RNTI Values and Usage in 5G NR
RNTI Values and Usage in 5G NR
In 5G NR, RNTI (Radio Network Temporary Identifier) values are crucial for identifying different types of communication in the network. They distinguish between control and data transmissions, enabling efficient resource management. Each RNTI has a specific function, such as signaling (e.g., RA-RNTI for random access), data transmission (e.g., C-RNTI for UE-specific communication), or special cases like sidelink communications (e.g., SL-RNTI).
RNTIs are represented in hexadecimal format and are dynamically allocated based on network requirements, ensuring flexibility and scalability. They are fundamental to 5G network operations, supporting diverse use cases from high-speed mobile broadband to massive IoT and ultra-reliable low-latency communication.
Key Concepts
- RNTI Function: Identifies different types of communication contexts within a 5G NR network.
- RNTI Types: RA-RNTI (random access), C-RNTI (UE-specific communication), SL-RNTI (sidelink communications), etc.
- RNTI Allocation: Dynamically allocated in hexadecimal format to ensure flexibility and scalability.
RNTI Value Ranges
| Value (Hexadecimal) | RNTI |
|---|---|
| 0000 | N/A |
| 0001–FFF2 | RA-RNTI, MSGB-RNTI, Temporary C-RNTI, C-RNTI, CI-RNTI, MCS-C-RNTI, CS-RNTI, TPC-PUCCH-RNTI, TPC-PUSCH-RNTI, TPC-SRS-RNTI, INT-RNTI, SFI-RNTI, SP-CSI-RNTI, PS-RNTI, SL-RNTI, SL-CS-RNTI, SL Semi-Persistent Scheduling V-RNTI, AI-RNTI, G-RNTI, G-CS-RNTI, and CG-SDT-CS-RNTI |
| FFF3–FFFB | Reserved |
| FFFC | PEI-RNTI |
| FFFD | MCCH-RNTI |
| FFFE | P-RNTI |
| FFFF | SI-RNTI |
RNTI Usage and Transport/Logical Channels
| RNTI | Usage | Transport Channel | Logical Channel |
|---|---|---|---|
| P-RNTI | Paging and System Information change notification | PCH | PCCH |
| SI-RNTI | Broadcast of System Information | DL-SCH | BCCH |
| RA-RNTI | Random Access Response | DL-SCH | N/A |
| MSGB-RNTI | Random Access Response for 2-step RA type | DL-SCH | CCCH, DCCH, DTCH |
| Temporary C-RNTI | Contention Resolution (when no valid C-RNTI is available) | DL-SCH | CCCH, DCCH, DTCH |
| Temporary C-RNTI | Msg3 transmission | UL-SCH | CCCH, DCCH, DTCH |
| C-RNTI, MCS-C-RNTI | Dynamically scheduled unicast transmission | UL-SCH | DCCH, DTCH |
| C-RNTI | Dynamically scheduled unicast transmission | DL-SCH | CCCH, DCCH, DTCH |
| MCS-C-RNTI | Dynamically scheduled unicast transmission | DL-SCH | DCCH, DTCH |
| C-RNTI | Triggering of PDCCH ordered random access | N/A | N/A |
| C-RNTI | Dynamically scheduled PTP retransmission for initial PTM transmission for multicast MBS | DL-SCH | MTCH |
| CG-SDT-CS-RNTI | Dynamically scheduled unicast transmission (retransmission) | UL-SCH | CCCH, DCCH, DTCH |
| CS-RNTI | Configured scheduled unicast transmission (activation, reactivation and retransmission) | DL-SCH, UL-SCH | DCCH, DTCH |
| CS-RNTI | Configured scheduled unicast transmission (deactivation) | N/A | N/A |
| CS-RNTI | Configured scheduled unicast transmission (PTP retransmission for initial PTM transmission) | DL-SCH | MTCH |
| CS-RNTI | Configured scheduled unicast transmission (MBS SPS deactivation) | N/A | N/A |
| G-CS-RNTI | Configured scheduled multicast transmission (activation, reactivation and retransmission) | DL-SCH | MTCH |
| G-CS-RNTI | Configured scheduled multicast transmission (deactivation) | N/A | N/A |
| TPC-PUCCH-RNTI | PUCCH power control | N/A | N/A |
| TPC-PUSCH-RNTI | PUSCH power control | N/A | N/A |
