4.2 High level common architecture

32.2403GPPCharging architecture and principlesCharging managementRelease 18Telecommunication managementTS

4.2.1 General

The architectural differences between the domains (e.g. PS), services (e.g. MMS) and subsystems (e.g. the IMS) affect the way in which the charging functions are embedded within the different domains, services and subsystems. However, the functional requirements for charging are always the same across all domains, services and subsystems. This clause describes a common approach for the definition of the logical charging functions, which provides a ubiquitous logical charging architecture for all 3GPP network domains, subsystems and services that are relevant for charging standardisation.

It should be noted that this common charging architecture provides only a common logical view and the actual domain / service / subsystem specific charging architecture depends on the domain / service / subsystem in question. The physical mapping of the common logical architecture onto each domain, subsystem or service is described in the respective middle tier TS, i.e. the TS 32.25x, TS 32.26xand TS 32.27x number ranges.

Figure 4.2.1.1 provides an overview of the logical ubiquitous charging architecture and the information flows for offline and online charging, in both referent points and service based interface variants, respectively further detailed in clause 4.2.2 and clause 4.2.3.

The common architecture for Network Slice Charging is provided in clause 4.2.4

The common charging functions are detailed further for the reference points variant, in clauses 4.3.1 for offline charging, and clause 4.3.2 for online charging, and for the service based interface variant in clause 4.3.3 for converged online and offline charging. The reference points are further specified in clause 4.4. The service based interface is further specified in clause 4.2.3.

Figure 4.2.1.1: Logical ubiquitous charging architecture and information flows

4.2.2 Common architecture – reference points

Figure 4.2.2.1 provides an overview of the logical ubiquitous charging architecture and the information flows for offline and online charging in reference points variant for non-5G systems.

NOTE: this was formerly figure 4.2.1.

Figure 4.2.2.1: Logical ubiquitous charging architecture and information flows for non-5G systems– reference points

NOTE 0: The Service-NE are defined in the 3GPP specification range of TS 32.27x.

Figure 4.2.2.1 includes all network elements / systems (top to bottom: CS-NE all the way through to the PCEF) for which charging is defined within 3GPP standards. The arrows indicate logical information flows on the Rf, Ga, Bx, ISC, Ro, CAP, Gy and Gyn reference points. No inference should be drawn from the figure 4.2.2.1 with respect to the physical implementation of interfaces and charging functions.

NOTE 1: On the PCEF embedded in PGW, TS 23.203 [208] specifies the Gy reference point for online flow based bearer charging and the Gz reference point for offline flow based bearer charging. However, from the charging architecture perspective, Gy is functionally equivalent to the Ro reference point. Gz is functionally equivalent to the Ga reference point for the Legacy PS domain, and to one of Ga or Rf reference points for the Evolved PS domain. Therefore, throughout the present document, Ga or Rf are used for offline, and Ro for online are also used in conjunction with PCEF charging. This simplification ensures a consistent architectural view, as specified below, for all PCEF related online and offline charging architectural aspects.

Refer to clause 5.3.1.2 for a description of flow based bearer charging.

NOTE 2: Void.

NOTE 3: Only SMS Charging is defined for MME, as specified in TS 23.272 [213].

NOTE 4: As specified in TS 23.203 [208], the TDF uses the Gyn reference point for online application based charging and the Gzn reference point for offline application based charging. However, from the charging architecture perspective Gyn is functionally equivalent to the Ro reference point and Gzn is functionally equivalent to one of Ga or Rf reference points in the PS domain. Therefore, throughout the present document, Ga or Rf for offline, and Ro for online are also used in conjunction with TDF charging. This simplification ensures a consistent architectural view, as specified below, for all TDF related online and offline charging architectural aspects.

The logical ubiquitous charging architecture and the information flows for offline and online charging applied to the convergent scenario (i.e. both the Fixed Broadband Access network and Evolved Packet Core (EPC) owned by a single operator) with PCEF located in Fixed Broadband Access is defined in annex C, clause C.4.2.

To implement roaming unbundling for EU roaming regulation III, an architectural solution known as the Single IMSI architecture has been defined in EU Roaming regulation III; Structural Solutions; High Level Technical Specifications [298]. This architecture is based on the introduction of specific Service-NE (known as a Proxy Function) which uses the Ro reference point for online charging. The details of this architecture are defined in annex B.

4.2.3 Common architecture – service based interface

The following figures provide an overview of the logical ubiquitous charging architecture and the information flows for converged offline and online charging in service based interface variant for 5G systems and Edge Computing enabling sub-systems.

Figure 4.2.3.1 provides the overview in service based representation:

Figure 4.2.3.1: Logical ubiquitous charging architecture and information flows for 5G systems – service based representation

Figure 4.2.3.2 provides the overview in reference point representation:

Figure 4.2.3.2: Logical ubiquitous charging architecture and information flows for 5G systems – reference point representation

The reference points are defined in clause 4.4.3.

For the sake of simplicity, the SMF+PGW-C is not explicitly added in Figure 4.2.3.1 and Figure 4.2.3.2, and is represented by the SMF.The SMF+PGW-C uses Nchf for 5GS and EPC interworking as well as when enhanced to support GERAN/UTRAN.

The Nchf_SpendingLimitControl service exposed by CHF and consumed by the PCF is specified in TS 23.502 [214].

4.2.4 Common architecture – management domain

Figure 4.2.4.1 provides an overview of the logical ubiquitous charging architecture for the management domain with MDAS.

Figure 4.2.4.2 provides an overview of the logical ubiquitous charging architecture for the management (MDAS) and control domain (NWDAF).

Figure 4.2.4.3 provides an overview of the logical ubiquitous charging architecture for the management with other management.

Figure 4.2.4.1: Logical ubiquitous charging architecture for management domain

Figure 4.2.4.2: Logical ubiquitous charging architecture for management domain (MDAS) and control domain (NWDAF)

Figure 4.2.4.3: Logical ubiquitous charging architecture for other management layers

This common charging architecture provides only a common logical view. The above figures illustrate three options on how CEF can consume those described. The CEF can either consume management services or services exposed by Network functions (e.g. NWDAF), and is also a consumer of Nchf, this is illustrated in figure 4.2.4.1 which can be adapted to requirements of the Service Provider, an additional scenario (depicted in 4.2.4.3) would allow the consumption of other management services (e.g. provisioning service, notification service)

The Network Data Analytics Function (NWDAF) is specified in TS 23.501 [215].

The MnS producer, MnS consumer and MDAS are defined in TS 28.533 [216].

The Charging Enablement Function (CEF) is defined in clause 4.3.3.3