Telecom Charging in a 5G Network

 5G Converged Charging at a glance by Rajarshi Pathak


Telecom Charging Basics: In my previous articles, I have explained in-depth the concepts of Online Charging and Offline Charging in the Telecom domain.

To know more about Online Charging, please read Basics of Telecom Online Charging.

To know more about Offline Charging, please read Basics of Telecom Offline Charging.

Here, is the summarized version of Online & Offline Charging Concepts: -

For Online Charging, the balance reservation/deduction happens before the consumption of the Services from the Credit balance. For Subscribers to use Services, it is required for them to have enough balance in their account.

For Offline Charging, the balance update or redemption happens after the consumption of the Services and normally, the usage charges appear on the Invoice/Bill of the Subscribers. As long as, Subscribers are not reaching their credit limit, they can consume the Services and keep on paying the bills.

I would encourage you to read the mentioned articles in case the summary is not enough.

Coming back to the topic of Telecom Charging in a 5G World.

Telecom Charging in 5G will be Converged Charging, meaning, it will support both Online as well as Offline Charging models.

Converged Charging by Rajarshi Pathak

fig. Converged Charging

It is on the same line as Converged Billing System, which can handle Postpaid as well as Prepaid Payment methods and process Online Charging as well as, Offline Charging events.

The functioning of 5G Convergent Charging System: -

5G Converged Charging, Rating, and Billing in a nutshell

fig. 5G Converged Charging, Rating, and Billing in a nutshell


How Online Charging Triggers are processed by 5G Converged Charging System:

  • Customer initiates service usage.
  • Receives Online Charging trigger from the Network.
  • Performs Service Authorization and Credit control.
  • Measures the event & performs the required balance reservations.
  • For Session based charging, Service Operations like Create, Update & Release are performed just like Initial, Update & Terminate Diameter Messages in a 3G/4G world. Via this, ConvergedCharging Operation allows Service delivery of Session-based Services with or without Quota Management.

CTF (SMF, SMSF, AMF, NEF/AF acting as NF Consumers) to demand Requested Service Units from CHF, CHF acknowledgement by Granted Service Units to CTF and later CTF updates back the Used Service Units to CHF.

  • For Event based charging, ConvergedCharging Service allows Service delivery. NF Consumer to demand Requested Service Units from CHF and CHF acknowledgement by Granted Service Units to CTF through Charging Data Request [Event] & Charging Data Response [Event].
  • On Service Termination, apply balance impacts to the measured event based on Rating & Pricing configuration.
  • Rated Event data gets generated and stored in the Billing system.

How Offline Charging Records are processed by 5G Converged Charging System:

  • Customer initiates service usage.
  • Raw CDRs get generated about this usage. Usage can be Session-based (e.g. HD Voice call, Multimedia Session, etc.) or Event-based (e.g. IOT Sensors Events, SMS, etc.). OfflineOnlyCharging Service Operations are used for Session-based Services and ConvergedCharging Service Operations are used for Event-based Services.
  • Charging Data Request and Charging Data Response Messages between CHF & CTF (SMF acting as NF Consumer) are used to construct CDRs for service usage. Operations like Create CDR, Open CDR, Update CDR and Close CDR are performed via the APIs.
  • Raw CDRs are collected and processed.
  • Processed CDRs based on enrichment & business rules are guided to Rating Engine.
  • CDRs are rated by Rating Engine as per the rate plans by measuring the events.
  • Rated Event data gets generated and stored in the Billing system.
 Interworking of 5G Charging System with Policy Control:

Along with the above, CHF works together with PCF for Spending Limit Control by monitoring the Subscriber's Usage consumption & Policy Counters by interacting with PCF. Together with PCF, it provides Policy and Charging Control during service delivery.

In case you wish you get extensive details, you can read my previous article Policy and Charging Control in a 5G Network

Let's understand the 5G Converged Charging Server mechanism as per 3GPP standard: -

Below figure explains the 5G Converged Charging architecture as per the 3GPP standard.

5G Converged Charging Architecture

fig. 5G Converged Charging Architecture

CTF (Charging Trigger Function): This is the node in the network which generates charging triggers whenever a Customer uses services. Let's suppose, a Customer wants to send an SMS. Here, the SMSF node acts a CTF and generates charging triggers for SMS delivery.

CHF (CHarging Function): CHF is an integral entity in CCS (Converged Charging System) which provides Account Balance Management function (ABMF) for balance management/quota management, Rating Function (RF) for measuring the events and Charging Gateway Function (CGF). Together, they are known as Converged Charging Server (CCS).

If compared with 4G Network, CHF combines the functionality of OCF (Online Charging Function) and CDF (Charging Data Function). Hence, CHF enables Online and Offline Charging by closely interfacing with NF Consumers.

CGF (Charging Gateway Function): It Collects, Validates, Parse & Enriches the Raw CDRs and Distributes the processed CDRs to the BSS systems.

Billing System: This is the core system of the Operators' BSS stack. It consumes the rated events stored in the database and adds up the Usage charges against the Customer's bill amount. During Bill Run, charges like monthly recurring charges, one-time charges, cancellation charges, etc. are processed along with usage charges. Other activities like billing time discounts, adjustments, settlements, taxes, etc. are also considered during the Bill Run. Once the Bill is finalized, it becomes ready for Payments against the Invoice.

Below is the simplified view of CHF and associated Network Functions in a typical 5G Network Architecture: -

A simplified view of CHF in a 5G Network

fig. A simplified view of CHF in a 5G Network

As explained above, Converged Charging Server takes care of processing Online & Offline Charging records by working with NF Consumers like SMF, SMSF, AF, etc. and updating rated events into the Billing System. It also interacts with PCF for Policy & Charging Control.

Towards the end…

5G Charging System should be capable to charge customers/enterprises based on the Services consumed through different Network slices.

It should be Cloud-enabled for the required Auto-scaling & flexibility for high-volume usage processing. Along with the RESTful APIs support, it should also be backward compatible with Diameter & CAMEL charging protocols as well.

5G Charging System is expected to support charging for Use cases related to eMBB, mMTC and URLLC Services. This requires Usage Processing based on high bandwidth (e.g. FWA, 4K/8K content delivery), low latency/high threshold (e.g. AR/VR, Self-driving cars) and high density (e.g. IoT devices, Smart Cities, Industry 4.0) Service consumptions.

5G Network caters to B2C, B2B and B2B2X business models and hence, the Charging requirements may vary based on the business use cases for Consumers, Enterprises and Partners.

The road to explore the full potential of the 5G Monetization Solution will be quite interesting!

To know more about 5G Charging System Requirements, please read Requirements for the 5G Monetization Solution

Kindly share this article with your friends and colleagues. Feel free to like and comment. Happy learning.


Glossary:  3GPP (3rd Generation Partnership Project), BSS (Business Support System), OSS (Operations Support System), SBI (Service based Interface), CHF (Charging Function), CCS (Converged Charging Service/System), SMF (Session Management Function), NF (Network Function), SMSF (Short Message Service Function), Nchf (CHF Service Based Interface), PCF (Policy Control Function), AMF (Access and Mobility Management Function), NEF (Network Exposure Function), UE (User Equipment), AF (Application Function), AAA (Authentication, Authorization & Accounting Server), eMBB (enhanced Mobile Broadband), URLLC (Ultra-Reliable Low Latency Communications), mMTC (massive Machine Type Communications), FWA (Fixed Wireless Access), CAMEL (Customized Applications for Mobile network Enhanced Logic)

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