5 VCS charging principles and scenarios
32.2763GPPCharging managementRelease 17Telecommunication managementTSVoice Call Service (VCS) charging
5.1 VCS charging principles
The charging functions specified for VCS charging relate to:
– mobile originating calls;
– mobile terminating calls;
– mobile forwarded calls.
5.2 VCS charging – Offline charging scenarios
5.2.1 Basic principles
Not specified in the present document.
5.2.2 Rf message flows
Not specified in the present document.
5.2.3 CDR generation
Not specified in the present document.
5.2.4 Ga record transfer flows
Not specified in the present document.
5.2.5 Bx CDR file transfer
Not specified in the present document.
5.3 VCS charging – Online charging scenarios
5.3.1 Basic principles
VCS online charging may be performed by the Proxy Function using the common Debit / Reserve Units operation specified in TS 32.299 [50]. The Proxy Function shall be able to perform online charging for the following:
– charging information related to voice calls;
Session based online charging (SCUR) with centralized rating and centralized unit determination is required in the Proxy Function. The Debit/ Reserve Units Request and Debit / Reserve Units Response messages are specified for SCUR in TS 32.299 [50]. The Debit / Reserve Units Request messages are issued towards the OCS when certain conditions (chargeable events) are met and Debit / Reserve Units Response messages are received from the OCS in response. The VCS charging specific contents and purpose of each of these messages, as well as the chargeable events that trigger them, are described in the following subclauses. A detailed formal description of the online charging parameters defined in the present document can be found in TS 32.299 [50]. Further information on the general principles of the common 3GPP online charging application can also be found in TS 32.299 [50] and TS 32.240 [1].
Since an operator is able to determine if charging is started at three different points in the progress of a voice call: call attempt, called party alerting, or called party answer, a configuration option is defined in the Proxy Function for this determination. On the Diameter interface, as defined below, the OCS is contacted on call attempt. This allows the OCS to identify the user account status and authorize (or not) the voice call attempt prior to utilizing network resources to transport the call. At this time, a quota is also requested. The Proxy Function starts depleting the quota at the configured point progress of the call. The time this occurs is stored as the start of charging time delivered in the next update Debit / Reserve Units Request message to the OCS.
The following chargeable events are defined for VCS charging:
– Voice call attempt. Upon encountering this event, an initial Debit / Reserve Units Request message, indicating the start of the voice call, is sent towards the OCS to authorize the voice call attempt. The Proxy Function requests quota for voice call, setting the service-identifier to the value representing the type of voice call to be charged. Depending on operator configuration, the Proxy Function shall begin quota deduction and store the current time as start of charging time.
– Voice call answered. No message is sent. Depending on operator configuration, the Proxy Function shall begin quota deduction and save the current time as start of charging time.
– Voice call not answered – MO/MF only (e.g., busy, no answer, not reachable, route select failure). Upon encountering this event, corresponding counts for the voice call are closed and a terminate Debit / Reserve Units Request message, indicating the end of the voice call, is triggered. If the operator configuration has indicated that charging has started prior to answer, the start of charging time is provided with the used service units.
– Voice call not answered and call is conditionally forwarded – MT only (e.g., call forwarding on not reachable). Corresponding counts for the voice call are closed and an update Debit / Reserve Units Request message is triggered. If the operator configuration has indicated that charging has started prior to answer, the start of charging time is provided with the used service units. The subsequent response indicates if charging for terminating leg is to be maintained.
– Voice call not answered and call is not conditionally forwarded – MT only (e.g., busy, no answer, not reachable, route select failure). Upon encountering this event, corresponding counts for the voice call are closed and a termination Debit / Reserve Units Request message, indicating the end of the voice call, is triggered. If the operator configuration has indicated that charging has started prior to answer, the start of charging time is provided with the used service units.
– End of voice call. Upon encountering this event, a terminate Debit / Reserve Units Request message, indicating the end of the voice call, is sent towards the OCS together with the final counts. The start of charging time is provided with the used service units.
– Ro specific chargeable events (e.g. threshold reached, quota exhaustion, validity time reached, forced re-authorization). Corresponding counts for the voice call are closed and an update Debit / Reserve Units Request message is triggered according the rules defined in TS 32.299 [50].
– Change of charging condition: E.g. user location change. When this event is encountered and the corresponding re-authorization trigger is armed, all current counts are captured and sent towards the OCS with an update Debit and Reserve Units Request message.
Editors’s note: The encounter of this event in conjunction with the ability of the Trigger AVP is ffs.
– Tariff time change. When this event is encountered, all current counts are captured and a new counts are started. The counts are sent to the OCS in next Debit and Reserve Units Request message.
Management intervention may also force trigger a chargeable event.
