A PEI is defined for the 3GPP UE accessing the 5G System.
The PEI can assume different formats for different UE types and use cases. The UE shall present the PEI to the network together with an indication of the PEI format being used.
If the UE supports at least one 3GPP access technology, the UE must be allocated a PEI in the IMEI format.
In the scope of this release, the only format supported for the PEI parameter is an IMEI.
The public service identity shall take the form of either a SIP URI or a Tel URI. A public service identity identifies a service, or a specific resource created for a service on an
application server. The domain part is pre-defined by the IMS operators and the IMS system provides the flexibility to
dynamically create the user part of the PSIs.
The PSIs are stored in the HSS either as a distinct PSI or as a wildcarded PSI.