Interruption RNTI

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.

Key Features

• Dynamic signaling of uplink interruption commands via DCI
• Support for group-common interruptions targeting multiple UEs
• Configurable interruption duration and resource allocation
• Enhancement for NR-U coexistence and spectrum sharing
• Integration with TDD cross-link interference management
• Low-latency control for URLLC and measurement gaps

Evolution Across Releases

Defining Specifications