5.1 5G data connectivity charging principles
32.2553GPP5G data connectivity domain chargingCharging managementRelease 17Stage 2Telecommunication managementTS
5.1.1 General
The charging functions specified for the 5G data connectivity charging:
– PDU session in SMF, refer to TS 23.501 [200];
– service data flows, within PDU session, refer to TS 23.503 [202].
– QoS flows within PDU session refer to TS 23.501 [200] and TS 23.503 [202].
5.1.2 Requirements
The following are high-level charging requirements specific to the packet domain, derived from the requirements in TS 22.115 [101], TS 22.261 [102], TS 23.501 [200], TS 23.502 [201] and TS 23.503 [202].
– The SMF shall support converged online and offline charging.
– The SMF may support offline only charging.
– The SMF shall support PDU session charging using service based interface.
– The SMF shall support network slice instance charging.
– The SMF shall collect charging information per PDU session for UEs served under 3GPP access and non-3GPP access (untrusted non-3GPP access, trusted non-3GPP access and wireline).
– Every PDU session shall be assigned a unique identity number for billing purposes per PLMN. (i.e. the Charging Id).
– Data volumes on both the uplink and downlink directions shall be counted separately. The data volumes shall reflect the data as delivered to and forwarded from the user.
– The charging mechanisms shall provide the date and time information when the PDU session starts.
– The SMF shall be capable of handling the Charging Characteristics. Charging Characteristics can be specific to a subscription or subscribed DNN.
– The SMF may be capable of identifying data volumes, elapsed time or events for individual service data flows (flow based charging). One PCC rule identifies one service data flow.
– SMF shall allow reporting of the service or the detected application usage per rating group or per combination of the rating group and service id. This reporting level can be activated per PCC rule.
– The quota management shall be per rating group per PDU session.
– If there are multiple UPFs for one PDU session, the quota management may be one for all UPFs or separate per UPF and the usage and charging information reporting per UPF.
– The SMF shall support charging for PDU Session types of IP, Ethernet and Unstructured.
– In Home Routed scenario, the SMF shall collect charging information per PDU session and, based on Home Operator policy and agreement between Home and Visit Operators, shall be able to collect charging information per Qos Flow for in-bound and out-bound roamers in Home Routed scenario.
– In Local breakout scenarios, the SMF in VPLMN shall collect charging information per QoS flow and, based on Visited Operator policy and agreement between Home and Visit Operator, may be able to collect charging information per service data flow for roamers in the LBO scenario.
– For interworking between 5GS and EPC, the dedicated PGW-C + SMF shall collect charging information using the same mechanisms as the SMF.
– The SMF shall support PDU session charging when the PDU session is served by both I-SMF and SMF.
– The SMF shall support charging for MA PDU Connectivity Service over 3GPP access and non-3GPP access.
– The SMF in VPLMN and in HPLMN shall support charging for MA PDU Connectivity Service in roaming Home Routed scenario with UE registered to the same VPLMN for 3GPP access and non-3GPP access.
– The SMF in HPLMN shall support charging for MA PDU Connectivity Service in roaming Home Routed scenario with UE registered in different PLMNs.
– The SMF shall support the charging of redundant transmission for high reliability communication.
– The SMF shall support the charging of 5G LAN VN group communication.
– The SMF shall support the charging of 5GS CIoT.
5.1.3 Charging information
Charging information in the 5GC domain network is collected for each UE by the SMFs. PDU session charging allows the SMF to collect and categorize per UE per UPF per PDU session, charging information related to data volumes.
The SMF shall collect the following charging information for converged online and offline charging:
– usage of the access and core network resources: the charging information shall describe the amount of data delivered to and forwarded from the UE;
– usage duration: duration of PDU session is counted as the time interval from PDU session establishment to PDU session release;
– user: the charging information shall provide the actual UE addresses used by the user for the PDU session;
– data network: the charging information shall describe the data network addresses with a level of accuracy as determined by the DNN;
– usage of the external data networks: the charging information shall describe the amount of data sent and received to and from the external data network. External networks can be identified by the DNN;
– start time: identifying the time when the PDU session was started;
– user location: HPLMN, VPLMN, inside/outside presence reporting area, plus optional higher-accuracy location information.
The service data flows categorization is achieved by rating group or combination of the rating group and service id: i.e. based on the level of reporting defined per PCC rule, counting per rating group or combination of the rating group and service id. According to TS 23.503 [202], flow based charging shall support different charging models per PCC rule. These charging models may be based on volume, time and/or on number of events matching a specific service data flow template in PCC rule.