The OCS online charging function may use the Furnish Charging Information procedure to add online charging session specific information to the CDR generated by the MSC as currently supported for CAMEL as specified in TS 23.078 [207]
In case the OCS fails, the Proxy Function shall support the Failure Handling procedure and Failover mechanism described in TS 32.299 [50]. These mechanisms give flexibility to have different failure handling scenarios when the OCS fails.
Three different actions shall be supported when the failure handling mechanism is executed:
– Terminate: The online session is finished. The associated voice call is terminated (answered calls) or not established (new calls). Failover for ongoing voice calls is not supported. Failover for new voice calls is always supported.
– Retry&Terminate: The online session is finished. The associated voice call is terminated (answered calls) or not established (new calls). Failover for ongoing voice calls is supported. Failover for new voice calls is always supported.
– Continue: The online session is finished. The associated voice call is established (new calls) or not terminated (ongoing calls). Failover for ongoing voice calls is supported. Failover for new voice calls is always supported. It shall be operator configurable to limit the maximum duration of the voice call in this situation.
The OCS may request session re-authorization of active quota.
The OCS may request service termination synchronously in response to a Reserve Units Request or asynchronously via Diameter Abort-Session-Request. In either case, the voice Proxy Function shall initiate termination of the voice call using CAMEL procedures, as specified in TS 23.078 [207].
The OCS may specify a termination action, as per TS 32.299 [50] clause 5.3.3 and clause 6.5.3, for the voice Proxy Function on consumption of the final granted units. The only action supported is TERMINATE.
The following capabilities defined in TS 32.299 [50] are not applicable to VCS charging:
– Credit pooling
– Envelope reporting
– Online control of offline charging information
– Support of multiple service
NOTE: The Multiple Operation and Multiple Unit Operation information elements are utilized as per Table 6.2.2.1. Only one service is supported per VCS charging session.
5.3.2 Ro message flows
5.3.2.1 Ro messages
An initial, update and terminate Debit and Reserve Units Request message, as defined in TS 32.299 [50], is used by the Proxy Function to transfer the collected charging information towards the OCS. The Debit and Reserve Units Response message is used by the OCS to assign quotas for the service identifier, and to instruct the Proxy Function whether to continue or terminate a voice call.
The following clauses describe the trigger conditions for the chargeable events described in clause 5.3.1. These chargeable events correspond to the triggers for collection of charging information and Debit and Reserve Units Request message transmission towards the OCS. The responses from the OCS are also specified in the clauses below.
5.3.2.2 Triggers for starting and stopping a VCS credit control session
A initial Debit and Reserve Units Request is sent to OCS when a voice call is attempted.
A terminate Debit and Reserve Units Request is sent to OCS when:
– voice call is not answered (MO/MF)
– voice call not answered and not conditionally forwarded (MT)
– voice call is terminated
– voice call termination is indicated by the OCS (e.g. Credit Limit Reached)
– Abort-Session-Request is received from the OCS, this also results in voice call termination.
5.3.2.3 Triggers for providing interim information for a VCS credit control session
An update Debit / Reserve Units Request is sent to OCS when:
– Voice call not answered and call is conditionally forwarded (MT) ;
– Granted quota runs out;
– Validity time for granted quota expires;
– Update is requested by the OCS;
– Change of charging conditions occur and according to re-authorisation trigger, re-authorisation is needed;
– Management intervention.
5.3.2.4 Furnish Charging Information procedure
The OCS online charging function may use this procedure to add online charging session specific information to the CDR maintained by the originating MSC by means of the Debit and Reserve Units Request operation. The Furnish Charging Information can be sent either in one Debit and Reserve Units Response message or several Debit and Reserve Units Response messages with append indicator.
The OCS online charging function can send multiple concatenated Furnish Charging Information elements per online charging session.
The total maximum of free format data Furnish Charging Information is 160 octets.
5.3.2.5 Support of Failure Situations
In case the OCS fails the Proxy Function must support the Failure Handling procedure and Failover mechanism described in TS 32.299 [50].
According to TS 32.299 [50], timer Tx determines the maximum interval the Proxy Function shall wait for an answer to each credit control request sent to the OCS. When Tx expires, Proxy Function shall execute the Failover and Failure Handling mechanisms according to the behaviour described in TS 32.299 [50].
Three different actions shall be supported when the failure handling mechanism is executed:
– Terminate: The online session is finished. The associated voice call is terminated (answered calls) or not established (new calls). Failover for ongoing voice calls is not supported. Failover for new voice calls is always supported.
– Retry&Terminate: The online session is finished. The associated voice call is terminated (answered calls) or not established (new calls). Failover for ongoing voice calls is supported. Failover for new voice calls is always supported.
– Continue: The online session is finished. The associated voice call is established (new calls) or not terminated (ongoing calls). Failover for ongoing voice calls is supported. Failover for new voice calls is always supported. It shall be operator configurable to limit the maximum duration of the voice call in this situation.