The objective of this Technical Report is to investigate scenarios for co-existence of subscription data pertaining to legacy system (EPS) with data pertaining to the 5G system, when the HSS+UDM defined in Rel-15 is separated and both UDM and HSS are independent, and will propose solutions to support this deployment where necessary.
study diverse scenarios related to the storage of subscription data including, but not limited to, those of common repository for subscription data from EPS and 5GS, as well as separate repositories for EPS and 5GS subscription data,
investigate the relevant procedures in TS 23.502 (for e.g. authentication, mobility, handover and procedures for IMS and SMS handling in interworking between 5G system and EPS),
determine if there is a need for interaction between the consumers of EPS and 5GS data, in the different interworking cases and deployment scenarios.
Existing procedures in TS 23.502 shall not be impacted.
Provisioning aspects are outside this study.
Direct interactions between the EPS UDR and the 5GS UDR are out of the scope of this TR (i.e. it is assumed that there is no direct interaction between these two repositories).