For service data flows defined for FBC, the SMF shall collect the following charging information:
– the information described above for PDU session;
– the amount of data transmitted in uplink and downlink directions categorized by rating group or combination of the rating group and service id when volume based charging applies;
– the duration of service data flows is counted and categorized by rating group or combination of the rating group and service id when time based charging applies;
– the number of events and corresponding time stamps categorized by rating group or combination of the rating group and service id when event based charging applies.
Within the PDU session the SMF shall collect the charging information for service data flows per UPF, categorized by rating group or combination of the rating group and service id.
Within the PDU session for local traffic offload scenarios with I-SMF insertion, the SMF shall collect the charging information for service data flows per I-SMF and categorized by rating group or combination of the rating group and service id.
Editor’s note: To have I-UPF as well as PSA2 UPF for the I-SMF controlled UPF is FFS.
The user can be identified by a Generic Public Subscription Identifier (GPSI) and/or a 5G Subscription Permanent Identifier (SUPI). For wireline access, SUPI may be used to identify subscriber via wireline network as specified in clause 5.9.2 of TS 23.501 [200].
5.1.4 Charging Identifier
Charging identifier is created to allow correlation of charging information.
For the SMF the charging identifier is assigned per PDU session including the case of I-SMF insertion. At each PDU session establishment, i.e. assignment of a new PDU session id, a new PDU session specific SMF Charging Identifier is generated at the first SMF that processes the PDU session initiating request. The SMF Charging Identifier shall be unique within the SMF (that means that the charging identifier is unique within the SMF set if SMF set is used) which assigned it and is then used in all subsequent messages for that PDU session. The Charging Identifier shall be used throughout the PDU session’s lifetime once assigned. In case of inter-system changes or handovers of PDU session, the Charging Identifier is preserved as long as the PDU session Identifier is preserved.
For EPS handover 5GS in Home routed scenario, the Charging Identifier for the EPS PDN connection will be generated by PGW-C+SMF in HPLMN and transferred to the SMF in VPLMN, if the V-SMF has already generated the Charging Identifier, the value shall be replaced by Home Provided Charging Id generated by H-SMF.
For 5GS interworking with EPS, an "EPS bearer Charging Id" is assigned by the PGW-C+SMF to each dedicated EPS bearer The "EPS default bearer Charging Id" is the "Charging Id" assigned to the default bearer of PDU connection.
For mobility from HPLMN with I-SMF to VPLMN in Home routed scenario, the Charging Identifier for the PDU session will be generated by SMF in HPLMN and transferred to the SMF in VPLMN, if the V-SMF has already generated the Charging Identifier, the value shall be replaced by Home Provided Charging Id generated by H-SMF.
5.1.5 PCC rules and charging
5.1.5.1 PCC rules and chargeable events
PCC rules can be activated, deactivated and modified at any time during the PDU session lifetime. The following attribute can be modified by the PCF in a dynamic PCC rule active in the SMF: Charging key, Service identifier, Sponsor Identifier, Application Service Provider Identifier, Measurement method and reporting level. The QoS Flow binding mechanism employed by the SMF upon operations on PCC rules, may result in QoS Flows establishment, modification, or release. This is specified in TS 23.503 [202].
Activities on PCC rules are not chargeable events. However, change of charging rule in PCC rules will lead to chargeable events "start of service data flow" and when this is the last service data flow for the original PCC rule, "termination of service data flow".
The charging key (i.e. Rating group) is a piece of information used to request online charging quotas as defined in TS 23.503 [202].
5.1.5.2 Specific PCC rules scenarios
The capability of SMF to support Application Based Charging is achieved with appropriate PCC rules activation in the SMF. Such PCC Rule shall be defined with service data flow template including an Application Identifier for the application which needs to be detected, enforced and charged. Application detection mechanism in SMF is defined in TS 23.503 [202].
5.1.5.3 PCC rules – MA PDU session
As specified with PCC Rule definition in clause 6.3.1 TS 23.503 [202], during MA PDU session handling by the SMF, PCC Rules can be activated with a MA PDU session control information attribute including an optional rating group for Non-3GPP access, in addition to the rating group included in the PCC rule description.
When the MA PDU session control information in a PCC Rule includes a separate rating group for Non-3GPP access, it shall be used by the SMF for the SDF traffic carried via non-3GPP access. The PCC Rule rating group shall be used for the SDF traffic carried via 3GPP access, and all other charging related attributes in the PCC rule shall be the used for both accesses.
When the MA PDU session control information in a PCC Rule does not include any rating group for Non-3GPP access, the PCC Rule rating group shall be used by the SMF for the SDF traffic carried via both accesses (i.e. 3GPP access and non-3GPP access).
