Description
Event Charging with Unit Reservation (ECUR) is a critical component of the 3GPP Online Charging System (OCS), defined within the Charging and Billing domain. It operates by handling charging events where service usage requires prior reservation of units (e.g., monetary credit, data volume, time) before the service is delivered. The process involves the OCS interacting with network elements like the Policy and Charging Rules Function (PCRF) or application servers to authorize and monitor resource consumption in real-time.
Architecturally, ECUR functions through a series of standardized interfaces, primarily the Sy reference point between the OCS and the PCRF, and the Ro reference point for Diameter-based communication with network elements. When a service request is initiated, the network element sends a Credit Control Request (CCR) to the OCS, specifying the required units. The OCS then performs balance checks, reserves the appropriate units from the user's account, and responds with a Credit Control Answer (CCA) granting a quota. During service delivery, usage reports are sent periodically, and the OCS deducts from the reserved units, potentially issuing new reservations as needed until the session ends or units are exhausted.
Key components include the OCS's Account Balance Management Function (ABMF) for tracking balances, the Rating Function (RF) for determining cost, and the Charging Trigger Function (CTF) in network elements that detect chargeable events. ECUR supports various service types, such as data access, voice calls, SMS, and multimedia services, allowing for flexible tariff models like prepaid and hybrid plans. Its operation ensures that charging is tightly coupled with service control, preventing revenue leakage and enabling immediate service termination upon insufficient funds. This mechanism is fundamental for real-time charging scenarios in LTE and 5G networks, where high-speed data usage demands instantaneous billing updates.
Purpose & Motivation
ECUR was developed to address the limitations of offline charging and simple event-based charging in pre-3GPP systems, which could not prevent service usage beyond a user's credit limit in real-time. As mobile services evolved to include data-intensive applications and prepaid models became widespread, there was a need for a mechanism that could reserve units upfront, ensuring that operators could control financial risk while providing seamless user experiences. ECUR enables operators to offer complex, usage-sensitive tariffs and prevent fraud by integrating charging directly with service authorization.
Its introduction in Release 8 coincided with the rollout of LTE and the enhanced OCS architecture, supporting the shift towards all-IP networks and richer service offerings. By combining event charging with reservation, it solves the problem of accurate, immediate billing for on-demand services, which is essential for customer satisfaction and operational efficiency in competitive telecom markets. Historical context includes earlier mechanisms like Advice of Charge (AoC), which were less dynamic and not integrated with policy control.
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (195 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 ECUR function was extended to support 5G converged charging for Network Slice-Specific Authentication and Authorization procedures. This introduced new charging interactions where the NSSAAF and AMF send Charging Data Requests to the CHF using the Nchf service-based interface, triggered per UE per S-NSSAI. The release also added specific charging for procedures like AAA Server triggered re-authentication and authorization revocation within this 5G architecture.
- 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
+ 30 more changes
In Release 16, the ECUR function was enhanced by formally integrating the AMF (Access and Mobility Management Function) into the charging architecture for Network Slice-Specific Authentication and Authorization procedures. Specifically, the AMF was enabled to perform converged charging for these procedures per UE and per S-NSSAI by interacting with the CHF (Charging Function) using the Nchf service-based interface. Furthermore, corrections and updates were made to the charging flows and trigger conditions for ECUR to ensure accurate operation within this new architectural framework.
- Introduction of AMF in charging architecture TS 32.240CR0409
- Introduce description of volume based charging for VoLTE in PS TS 32.251CR0514
- Update description of volume based charging in IMS TS 32.260CR0396
- IMS service based charging interface introduction TS 32.260CR0400
- CHF selection for IMS charging TS 32.260CR0401
- IMS charging general description TS 32.260CR0402
+ 5 more changes
In Release 17, the ECUR function was extended to support new 5G charging scenarios, specifically for Network Slice-Specific Authentication and Authorization procedures. This required both the NSSAAF and the AMF to interact with the Charging Function (CHF) using the Nchf service-based interface to generate charging events per UE per S-NSSAI. The enhancements introduced new chargeable events and immediate reporting for procedures like AAA Server triggered re-authentication and authorization revocation.
- 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
+ 38 more changes
In Release 18, the ECUR function was enhanced to support converged charging specifically for Network Slice-Specific Authentication and Authorization procedures. This introduced new charging interactions where both the NSSAAF and the AMF can issue Charging Data Requests to the CHF based on chargeable events per UE per S-NSSAI. The update defined specific trigger conditions and procedures for immediate reporting, integrating this functionality within the existing service-based charging architecture.
- 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
+ 32 more changes
In Release 19, the ECUR function was extended to support Network Slice-Specific Authentication and Authorization converged charging, enabling the AMF and NSSAAF to interact with the CHF using the Nchf service-based interface. This introduced new charging procedures per UE per S-NSSAI, including for AAA Server triggered re-authentication and authorization revocation, with specific trigger conditions for immediate reporting.
- 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
+ 60 more changes
Explore further
Broader topics and technologies where ECUR plays a role.
Defining Specifications
3GPP specifications that define or reference ECUR, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 28.204 vi11 | Charging management | Rel-18 |
| TS 28.849 vj10 | CAPIF Phase2 Charging Study | Rel-19 |
| TS 32.240 vj40 | Charging Management Architecture & Principles | Rel-19 |
| TS 32.251 vj00 | PS Domain Charging Management | Rel-19 |
| TS 32.254 vj21 | Charging for Northbound APIs | Rel-19 |
| TS 32.256 vj40 | 5G Connection & Mobility Charging Spec | Rel-19 |
| TS 32.260 vj10 | IMS Charging Management | Rel-19 |
| TS 32.270 vj00 | MMS Charging Management Specification | Rel-19 |
| TS 32.271 vj20 | 3GPP LCS Charging Management Spec | Rel-19 |
| TS 32.272 vj00 | Charging for Push-to-Talk over Cellular (PoC) | Rel-19 |
| TS 32.273 vj00 | MBMS Charging Management | Rel-19 |
| TS 32.274 vj10 | SMS Charging Management Specification | Rel-19 |
| TS 32.277 vj20 | Charging Management for Proximity Services (ProSe) | Rel-19 |
| TS 32.278 vj00 | Monitoring Events Offline Charging Specification | Rel-19 |
| TS 32.280 vj00 | Advice of Charge (AoC) Framework | Rel-19 |
| TS 32.291 vj40 | Charging Management: Service-Based Interface Protocol | Rel-19 |
| TS 32.296 vj00 | Online Charging System (OCS) Architecture | Rel-19 |
| TS 32.299 vj00 | Diameter Charging Applications for 3GPP | Rel-19 |
| TS 32.869 vf00 | Diameter Overload Control for Charging Interfaces | Rel-15 |