Offline Charging and Online Charging

Charging is enabled for a session based on the input that is received from the PCF.

For offline charging, the SMF sends Charging Data Request Initial toward the Charging Function (CHF) based on the presence of charging descriptors and refChgData field set in the smPolicyDecision message from the PCF in the SM Policy Control Create response.

On determining if charging is required during initial session establishment or post-session establishment, charging is enabled for the PDU session. Once charging is enabled, SMF sends the Charging Data Request (Initial) Message toward the CHF.

The SMF determines the Volume/Time threshold value either locally or from the Charging Data Response. These values are used to update the Volume/Time threshold IE in URR and to set the reporting trigger accordingly. The measurement method that is used in URR is derived from charging data.

For online charging, the SMF receives the Volume/Time Threshold and Quota values from the CHF. These values are received in the Charging Data Response (Initial) or using a Charging Data Request (Update) during a PDU Session Establishment. The SMF relays these Volume/Time Threshold and quota values to the UPF in the corresponding URR.

If Gy is enabled for an SMF 4G session, the session SMF sends the Credit Control Request (Initial) towards OCS to get the Volume/Time threshold and quota values. SMF relays these values towards to the UPF in the corresponding URR. If the SMF doesn't receive the volume threshold from OCS, the SMF determines the volume threshold from the local configuration.

Note

The threshold values from CHF always override the locally configured values.

The following table maps the IEs that are shared with the UPF during Create or Update URR during online or offline charging scenarios:

IE Mapping for Online and Offline Charging Scenarios
IE Online Offline Derived From (N40)

Derived From (Gy)

Volume Limit Yes Yes CHF Response or Local Configuration

OCS Response or Local Configuration

Time Limit Yes Yes CHF Response or Local Configuration

OCS Response

Volume Quota Yes No CHF Response

OCS Response

Time Quota Yes No CHF Response

OCS Response

Quota Holding Time Yes CHF Response

OCS Response

Monitoring Time Yes Yes
  • Local configuration for offline charging

  • CHF response for online charging

OCS Response or Local Configuration

Reporting Trigger Yes Yes The respective triggers that are set as shown in the following table.

OCS Response or Local Configuration

Validity Time

Yes

-

-

OCS Response or Local Configuration

The following table lists the reporting triggers and their derived source:

Reporting Triggers and the Derived Source
Reporting Trigger Derived From
Volume Threshold Trigger If Volume threshold is set
Time Threshold Trigger If Time threshold is set
Volume Quota Trigger If Quota Exhausted trigger is set from CHF
Time Quota Trigger If Quota Exhausted trigger is set from CHF
Linked Usage Reporting (LIUSA) Trigger If URR contains Linked URR