5.1.6 Session and Service Continuity modes
For any scenario of SSC modes specified in TS 23.501 [200], one charging Id shall correspond to a single PDU session ID.
As a result from such SSC mode, a new charging Id is generated by the SMF for the new PDU session Id, and the charging session associated to the old PDU session Id is released.
This behaviour applies to the following scenario:
– PDU session anchor UPF relocation, in SSC mode 2;
– PDU session anchor UPF relocation in SSC mode 3 with multiple PDU Sessions.
5.1.7 UE Presence in Presence Reporting Area (PRA)
During charging session lifetime, the CHF may provide the Presence Reporting Area identifier to be activated for Core Network pre-configured Presence Reporting Area(s) and additionally all of PRA Identifier(s) and list(s) of its elements for UE-dedicated Presence Reporting Area(s) and provision the "Change of UE presence in Presence Reporting Area(s)" trigger to the SMF to request the reporting of Change of UE presence in Presence Reporting Area. After such trigger is enabled, SMF shall close the current count, open a new count with the initial status of UE presence in the PRA(s). In case of quota management is required, a Charging Data Response [Update] including the initial status is sent. UE presence status in the PRA(s) describes whether the UE is entering or leaving Presence Reporting Area (s) and if the corresponding Presence Reporting Area(s) is set to inactive by the serving node.
The CHF may modify the list of PRA Identifier(s) by providing the new Presence Reporting Area(s) or by removing existing Presence Reporting Area(s) or modify the list(s) of Presence Reporting Area elements by providing the updated Presence Reporting Area.
The CHF may remove the trigger of change of UE presence in Presence Reporting Area as defined in subclause 5.2.1.2, if previously activated.
5.1.8 CHF selection
The CHF selection by the SMF is done at the PDU session establishment, this selection shall be based on the following and with this priority order (highest to lowest):
– CHF address(es) with possible associated CHF instance ID(s) and/or CHF set ID(s) provided by the PCF for the PDU session.
– UDM provided charging characteristics.
– NRF based discovery.
– SMF locally provisioned charging characteristics.
This means that if there are PCF provided CHF address(es) with possible associated CHF instance ID(s) and/or CHF set ID(s) these shall be used, otherwise if the UDM provides charging characteristics these shall be used. If neither of these results in CHF address(es) the NRF can be used to discover CHF instance(s) possibly within a CHF set, and as a last resource the SMF locally provisioned charging characteristics shall be used.
When NRF is used for the CHF selection, and the PDU session charging method indicates "offline only" for the PDU session, CHF instance(s) supporting CHF "offline only" service instances may be selected.
5.1.9 Roaming
5.1.9.1 General
In home routed scenario, based on roaming agreements between the V-PLMN and the H-PLMN, for each UE roaming in VPLMN:
– The SMF in VPLMN (V-SMF) shall be able to collect charging information per QoS Flow within a PDU session when UE is determined as an in-bound roamer, for CDR generation in VPLMN.
– The SMF in HPLMN (H-SMF) shall be able to collect charging information per QoS Flow within a PDU session when UE is determined as an out-bound roamer, for CDR generation in HPLMN.
In home routed scenario, this charging information collection mechanism is achieved under Roaming QoS flow Based Charging (QBC) performed by each PLMN, based on a set of charging parameters exchanged between the V-SMF and the H-SMF on a per PDU session basis.
In home routed scenario, the main parameters exchanged at PDU session establishment are:
– The Charging Id assigned by the V-SMF and transferred to the H-SMF in the HPLMN.
– Optionally, the "Roaming Charging Profile" negotiated between the VPLMN and the HPLMN.
In home routed scenario, the parameters exchanged during the PDU session handover from EPS to 5GS:
– The Home Provided Charging Id which includes the Charging Id assigned by the H-SMF to the original PDU session over EPS and transferred by the H-SMF to the V-SMF. This Home Provided Charging Id shall be used by the V-SMF to replace the existing Charging Id previously generated by V-SMF.
– Optionally, the "Roaming Charging Profile" negotiated between the VPLMN and the HPLMN on 5GS side.
In roaming home routed PDU session, upon V-SMF change:
– intra-PLMN V-SMF change: Charging Id, "Roaming Charging Profile" and CHF address (optional) are transferred from the old V-SMF to the new V-SMF.
NOTE: how the new V-SMF selects the V-CHF is operator specific.
– inter-PLMN V-SMF change: The Charging Id is transferred from the old V-SMF to the new V-SMF.
– The "Roaming Charging Profile" is optionally exchanged between the new V-SMF and the H-SMF as for a PDU session establishment.
