(Based on 3GPP Specification in Release 15 and 16)
Each subscriber in the 5G System is allocated one 5G Subscription Permanent Identifier (SUPI) for use within the 3GPP system. The 5G System supports identification of subscriptions independently of identification of the user equipment. Each UE accessing the 5G System shall be assigned a Permanent Equipment Identifier (PEI).
The 5G System supports allocation of a temporary identifier (5G-GUTI) in order to support user confidentiality protection.
Subscription Permanent Identifier
A globally unique 5G Subscription Permanent Identifier (SUPI) is allocated to each subscriber in the 5G System and provisioned in the UDM/UDR. The SUPI is used only inside 3GPP system
The SUPI may contain:
– an IMSI
– a network-specific identifier, used for private networks as defined in TS 22.261 .
– a GLI and an operator identifier of the 5GC operator, used for supporting FN-BRGs
– a GCI and an operator identifier of the 5GC operator, used for supporting FN-CRGs and 5G-CRG
A SUPI containing a network-specific identifier shall take the form of a Network Access Identifier (NAI)
When UE needs to indicate its SUPI to the network (e.g. as part of the Registration procedure), the UE provides the SUPI in concealed form
In order to enable roaming scenarios, the SUPI shall contain the address of the home network (e.g. the MCC and MNC in the case of an IMSI based SUPI).
For interworking with the EPC, the SUPI allocated to the 3GPP UE shall always be based on an IMSI to enable the UE to present an IMSI to the EPC.
Subscription Concealed Identifier
The Subscription Concealed Identifier (SUCI) is a privacy preserving identifier containing the concealed SUPI.
Permanent Equipment Identifier
A Permanent Equipment Identifier (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 (i.e. NG-RAN, E-UTRAN, UTRAN or GERAN), the UE must be allocated a PEI in the IMEI or IMEISV format.
PEI may be one of the following:
– for UEs that support at least one 3GPP access technology, an IMEI or IMEISV
– PEI used in the case of W-5GAN access
– for UEs not supporting any 3GPP access technologies, the IEEE Extended Unique Identifier EUI-64  of the access technology the UE uses to connect to the 5GC.
5G Globally Unique Temporary Identifier
The AMF allocates a 5G Globally Unique Temporary Identifier (5G-GUTI) to the UE that is common to both 3GPP and non-3GPP access. It shall be possible to use the same 5G-GUTI for accessing 3GPP access and non-3GPP access security context within the AMF for the given UE. An AMF may re-assign a new 5G-GUTI to the UE at any time. The AMF provides a new 5G-GUTI to the UE under the specific conditions When the UE is in CM-IDLE, the AMF may delay providing the UE with a new 5G-GUTI until the next NAS transaction.
The 5G-GUTI shall be structured as:
<5G-GUTI>: = <GUAMI> <5G-TMSI>
where GUAMI identifies one or more AMF(s).
When the GUAMI identifies only one AMF, the 5G-TMSI identifies the UE uniquely within the AMF. However, when AMF assigns a 5G-GUTI to the UE with a GUAMI value used by more than one AMF, the AMF shall ensure that the 5G-TMSI value used within the assigned 5G-GUTI is not already in use by the other AMF(s) sharing that GUAMI value.
The Globally Unique AMF ID (GUAMI) shall be structured as:
<GUAMI>: = <MCC> <MNC> <AMF Region ID> <AMF Set ID> <AMF Pointer>
where AMF Region ID identifies the region, AMF Set ID uniquely identifies the AMF Set within the AMF Region and AMF Pointer identifies one or more AMFs within the AMF Set.
The 5G-S-TMSI is the shortened form of the GUTI to enable more efficient radio signalling procedures (e.g. during Paging and Service Request) and is defined as:
<5G-S-TMSI> := <AMF Set ID> <AMF Pointer> <5G-TMSI>
The NG-RAN uses the 10 Least Significant Bits of the 5G-TMSI in the determination of the time at which different UEs are paged. Hence, the AMF shall ensure that the 10 Least Significant Bits of the 5G-TMSI are evenly distributed.
An AMF is identified by an AMF Name. AMF Name is a globally unique FQDN. An AMF can be configured with one or more GUAMIs. At a given time, GUAMI with distinct AMF Pointer value is associated to one AMF name only.
Data Network Name (DNN)
A DNN is equivalent to an APN. Both identifiers have an equivalent meaning and carry the same information.
The DNN may be used e.g. to:
– Select a SMF and UPF(s) for a PDU Session.
– Select N6 interface(s) for a PDU Session.
– Determine policies to apply to this PDU Session.
The subscription data for an UE in UDR may associate the subscriber with groups. A group is identified by an Internal-Group Identifier.
The Internal-Group Identifier(s) corresponding to an UE are provided by the UDM to the SMF as part Session Management Subscription data and (when PCC applies to a PDU Session) by the SMF to the PCF. The SMF may use this information to apply local policies and to store this information in CDR. The PCF may use this information to enforce AF requests
The Internal-Group Identifier(s) corresponding to an UE are provided by the UDM to the AMF as part of Access and Mobility Subscription data. The AMF may use this information to apply local policies
Generic Public Subscription Identifier
Generic Public Subscription Identifier (GPSI) is needed for addressing a 3GPP subscription in different data networks outside of the 3GPP system. The 3GPP system stores within the subscription data the association between the GPSI and the corresponding SUPI.
GPSIs are public identifiers used both inside and outside of the 3GPP system.
The GPSI is either an MSISDN or an External Identifier. If MSISDN is included in the subscription data, it shall be possible that the same MSISDN value is supported in both 5GS and EPS.
AMF UE NGAP ID
An AMF UE NGAP ID is an identifier used to identify the UE in AMF on N2 reference point. AMF allocates the AMF UE NGAP ID and send it to the 5G-AN. For the following N2 signalling interaction sent from 5G-AN to AMF, AMF UE NGAP ID is used to identify the UE at the AMF. AMF UE NGAP ID is unique per AMF set. AMF UE NGAP ID may be updated without AMF change, or with AMF change.
UE Radio Capability ID
The UE Radio Capability ID is is used to uniquely identify a set of UE radio capabilities (i.e. UE Radio Capability information). The UE Radio Capability ID is assigned either by the serving PLMN or by the UE manufacturer, as follows:
– UE mmanufacturer-assigned: The UE Radio Capability ID may be assigned by the UE manufacturer in which case it includes a UE manufacturer identification (i.e. a Vendor ID). In this case, the UE Radio Capability ID uniquely identifies a set of UE radio capabilities for a UE by this manufacturer in any PLMN.
– PLMN-assigned: If a UE manufacturer-assigned UE Radio Capability ID is not used by the UE or the serving network, or it is not recognised by the serving PLMN UCMF, the UCMF may allocate UE Radio Capability IDs for the UE corresponding to each different set of UE radio capabilities the PLMN may receive from the UE at different times. In this case, the UE Radio Capability IDs the UE receives are applicable to the serving PLMN and uniquely identify the corresponding sets of UE radio capabilities in this PLMN. The PLMN assigned UE Radio Capability ID includes a Version ID in its format. The value of the Version ID is the one configured in the UCMF, at time the UE Radio Capability ID value is assigned. The Version ID value makes it possible to detect whether a UE Radio Capability ID is current or outdated.
The type of UE Radio Capability ID (UE manufacturer-assigned or PLMN-assigned) is distinguished when a UE Radio Capability ID is signalled.