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5G NR Identifiers: UE and Network IDs Explained

5g 5g nr identifiers network user equipment

This article explains the different identifiers used in 5G New Radio (NR) for both User Equipment (UE) and the network infrastructure. These identifiers are crucial for managing connections, mobility, and overall network operation.

5G UE Identifiers: C-RNTI, Temporary C-RNTI

The following table describes the various identifiers used for 5G UEs:

Table 1: 5G UE Identifiers

5G UE IdentifiersDescription
C-RNTIUsed for RRC connection establishment and scheduling. In dual connection scenarios, two C-RNTIs are allocated to the UE independently for Master Cell Group (MCG) and Slave Cell Group (SCG) functionalities.
Temporary C-RNTI• Used during the random access procedure.
• Also functions as a random value for contention resolution by the UE in specific transient states.
I-RNTIUsed to identify the UE Context for the RRC_INACTIVE state. It is used at the NG-RAN level when NR is connected to the 5G Core (5GC).

5G Network Identifiers: AMF, NCGI, gNB ID, Global gNB ID, TAI

The subsequent table details the identifiers employed within the 5G network:

Table 2: 5G Network Identifiers

5G Network IdentifiersDescription
AMFUsed to uniquely identify the Access and Mobility Management Function (AMF).
NCGI• Identifies NR cells on a global scale.
• Constructed from two key components: PLMN (Public Land Mobile Network) and NCI (NR Cell Identity).
gNB ID• Identifies individual gNBs (5G base stations) within a specific PLMN.
• The NCI (NR Cell Identity) of cells contains the gNB ID field.
Global gNB ID• Globally identifies gNBs.
• Constructed from the PLMN and the gNB ID.
• Uses the same MCC (Mobile Country Code) and MNC (Mobile Network Code) as used in the NCGI.
TAI• Short for Tracking Area Identity.
• Used to identify tracking areas within the network.
• Constructed from the PLMN of the tracking area and the TAC (Tracking Area Code).

References:

(1.) 3GPP TS 38.300 (2.) TS V5G.300