In local breakout scenario, based on roaming agreements between the V-PLMN and the H-PLMN, for each UE roaming in VPLMN:
– The SMF in VPLMN (V-SMF) shall be able to collect charging information within a PDU session when UE is determined as a roamer:
– per QoS flow for CDR generation by V-CHF in VPLMN and CDR generation by H-CHF in HPLMN;
– per service data flow for converged charging, based on PCC rules from V-PCF which uses locally configured policies according to the roaming agreement with the HPLMN operator, when applicable:
– with or without quota management to H-CHF in HPLMN;
– without quota management to V-CHF in VPLMN.
– The SMF in VPLMN (V-SMF) shall be able to determine applicable combinations based on operator policy.
In local breakout scenario, the main parameters exchanged at PDU session establishment are:
– The Charging Id assigned by the V-SMF and reported to the V-CHF and H-CHF.
– Optionally, for QBC, the "Roaming Charging Profile" is used for the set of triggers, associated category, and trigger thresholds and negotiated between the VPLMN and the HPLMN
In roaming Home routed PDU session, when an UE moves from HPLMN with I-SMF insertion to a VPLMN:
– The Home Provided Charging Id which includes the Charging Id assigned by the H-SMF to the original PDU session and transferred by the H-SMF to the V-SMF. This Home Provided Charging Id shall be used by the V-SMF to replace the existing Charging Id previously generated by V-SMF.
– Optionally, the "Roaming Charging Profile" negotiated between the VPLMN and the HPLMN.
5.1.9.2 CHF selection
In home routed scenario, at PDU session establishment, the CHF selection mechanism specified in clause 5.1.8 applies to:
– The V-SMF for CHF selection in VPLMN, with the following differences:
– CHF address(es) selection mechanisms based on PCF and UDM are not applicable.
– When charging characteristics is used it will be based on local configuration .
– When NRF is used, the V-CHF can be selected based on UE identified as in-bound roamer and the PLMN Id of the H-PLMN.
– The H-SMF for CHF selection in HPLMN can be done as for non-roaming case.
In roaming home routed, PDU session upon V-SMF change:
– Intra-PLMN V-SMF change: CHF address supplied by the old V-SMF shall be used.
– Inter-PLMN V-SMF change: CHF selection mechanism as per V-SMF CHF selection in VPLMN at PDU session establishment.
In local breakout scenario, at PDU session establishment, the CHF selection mechanism specified in clause 5.1.8 applies to:
– The V-SMF for CHF selection in VPLMN, is the same as in the home routed scenario.
– The V-SMF for CHF selection in HPLMN, with the following differences.
– CHF address(es) selection mechanisms based on PCF, UDM, and local configuration are not applicable.
– NRF based discovery, the H-CHF can be selected based on the H-PLMN of the UE.
5.1.10 Data Volume Reporting for Secondary RAT usage
Volume reporting for Secondary RAT usage is an optional capability in the SMF that provides usage reporting functionality when a Secondary RAT is used by NG-RAN. Use of Secondary RAT refers to options supported by NG-RAN with dual radio accesses, per NG-RAN definition in TS 23.501 [200]. This is valid for both HPLMN and VPLMN.
The following principles are used:
– The reporting of Secondary RAT Data Volume is controlled by the NG-RAN.
– The uplink and downlink data volumes for the Secondary RAT are reported (from NG-RAN to 5G Core) on a per QoS Flow basis and per time interval (controlled by NG-RAN). The report contains Secondary RAT (e.g. E-UTRA) resources used for transport of user data and indicated separately for uplink and downlink per QoS Flow and per time interval. The time interval used for the measurements reported (from NG-RAN) may be partitioned to indicate usage that occurred before respectively after an absolute time (that occurs while measurement for secondary RAT usage report is ongoing).
– The reporting (performed by NG-RAN) in association with UE-related control signaling and via standalone reporting is internally triggered by NG-RAN.
NOTE: Volumes for the secondary RAT are reported to the CHF in addition to, and uncorrelated from volumes of reported usage, which are undifferentiated between primary and secondary RAT. Considering both volumes would imply the same traffic to be counted twice.
5.1.11 Charging method and Charging service selection
A PDU session charging method indicating "offline only", can be assigned to a PDU session, to indicate a charging method applicable at PDU session level.
When there is no PDU session charging method indicating "offline only" associated to a PDU session, for each PCC Rule:
– if indicated for this PCC Rule, the required charging method applies;
– otherwise (i.e. no required charging method is indicated for this PCC Rule), the default charging method applies.
In this case, the converged charging service will be invoked by the SMF at the PDU session establishment.
