How real-time charging works: balances, reservations, free units, vouchers and the notifications that keep subscribers informed.
Online charging decides, before or during a call, data session or purchase, whether a subscriber may use a service and how much it costs. The network asks the charging system for permission, the charging system reserves part of a balance, and the network reports what was actually used. Prepaid is the classic example, but modern converged charging applies the same real-time control to postpaid plans, shared allowances and enterprise spending caps.
Offline charging, by contrast, collects usage records after the event and rates them later in batch. Most operators now run one converged charging engine for both, so that a bundle, a discount or a spending limit behaves the same way whatever the payment type.
The reserve, use and report cycle used by every real-time charging protocol.
The packet core asks the charging system to authorise a new data session for the subscriber.
The rating engine finds the applicable tariff and reserves a quota, for example 50 MB or 10 minutes, from the right bucket.
The quota is granted with a validity time; the network lets traffic flow.
When the quota is nearly used, the network reports usage and asks for more. Unused reservation is returned.
When balances run out, the network is told to redirect to a top-up page, throttle or stop.
Final usage is reported, the balance is debited and a charging record is written for billing and analytics.
The main concepts every online charging system has to model.
Monetary balances, unit buckets (MB, minutes, SMS) and counters, each with its own validity, priority and rollover rules.
Rules that decide which bucket is used first: free units, then bundle allowance, then main balance.
Voucher generation, activation and redemption, plus top-ups from cards, wallets and retailers, with fraud controls on failed attempts.
Daily, monthly or per-service caps for consumers, children's lines and enterprise users, enforced in real time.
Threshold alerts such as 80% used, low balance or bundle expired, sent by SMS, push or USSD.
Account states such as active, grace, suspended and recycled, driven by balance expiry and inactivity.
| Online (real time) | Offline (batch) | |
|---|---|---|
| When rated | During the event | After the event |
| Credit control | Yes: can block or redirect | No: usage is billed later |
| Typical use | Prepaid, caps, shared allowances | Postpaid usage, wholesale, interconnect |
| Interfaces | Diameter Ro/Gy, 5G Nchf | Diameter Rf/Ga, charging data records |
Charging is rich in real-time data, which makes it a natural place for machine learning.
Predict when a prepaid subscriber is about to run out and offer the right top-up or bundle at the right moment.
Spot voucher abuse, SIM-box traffic and unusual spending patterns in near real time.
Detect rises in charging failures or latency before they become customer-visible outages.
This page describes generic industry practice and public standards. It is not based on, and does not describe, any particular vendor's product or operator's systems.