Description
The Interruption RNTI (INT-RNTI) is a specific type of Radio Network Temporary Identifier allocated by the gNB to a UE in 5G New Radio (NR). It is used to manage and signal uplink transmission interruptions, which are periods when the UE must temporarily halt its uplink transmissions. The INT-RNTI is included in Downlink Control Information (DCI) formats, allowing the gNB to efficiently command multiple UEs to interrupt uplink transmissions simultaneously or in a coordinated manner. This identifier is crucial for scenarios requiring silent periods, such as when performing Radio Resource Management (RRM) measurements, sensing for spectrum sharing, or mitigating cross-link interference in Time Division Duplex (TDD) systems.
Operationally, when the gNB needs to create an interruption window, it sends a DCI scrambled with the INT-RNTI. UEs monitor the PDCCH for this RNTI and, upon detection, interpret the DCI to determine the timing and duration of the required interruption. The DCI may specify parameters like the start symbol, length, and affected bandwidth part. During the interruption, the UE ceases uplink transmissions on the indicated resources, allowing the network or other UEs to perform measurements without interference. The INT-RNTI mechanism supports dynamic and flexible scheduling of interruptions, adapting to real-time network conditions.
Key components involve the RNTI allocation procedure, DCI format design (e.g., DCI format 2_0 with slot format indication, or other formats enhanced for interruption signaling), and UE behavior specifications. INT-RNTI plays a vital role in enhancing spectrum utilization, enabling efficient coexistence mechanisms in shared and unlicensed bands (NR-U), and improving mobility performance through accurate neighbor cell measurements. It is integral to 5G's advanced features like dynamic spectrum sharing and ultra-reliable low-latency communications (URLLC) where precise timing control is essential.
Purpose & Motivation
INT-RNTI was introduced in 5G NR to address the need for controlled uplink interruptions in dynamic spectrum environments. In earlier releases, interruption mechanisms were less standardized or relied on semi-static configurations, which lacked flexibility. With the advent of 5G and operations in shared spectrum (e.g., 3.5 GHz CBRS, unlicensed 5 GHz/6 GHz), there is a requirement for agile and network-coordinated silent periods to facilitate sensing, interference avoidance, and fair coexistence with other systems like Wi-Fi or incumbent users.
The primary problem solved is the efficient management of uplink transmissions to prevent them from obstructing critical network functions. For instance, in TDD networks, uplink transmissions from one cell can interfere with downlink receptions in adjacent cells. INT-RNTI enables the gNB to quickly mute specific UEs, mitigating cross-link interference. Additionally, it supports enhanced RRM measurements for mobility, as uninterrupted uplink signals can mask neighbor cell reference signals. By providing a standardized, RNTI-based signaling method, 3GPP ensures reliable and low-latency control of interruptions, which is essential for meeting 5G performance targets in diverse deployment scenarios.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (12 CRs across 4 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the INT-RNTI (Interruption RNTI) was newly introduced as a function for downlink scheduling to support pre-emption of ongoing PDSCH transmissions. Specifically, the gNB can configure UEs to monitor interrupted transmission indications using INT-RNTI on a PDCCH, allowing a UE to assume that no useful information for it was carried in the indicated pre-empted resource elements. This mechanism enables latency-critical transmissions to other UEs by dynamically indicating which scheduled resources have been interrupted.
In Release 16, the INT-RNTI function was enhanced to support operation in shared spectrum, specifically for NR-U (NR in Unlicensed spectrum). The specification clarified that a gNB can configure UEs to monitor interrupted transmission indications using the INT-RNTI on a PDCCH, allowing the UE to assume no useful information was sent in the indicated resources. This mechanism supports pre-emption of an ongoing PDSCH to prioritize latency-critical transmissions to another UE in the unlicensed band.
- Introduction of NR-U in 38.321 TS 38.321CR0694
- Correction of CAPC for NR-U TS 38.300CR0294
- Correction on prioritization between DCP and RAR to C-RNTI for CFRA BFR TS 38.300CR0295
- Correction on prioritization between DCP and RAR to C-RNTI for CFRA BFR – Option 2 TS 38.321CR0794
- Correction on resource overlapping with grants addressed to TC-RNTI TS 38.321CR0927
- Correction for Uplink Grant Received in RAR and Addressed to Temporary C-RNTI TS 38.321CR1026
+ 2 more changes
In Release 17, the INT-RNTI function was enhanced to allow the gNB to configure UEs to monitor interrupted transmission indications specifically on a PDCCH. This enables the network to indicate that a pre-empted PDSCH resource contains no useful data for the scheduled UE, improving the efficiency of latency-critical transmissions. The function provides a clear mechanism for handling resource conflicts in the downlink.
- Introduction of PEI-RNTI TS 38.321CR1262
In Release 18, the INT-RNTI function was enhanced to support operation in shared spectrum, specifically for NR-U (New Radio in Unlicensed spectrum). The grounding context clarifies that the gNB configures UEs to monitor interrupted transmission indications using INT-RNTI on a PDCCH, allowing the gNB to pre-empt an ongoing PDSCH transmission for a latency-critical transmission to another UE.
- Stage 2 correction for NR-U TS 38.300CR0825
Explore further
Broader topics and technologies where INT-RNTI plays a role.
Defining Specifications
3GPP specifications that define or reference INT-RNTI, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 38.300 vj00 | NG-RAN Overall Description | Rel-19 |
| TS 38.321 vj00 | NR MAC Protocol Specification | Rel-19 |