Section: 5.5.3.8 Charging Principles for roaming architecture for voice over IMS with home routed traffic
Content: The roaming architecture for voice over IMS with home routed traffic is described in the TS 23.228[ IP Multimedia Subsystem (IMS); Stage 2 ]  [209]. The breakout point for both the IMS signalling and media traffic is in the home network for a roaming UE, i.e. for 3GPP systems, the P-GW/GGSN/SMF-UPF for a roaming UE is in the HPLMN of the UE. Based on GSMA BA.27 [500], the VPLMN will not have awareness of the services being used over the IMS APN and cannot support service-aware wholesale charging. Data roaming charges will apply for all traffic traversing S8 or Gp interface per the existing data roaming agreement. The HPLMN operator will be responsible for all interworking connectivity and call termination fees associated with call or service termination. Specifically, the serving PLMN identifier of the UE is needed for the home network. Details are described in the TS 32.260[ Telecommunication management;Charging management;IP Multimedia Subsystem (IMS) charging ]  [20].