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Implement the proven Online Charging System (OCS) to enable prepaid mobile services. In telecom billing, OCS is also known as Real-Time Charging or Prepaid Billing. Prepaid mobile services typically allow users to make calls and access mobile data using a SIM card. For prepaid services, customers pay in advance for a specific plan before they can begin using the service. Without this upfront payment (or a top-up), the service remains inactive. The OCS system is essential for offering and managing prepaid services.

What is an Online Charging System?

Online Charging System (OCS) provides real time charging to MNO, MVNO or Communication Service Providers to charge customers based on real time service usage

The OCS performs real-time calculations and makes decisions based on the customer’s available account balance and the account’s expiry date.

Managing the billing and revenue aspect of multiple subentities and subsidiaries is a daunting task for any business. Thus EarnBill brings you a unified and automated solution to overcome the challenges of multi-tenant invoicing so that you can focus on your core expertise and think of various business units and their product offerings to drive growth.

Which type of usages can be processed and charged by an OCS system?|OCS Billing System - Processed and Charged|OCS System Architecture

An Online Charging System (OCS) can manage charges for various types of telecom services, such as SMS, MMS, calls, mobile data, video, and API calls. These usage types can be categorized as either event-based or session-based.

For instance, SMS and MMS are event-based, as they do not involve an active user session. In contrast, calls and mobile data usage are session-based, as they involve an active user session that can last from a few seconds to several hours.

The OCS can be implemented in two ways, depending on the type of usage:

    1. Session-Based Charging
    2. Event-Based Charging

➡️ Session Based Charging

In Session-Based Charging, the network hardware component, such as the Universal Gateway (UGW), initiates a user session and continuously sends usage data through RADIUS or Diameter messages. Each session begins with an authentication message, followed by periodic usage updates that detail the actual usage—measured in minutes for calls and in bytes for data.

Online Charging System OCS

As illustrated in the diagram above, during session-based charging, the customer’s account balance is validated in real-time, allowing the user session—whether for calls or data usage—to continue if sufficient balance is available. The ongoing usage is continuously monitored at regular intervals through RADIUS messages, with the balance being checked in real-time. Upon the conclusion of the user session, the Call Data Record (CDR) or Usage Detail Record (UDR) is securely saved to the database within the OCS platform.

➡️ Event Based Charging

In Event-Based Charging, the Call Data Record (CDR) event is transmitted to the billing system after the event has taken place. In this scenario, the initial message from RADIUS is processed to verify whether the customer’s account has sufficient balance. The response to this message may also include information regarding the total units available for the user to consume. The final charging event may be triggered by the network component after the event has occurred.

What does an Online Charging System do?|How does an Online Charging System work?|What are the functions of an Online Charging System?

The Online Charging System interfaces with a network component of a Telecom Operator. This network component is a piece of equipment (hardware) and some software. In many cases, the Telecom Operators use the Universal Gateway (or a UGW offered by various providers). The UGW captures the request for usage made by the subscribers, and passes it to the Online Charging System.

Typically, OCS validates the following 3 things:

    • The subscriber’s available balance.
    • Usage quota made available on the plan.
    • The recharge expiry date.

If OCS finds that all 3 checks are passing, it responds back to the UGW (or a similar network component) confirming that the usage of the particular service can continue as there is sufficient balance or quota present for that subscriber.

The subscriber must start his or her prepaid services by buying the subscription with Telecom operator. This is done by purchasing a new plan, the SIM and making a payment of the fees involved as a top up transaction. Many Telecom Operators also support the concept of a Wallet.

What is a Wallet and a top-up transaction?

A Wallet is nothing more than a virtual account maintained by the subscriber with the Telecom Operator. The top-up transaction increases the Wallet balance, whereas the allocation of a prepaid plan by the Telecom Operator reduces the Wallet balance (marking that balance as consumed). An automatic renewal of the plan can take place at the end of the cycle (typically monthly) by deducting the available balance from the Wallet. The auto renewal will fail if there is insufficient balance in the wallet, resulting in the service being disconnected. The service will be able to be restarted once a new recharge has been made.

How does the Online Charging System (OCS) function?

The Online Charging System or OCS is implemented by using a software (listener component) which listens to specific requests originating from either a diameter client or a radius client. Each diameter or radius message emanating from the client (or the UGW) is picked up by the Diameter or a Radius Server implemented within the OCS. This post is written considering Radius protocol rather than Diameter, however similar concepts apply with Diameter with some differences.

The radius message could be of 4 types:

      • An Access Request,
      • An Accounting Start Request,
      • An Accounting Intermediate Update Request, and
      • An Accounting Close Request

➡️ Access Request

    • The UGW system creates a user session and requests for Authentication to the triple A (AAA) system in case of Diameter implementation. In case of Radius implementation, the OCS platform can provide the authentication response by verifying the authenticity of the access request.

➡️ Accounting Start Request

When the access request has been accepted by the radius server (or the OCS), then the UGW gets a confirmation that the usage can now start for the particular subscriber and service.

When the usage starts, the UGW sends an Accounting Start request to the Radius server (or OCS) indicating that the usage session has been started. The Radius server or OCS receives the Accounting Start Request and responds to it in affirmative in there is sufficient quota for the subscriber to continue with the service. There might be usage consumption minutes or bytes on the Account Start Request or not, it depends on the usage.

➡️ Accounting Intermediate Update Request

Once the Accounting Start Request is responded in the affirmative by the OCS, the next requests will be that of intermediate update. The session update requests are sent periodically by the UGW to the OCS as long as the user session (a call or a data usage session) is on. The update request will be processed by updating the usage quota or the subscriber balance.The update requests are periodical and recurring during the course of the call or data session.

For example, they may recur every minute or every 5 minutes or when the usage exceeds certain limit. In case of data session, the interim radius message could occur every 5 mins or after utilising 50 MB of data, whichever is earlier.

➡️ Accounting Close Request

An Accounting Close Request indicates that the subscriber has closed the usage session and the OCS marks session as ‘invalidated’. Then the next user session will be expected to be with another session id.

The EarnBill’s OCS platform supports both session based and event based charging. The system can be easily customised to meet unique needs of Telecom companies.

EarnBill Support Diameter Protocol|Radius Protocol with OCS Platform

EarnBill supports both the Diameter protocol as well as the Radius protocol while accepting messages emanating from a triple A (AAA) system (which stands for Authentication, Authorization and Accounting). EarnBill’s OCS platform also has the ability to replace the triple A system (AAA) by supporting the authentication and authorization, and then processing the message with the billing system to validate the usage quota.

There is a good amount of flexibility while integrating EarnBill’s OCS system into your application ecosystem. Whether the OCS system will play the role of AAA + OCS or just OCS system really depends on your existing or planned application + network infrastructure.