GSMA has identified a new roaming model for VoLTE called "S8 Home Routed (S8HR)" whereby the PGW, PCRF
and P-CSCF are located in the HPLMN also when the UE is roaming in a VPLMN. S8HR roaming architecture aims to
provide IMS services to UEs roaming in VPLMN with the UE to network IMS interface (Gm) between the UE and the
HPLMN only and not requiring any IMS network to network interface (NNI) between the VPLMN and HPLMN.
The present document studies and evaluates the architecture enhancements required to support S8HR for VoLTE. The
architecture enhancements should also be applicable to other IMS services.
The study will cover at a minimum the following topics:
Support of Emergency calls to meet regulatory requirement
Impacts on SRVCC for the S8HR roaming scenarios required by GSMA.
Coexistence of LBO and S8HR roaming architectures
Providing VPLMN Identity to IMS entities in HPLMN
Handling of geo-local number