Description
QoS flow Based Charging (QBC) is a charging architecture defined within the 3GPP 5G Core network, specified primarily in the 32-series (Charging) specifications. It represents a paradigm shift from bearer-based charging in 4G EPS to a more granular, flow-based model aligned with the 5G Core's service-based architecture and QoS model. In 5G, user plane traffic is organized into QoS Flows, each with a unique QoS Flow Identifier (QFI) and a specific QoS profile defining parameters like 5G QoS Identifier (5QI), Guaranteed Flow Bit Rate (GFBR), and Maximum Flow Bit Rate (MFBR). QBC operates by generating Charging Data Records (CDRs) or Charging Events that are correlated to these individual QoS Flows.
The architecture involves several key network functions. The Session Management Function (SMF) is central, as it establishes, modifies, and releases QoS Flows within a PDU Session. The SMF interacts with the Policy Control Function (PCF) to receive policy and charging control (PCC) rules. These PCC rules include charging instructions that dictate how a specific service data flow, mapped to a QoS Flow, should be charged. When charging is triggered, the SMF, acting as a Charging Trigger Function (CTF), collects relevant charging information such as QoS Flow identifiers, data volumes, duration, and associated network slice information. It then forwards this information to the Charging Data Function (CDF) or Online Charging System (OCS) via the Nchf service-based interface.
How QBC works is intrinsically linked to the 5G QoS model. A single PDU Session can contain multiple QoS Flows—for example, one for high-priority voice traffic, one for best-effort internet browsing, and another for a low-latency gaming service. QBC allows the operator to apply distinct charging rates, quotas, or billing models to each of these flows independently. The charging data records can capture not just volume and time, but also the specific 5QI value, the network slice instance (S-NSSAI) serving the flow, and the data network name (DNN). This enables highly detailed billing reports and facilitates service-differentiated pricing, such as charging a premium for guaranteed low-latency flows or offering zero-rating for specific application flows.
Purpose & Motivation
QBC was created to address the limitations of the EPS bearer-based charging model, which was not granular enough for the diverse service landscape envisioned for 5G. In 4G, charging was typically associated with an EPS bearer, which aggregated traffic with similar QoS requirements. This made it difficult to implement fine-grained, service-specific charging policies, especially as networks evolved to support network slicing and a wide variety of vertical industry services with distinct QoS profiles.
The primary problem QBC solves is enabling monetization models that match the technical capabilities of 5G. With network slicing, IoT services, ultra-reliable low-latency communication (URLLC), and enhanced mobile broadband (eMBB) all coexisting on the same infrastructure, a one-size-fits-all charging approach is inadequate. QBC provides the mechanism to charge based on the actual value or cost of delivering a specific QoS level. This allows operators to create innovative tariff plans, offer service level agreement (SLA)-based billing to enterprise customers, and implement fair usage policies that consider the quality of service consumed, not just the raw data volume. Its introduction was motivated by the business need to monetize 5G's advanced capabilities beyond simple data buckets.
Classification
Release Timeline
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (14 CRs across 4 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-15, normative work from Rel-16.
In Release 16, the QBC (QoS flow Based Charging) function was newly enhanced to support offline only charging for QoS flow based charging. It specifically introduced a synchronized "Roaming Charging Profile" for use in roaming scenarios, which defines a common set of chargeable events, categories, and trigger thresholds for QoS Flows between the VPLMN and HPLMN. This allows the SMF to generate charging data for interconnect charges, with procedures detailed for both the V-SMF and H-SMF interacting with their respective CHF.
- Add offline only charging for QoS flow based charging TS 32.255CR0041
In Release 17, the enhancements for QoS flow Based Charging (QBC) primarily involved corrections and clarifications to existing procedures. These included correcting the triggers and conditions used by the SMF for generating charging data, such as the UPF trigger and the set of default chargeable events. The updates also refined the handling of the Roaming Charging Profile and its reporting mechanisms, particularly for roaming scenarios between VPLMN and HPLMN.
In Release 18, specific enhancements were made to the QoS flow Based Charging (QBC) function, including the introduction of a defined procedure for QBC Charging Session Continuity Identification at V-SMF change. The release also provided corrections and clarifications on the usage of QBC triggers and its relationship with Flow Based Charging (FBC) within 5G data connectivity charging.
- Clarification on QBC triggers TS 32.255CR0445
- Rel-18 CR 32.255 Correction on FBC and QBC in 5G data connectivity charging TS 32.255CR0531
- Rel-18 CR 32.255 Correction on the QBC Trigger Description TS 32.255CR0547
- Rel-18 CR 32.255 Correction of usage of FBC and QBC TS 32.255CR0550
- Rel-18 CR 32.255 QBC Charging Session Continuity Identification at V-SMF Change TS 32.255CR0466
- Correction of UPFId in QBC TS 32.298CR0928
+ 1 more changes
In Release 20, the enhancements for QoS flow Based Charging (QBC) primarily involved corrections and clarifications to its existing descriptions and procedures. The release further detailed the application of the "Roaming Charging Profile" for synchronizing chargeable events and trigger thresholds between PLMNs in roaming scenarios, including specific procedures for scenarios like PDU session handover from EPS to 5GS and disaster roaming. It also clarified the generation of Charging Data Requests and the conditions for opening and updating Roaming QBC CHF CDRs.
- Rel-20 CR 32.255 Correct some descriptions on QoS flow Based Charging TS 32.255CR0619
Explore further
Broader topics and technologies where QBC plays a role.
Defining Specifications
3GPP specifications that define or reference QBC, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 32.255 vk10 | Telecom Management; Charging for 5G Data Connectivity | Rel-20 |
| TS 32.291 vj40 | Charging Management: Service-Based Interface Protocol | Rel-19 |
| TS 32.298 vj30 | Charging Data Record (CDR) Parameter Specification | Rel-19 |