| TPC-SRS-RNTI | SRS trigger and power control | N/A | N/A |
| INT-RNTI | Indication pre-emption in DL | N/A | N/A |
| SFI-RNTI | Slot Format Indication on the given cell | N/A | N/A |
| SP-CSI-RNTI | Activation of Semi-persistent CSI reporting on PUSCH | N/A | N/A |
| CI-RNTI | Cancellation indication in UL | N/A | N/A |
| PS-RNTI | DCP to indicate whether to start drx-onDurationTimer for associated DRX cycle | N/A | N/A |
| SL-RNTI | Dynamically scheduled sidelink transmission | SL-SCH | SCCH, STCH |
| SL-CS-RNTI | Configured scheduled sidelink transmission (activation, reactivation and retransmission) | SL-SCH | SCCH, STCH |
| SL-CS-RNTI | Configured scheduled sidelink transmission (deactivation) | N/A | N/A |
| SL Semi-Persistent Scheduling V-RNTI (NOTE 2) | Semi-Persistently scheduled sidelink transmission for V2X sidelink communication (activation, reactivation and retransmission) | SL-SCH | STCH |
| SL Semi-Persistent Scheduling V-RNTI (NOTE 2) | Semi-Persistently scheduled sidelink transmission for V2X sidelink communication (deactivation) | N/A | N/A |
| AI-RNTI | Availability indication on the given cell | N/A | N/A |
| G-RNTI | Dynamically scheduled MBS PTM transmission | DL-SCH | MTCH |
| MCCH-RNTI | Dynamically scheduled MCCH signalling and MCCH change notification | DL-SCH | MCCH |
| PEI-RNTI | Paging Early Indication | N/A | N/A |
"Mapping of Logical channels to Transport channels in 5G NR MAC layer."
NOTE 1: The usage of MCS-C-RNTI is equivalent to that of C-RNTI in MAC procedures (except for the C-RNTI MAC CE).
NOTE 2: The MAC entity uses SL Semi-Persistent Scheduling V-RNTI to control semi-persistently scheduled sidelink transmission on SL-SCH for V2X sidelink communication as specified in clause 5.14.1.1 of TS 36.321.
NOTE 3: The usage of CG-SDT-CS-RNTI is equivalent to that of CS-RNTI when there is an CG-SDT procedure ongoing.
FAQ: Understanding RNTI
What is RNTI in 5G NR?
RNTI stands for Radio Network Temporary Identifier. It is used to uniquely identify User Equipment (UE) or specific communication contexts in the 5G network.
Why are RNTI values important?
RNTI values are crucial for managing resources, ensuring efficient signaling, and maintaining communication sessions between the network and devices.
What are some common types of RNTI?
Common types include:
- RA-RNTI: Used during random access procedures.
- C-RNTI: Identifies a specific UE for dedicated communication.
- SL-RNTI: Used for sidelink communication in device-to-device (D2D) scenarios.
Are RNTI values static?
No, RNTI values are dynamic. They are dynamically assigned and released based on network conditions and the state of the communication session.
How are RNTI values represented?
RNTI values are typically represented in hexadecimal format (0000 to FFFF), with each range designated for specific purposes, such as signaling or data transmission.
Can multiple devices share the same RNTI?
No, generally RNTI values (like C-RNTI) are unique within a specific context (cell) to avoid conflicts and ensure reliable communication. However, some RNTIs like SI-RNTI or P-RNTI are common to multiple UEs.
References
- 3GPP TS 38.321: NR; Medium Access Control (MAC) protocol specification
Further Reading
WirelessBrew Team
Technical expert at WirelessBrew, specializing in 5G NR, LTE, and wireless system optimization. Committed to providing accurate, 3GPP-compliant engineering tools.
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