When a PDU session charging method indicates "offline only" for a PDU session, offline charging method applies to all the PCC Rules activated during the PDU session. In this case, at the PDU session establishment, the SMF can select between the converged charging service or the offline only charging service based on Operator policy.
This PDU session charging method can be received from PCF by the SMF or configured in the SMF charging characteristics.
5.1.12 Emergency PDU session handling
Volume reporting for Emergency PDU Sessions is a capability in the SMF that provides usage reporting functionality when a session is setup to provide emergency services.
The following principles are used:
– The reporting of Emergency PDU sessions is controlled by the SMF.
– The uplink and downlink data volumes for Emergency PDU Session are reported.
– It includes either or both of an unauthenticated SUPI and a PEI (especially applicable in the case where there is a UE without a UICC).
5.1.13 Support of deployments topologies with specific SMF Service Areas
Depending on scenario, a PDU Session in non-roaming case is either served by a single SMF or served by an SMF and an I-SMF, specified in the clause 5.34 of TS 23.501 [200].When a PDU Session is served by both an SMF and an I-SMF, the SMF is the NF Consumer that has the interfaces towards CHF for I-SMF for the case of an I-SMF insertion, relocation or removal.
For the following case with the I-SMF involved, the SMF shall collect the charging information and report to CHF:
– PDU session establishment, modification and release;
– PDU Session message flows for N2 based handover procedure, with I-SMF insertion/change/removal;
– PDU Session message flows for Xn based handover procedure, with I-SMF insertion/change/removal;
– PDU Session message flows for Service Request, with I-SMF insertion/change/removal
– branching point or UL CL controlled by I-SMF.
5.1.14 Ultra Reliable Low Latency Communication
5.1.14.1 General
The enhancement of the 5GS to support Ultra Reliable Low Latency Communication (URLLC) is specified in the clause 5.33 of TS 23.501 [200]. For the redundant transmission for high reliability communication, the SMF shall collect the charging information for redundant transmission and report to CHF for the following cases.
– Dual Connectivity based end to end Redundant User Plane Paths;
– Redundant transmission on N3/N9 interfaces;
– Redundant transmission at transport layer.
5.1.14.2 Support redundant transmission for high reliability communication
The SMF reports the redundant transmission type to the CHF to indicate which redundant transmission type is used for the PDU session or service data flow.
For dual connectivity based end to end Redundant User Plane Paths, the charging information is collected independently per each redundant PDU session. The quota is granted for each redundant PDU session independently. The SMF reports the usage per redundant PDU session.
5.1.14.3 QoS Monitoring to Assist URLLC Service
For the QoS Monitoring to Assist URLLC Service, the SMF may report the packet delay measurement per QoS Flow per UE to CHF.
5.1.14.4 Void
5.1.15 5G LAN-type Service Communication
5.1.15.1 General
The SMF may support PDU Sessions for a 5G VN group which offers a virtual data network capable of supporting 5G LAN-type service over the 5G system, which specified in the TS 23.501[200].
The SMF embedding the CTF generates 5G VN group communication charging information towards the CHF based on the user plane architecture with the additional following options decribed in the clause 4.4.6 of TS 23.501[200] to support 5G LAN-type service.
– Figure 4.4.6.1-1 depicts the non-roaming user plane architecture to support 5G LAN-type service using local switch.
– Figure 4.4.6.1-2 depicts the non-roaming user plane architecture to support 5G LAN-type service using N19 tunnel.
– Figure 4.1.1 depicts the non-roaming user plane architecture to support 5G LAN-type service using N6 tunnel.
5.1.15.2 Support 5G VN group communication
In order to support the 5G VN group communication, the following principles are used:
– In includes the internal group identifier of 5G VN group, which is used to indicate the 5G VN group and associate charging information for 5G VN group communication.
– The uplink and downlink data volumes of 5G VN group communiucation traffic usage are reported separately.
– The 5G VN group communication using N19 tunnel is measured based on the PDU session charging.
– SMF may report the traffic forwarding way information corresponding to the 5G VN group communication.
5.1.16 Support of Cellular IoT
The 5GS support for Cellular IoT (CIoT) is specified in TS 23.501 [200], this includes EPC interworking and home-routed roaming. In legacy networks Cellular IoT may be referred to as Machine Type Communications (MTC).
During the PDU session establishment (initial charging request) the SMF may provide the following charging information related to 5GS CIoT:
– The indication of Control Plane 5GS CIoT optimization.
– Small data rate control indication.
– The RAT types (NB-IoT or LTE-M).
– The control plane only indication.
5.1.17 Application based charging
If reporting on applications (e.g., edge application) is required it’s recommended to assign each application with its own service id.