | Rel-18 |
| TS 28.849 vj10 | CAPIF Phase2 Charging Study | Rel-19 |
| TS 29.507 vj40 | 5G Access & Mobility Policy Control Service | Rel-19 |
| TS 29.510 vj50 | NRF Service Based Interface Protocol | Rel-19 |
| TS 29.512 vj40 | 5G Session Management Policy Control Service | Rel-19 |
| TS 29.513 vj40 | 5G PCC Signalling Flows & QoS Mapping | Rel-19 |
| TS 29.514 vj40 | 5G System; Policy Authorization Service; Stage 3 | Rel-19 |
| TS 29.525 vj40 | 5G UE Policy Control Service Stage 3 | Rel-19 |
| TS 29.561 vj30 | 5G Interworking with External Data Networks | Rel-19 |
| TS 29.594 vj20 | 5G Spending Limit Control Service Stage 3 | Rel-19 |
| TS 32.240 vj40 | Charging Management Architecture & Principles | Rel-19 |
| TS 32.255 vk10 | Telecom Management; Charging for 5G Data Connectivity | Rel-20 |
| TS 32.256 vj40 | 5G Connection & Mobility Charging Spec | Rel-19 |
| TS 32.257 vj00 | Edge Computing Charging Management | Rel-19 |
| TS 32.260 vj10 | IMS Charging Management | Rel-19 |
| TS 32.271 vj20 | 3GPP LCS Charging Management Spec | Rel-19 |
| TS 32.277 vj20 | Charging Management for Proximity Services (ProSe) | Rel-19 |
| TS 32.279 vj00 | 5G MBS Session Converged Charging | Rel-19 |
| TS 32.290 vj50 | 5G Charging for Service Based Interface | Rel-19 |
| TS 32.291 vj40 | Charging Management: Service-Based Interface Protocol | Rel-19 |
| TR 32.846 vh00 | Charging for ProSe in 5GS | Rel-17 |
| TR 32.847 vi00 | Technical Report | Rel-18 |
| TS 33.127 vj50 | Lawful Interception Architecture and Functions | Rel-19 |
| TS 33.128 vj50 | 3GPP TS 33.128: Lawful Interception Protocols | Rel-19 |
| TS 33.515 vk00 | 5G SMF Security Assurance Specification | Rel-20 |
| TR 33.928 vj10 | ADMF Logic for LI Provisioning | Rel-19 |