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Identifiers play an important role in the 5G system. It is important to understand how identity is handled by public cellular networks. The device would normally connect to the Home network and be authenticated directly. The Authentication process starts with the device requesting access by sending its IMSI/SUPI to the network. 

5G Identifiers 

  • Subscription Permanent Identifier (SUPI) 
  • Subscriber Concealed Identifier (SUCI)
  • 5G Globally Unique Temporary Identity (5G-GUTI)
  • Permanent Equipment Identifier (PEI)
  • Generic Public Subscription Identifier (GPSI) Network Slice Identifiers 
  • AMF Name 
  • Data Network Name (DNN)
  • Internal-Group Identifier 

Subscription Permanent Identifier (SUPI):

5G Subscription Permanent Identifier is a globally unique identifier that is assigned to each subscriber in the 5G system, which is provisioned in the UDM/UDR. A SUPI is usually a string of 15 decimal digits. The first three digits represent the Mobile Country Code (MCC), the next two or three represent the Mobile Network Code (MNC) identifying the network operator. The remainder represents the Mobile Subscriber identification number (MSIN). It represents the individual user of that particular operator. SUPI is equivalent to IMSI which uniquely identifies the ME, which is a string of 15 digits. It is used only within the 3GPP system. The SUPI must contain the address of the home network in order to enable roaming scenarios. For interworking with the EPC, the SUPI allocated to the UE is based on the IMSI number. 

Subscription Permanent Identifier  SUPI

Subscriber Concealed Identifier (SUCI):

It is a privacy-preserving identifier containing the concealed SUPI. The UE generates a SUCI using an ECIES-based protection scheme with the public key of the Home network that was securely provisioned to the USIM during the USIM registration process. It contains the Scheme-output and additional non-concealed information needed for home network routing and protection scheme usage. It contains protection scheme ID, home network public key ID, home network ID e.g MCC and MNC, the SUCI calculation indication, either USIM or ME calculating the SUCI, based on the home operator’s decision indicated by the USIM, the calculation of the SUCI shall be performed either by the USIM or by the ME. 

SUCI Subscriber Concealed Identifier

5G Globally Unique temporary identifier (5G-GUTI)

The 5G GUTI (Globally Unique Temporary Identifier)  is allocated by the AMF (Access and Mobility Management Function). The AMF shall allocate 5G-GUTI to the UE that is common for both 3GPP and non-3GPP access. The AMF may assign a new 5G-GUTI to the UE at any time. The AMF may delay updating the UE with its new 5G-GUTI until the next NAS signaling exchange. The 5G-GUTI comprises a GUAMI (Globally Unique AMF ID) and a 5G-TMSI (Temporary Mobile Subscriber Identity), where GUAMI identifies the assigned AMF and 5G-TMSI identifies the UE uniquely within the AMF. The GUAMI is a concatenation of the PLMN identity and the AMF identifier. 3GPP has specified mapping between the 5G-GUTI and the 4G-GUTI. This mapping is used when a UE moves between technologies. 

5G Globally Unique temporary identifier  GUTI

Permanent Equipment identifier

A PEI is defined for the 3GPP UE accessing the system. The PEI is the means by which the network identifies the user equipment that is capable of accessing a 3GPP network. 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. The UE presents the PEI to the network along with an indication of the PEI formats being used. If the UE supports at least one 3GPP access technology, the UE must be allocated a PEI in the IMEI format. In 3GPP Rel-15, the only format supported for the PEI parameter is an IMEI. 

Generic Public Subscription Identifier (GPSI) Network Slice Identifiers

The GPSI is used as a means of addressing a 3GPP subscription in data networks outside the 3GPP system. These are public identifiers such as MSISDN. The 3GPP system stores within the subscription data the association between the GPSI and the corresponding SUPI. If MSISDN is included in the subscription data, it will be possible that the same MSISDN value is supported in both 5GS and EPS. 

AMF Name

It is used to identify an AMF. It can be configured with one or more GUAMIs. AMF name is a globally unique FQDN (Fully Qualified Domain Name). GUAMI with a distinct AMF pointer value is associated with one AMF only. 

Data Network Name

A DNN is equivalent to an APN. The DNN may be used to: select an SMF and UPF(s) for a PDU session. Select N6 interface(s) for a PDU session. It determines policies to apply to this PDU session. 

Internal Group Identifier

The Subscription data for a UE in UDR (Unified Data Repository) may associate the subscriber with groups. A group is identified by the Internal Group Identifier. UE can belong to a limited number of groups. The group identifiers corresponding to a UE are provided by the UDM. This information is stored in Charging data record.