5G Stuff: Identifiers (SUPI, PEI, GUTI...)

As mentioned in 3GPP TS 23501, sec 5.9 and like the earlier 3GPP systems, in 5G system, there are various identifiers at subscriber level and the equipment level.

SUPI          - Subscription Permanent Identifier                 - at Subscriber level
        It is valid only in the 3GPP system, provisioned in the UDM/UDR.
It is based on IMSI (TS 23003) + Network specific identifier (TS 22261). In this way, UE can present its IMSI to the network (EPC) in inter-working scenarios.
For roaming cases, it may take the form of MCC+MNC of IMSI.

PEI             - Permanent Equipment Identifier                   - at UE level
       It may take various forms depends on the Usecases and UE types. UE will indicate the PEI and format of it to the network. If the UE supports atleast one 3GPP technology, it must be allocated a PEI in the IMEI format. In this release, only this IMEI format is supported.          

GUTI         - Globally Unique Temporary Identifier             - at Subscriber level
       AMF is the in-charge to assign (any time) GUTI to an UE and it is common to both 3GPP and non-3GPP access.

     5G GUTI = GUAMI + 5G TMSI

GUAMI identifies the AMF - Globally Unique AMF Identifier 
                 = 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 uniquely identifies the AMF within the AMF Set.

TMSI identifies the UE with in the AMF

Since GUTI is longer, to enable more efficient radio resources (especially in Paging and Service Request), new identifier called 5G-S-TMSI is created.

S-TMSI = AMF SetId + AMF Pointer + 5G-TMSI

SUCI          - Subscription Concealed Identifier                  - at Subscriber level
       It is to preserve the privacy and more details can be found in TS 33501

DNN - Data Network Name - Like APN in earlier access technologies. It is used while creation of PDU session by selecting SMF/UPF/N6 interface and policies determination.

Internal Group Identifier - Depends on the subscription data in UDM, an UE can be grouped which are used in PDU session. In release 15, only non-roaming case is defined though the exact number is defined in Stage 3 specifications.

General Public Subscription Identifier - used inside and outside 3GPP systems. It is needed for addressing a 3GPP subscription in different data networks. 


Single Network Slice Selection Assistance Information S-NSSAI - It identifies the network slice and comprises of SST (Slice/Service Type) and SD 
(Slide Differentiator)

SST - Expected Network slice behavior in terms of features and services
SD - an optional field to differentiate the slice for the same SST

Network Slice Selection Assistance Information NSSAI - It is a collection of S-NSSAIs and up to 8 in allowed and requested NSSAIs sent in the signaling messages between the UE and the network.