Section: 4.2.2 Common architecture – reference points
Content: 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 32.27[ None ] x. 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[ Policy and charging control architecture ]  [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[ Circuit Switched (CS) fallback in Evolved Packet System (EPS); Stage 2 ]  [213]. NOTE 4: As specified in TS 23.203[ Policy and charging control architecture ]  [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.