Radio Network Temporary Identifiers are applicable within the Radio Access Network (RAN).
They are allocated by BS and will be used by both UE and BS.
There are 3 different types of RNTI based on the addressing of UE:
1. C-RNTI: It is used to address an individual UE.
2. INT-RNTI: It is used to address a group of UEs.
3. SI-RNTI: It is used to address all of the UEs. There is a single standard SI-RNTI value that is fixed by 3GPP.
RNTI are used to address the UE to scramble the CRC bits on PDCCH.
PDCCH is used to provide up-link and down-link resource allocation, power control commands, pre-emption indications, slot format changes and system information update.
In this chapter we shall learn about different types of 5G NR RNTI.
Different types of RNTI as per 3GPP 38.321 Table 7.1-2
Following RNTI are used for scheduling at cell level: C-RNTI, CS-RNTI, INT-RNTI, P-RNTI, SI-RNTI and SP-CSI-RNTI.
Following RNTI are used for power and slot format control: SFI-RNTI, TPC-PUCCH-RNTI, TPC-PUSCH-RNTI and TPC-SRS-RNTI
Following are used for random access: RA-RNTI and Temporary C-RNTI
Following RNTI are used for NR connected to 5GC at NG-RAN level:
C-RNTI: It is unique to UE used during RRCConnection and for scheduling.
CS-RNTI: IT is unique to UE and is used for semi-persistent scheduling in the downlink.
P-RNTI: It is used to scramble the CRC bits belonging to DCI format 1_0 when allocating PDSCH resources for the transmission of Paging messages. It is used for identification of paging and system information change notification in the downlink.
SI-RNTI: It is used for all the UE. It is used to scramble the CRC bits belonging to DCI Format 1_0. It is used to identification of broadcast and system information in the downlink.
SP-CSI-RNTI: It is unique to UE and is used for semi-persistent CSI reporting on PUSCH.
SFI-RNTI: It is used to identify slot format.
TPC-PUCCH-RNTI: It is unique to UE and is used for identification to control the power of PUCCH.
TPC-PUSCH-RNTI: It is unique to UE and is used for identification to control the power of PUSCH.
TPC-SRS-RNTI: It is unique to UE and is used for identification to control the power of SRS.
RA-RNTI: It is used for identification of the Random Access Response in the downlink.
Temporary C-RNTI: It is temporary and is used for scheduling during the random access procedure.
I-RNTI: It is used to identify the UE context in RRC_INACTIVE. I-RNTI is used to address the UE with in the RRC signalling messages.