Network-Controlled Repeater Type 1-H

Description

NCR type 1-H is a specific class of network-controlled repeater (NCR) defined by 3GPP for operation in Frequency Range 1 (FR1, typically 410 MHz to 7.125 GHz). An NCR is an advanced repeater that receives and amplifies signals between a gNB and user equipment (UE), but unlike traditional repeaters, its forwarding behavior is controlled by the network via a dedicated control link. Type 1-H includes two key logical entities: the NCR Mobile Termination (NCR-MT), which handles control-plane communication with the network, and the NCR Forwarding (NCR-Fwd), which performs the actual signal amplification and forwarding. Both entities operate at FR1, meaning the control link and the forwarded signals use FR1 frequencies.

In terms of architecture, the NCR-MT acts as a UE-like entity that maintains a control connection to the gNB (or a donor node) using the NR Uu interface. Through this link, the network can configure parameters such as beams, gain, and on/off states for the NCR-Fwd. The NCR-Fwd uses analog or hybrid beamforming to amplify and forward signals in specific spatial directions. Because the NCR operates at FR1, it can support both conducted and over-the-air (OTA) test methodologies. Conducted requirements are defined at individual Test Access Board (TAB) connectors, which are standardized interfaces on the NCR equipment for testing purposes. OTA requirements are defined at the Radiated Interface Boundary (RIB), which is an imaginary surface around the equipment where radiated signals are evaluated. This dual requirement set allows manufacturers and operators to verify performance using either conducted or radiated test setups.

The key distinction of type 1-H from other NCR types is its support for both NCR-MT and NCR-Fwd at FR1 and its requirement set that includes both conducted and OTA tests. This makes it suitable for deployments where antenna connectors are available (conducted testing) but also where OTA testing is needed, for example in compact integrated designs. The NCR type 1-H is specifically designed to enhance network coverage and capacity in FR1 bands without the need for costly backhaul or fiber, by simply amplifying and forwarding signals under network control.

In the network, NCR type 1-H can be deployed in various scenarios: indoor hotspots, urban canyons, or rural areas where signal penetration is poor. It helps fill coverage holes, extend cell edge throughput, and improve user experience. Because it is network-controlled, it can adapt to changing traffic and interference conditions, unlike traditional repeaters that operate autonomously. The control link ensures that the NCR does not amplify noise or create harmful interference, as the network can adjust its gain and beam direction. The NCR-MT also allows the NCR to be integrated into the network's management and self-optimization framework.

From a standardization perspective, NCR type 1-H was introduced in Release 19 and is specified in 3GPP TS 38.106 (NCR overall description) and TS 38.114 (NCR requirements). The conducted requirements at TAB connectors ensure that the NCR can be tested using standard lab equipment, while OTA requirements at RIB enable evaluation of the radiated performance, which is crucial for active antenna systems. This dual approach provides flexibility in testing and ensures that both conducted and radiated performance are validated, leading to more reliable deployments. In Release 19 and Release 20, the definition of type 1-H was clarified in Rel-20 to indicate that the NCR includes either NCR-MT or NCR-Fwd operating at FR1, meaning not necessarily both simultaneously, which allows for scenarios where only one entity is active.

Purpose & Motivation

NCR type 1-H exists to address coverage and capacity challenges in FR1 bands, where signal propagation is limited by obstacles and distance. Traditional repeaters are simple amplifiers that operate without network control, often causing interference and noise enhancement. NCRs, by contrast, are controlled by the network, allowing dynamic adjustment of gain, beams, and activation to optimize performance while minimizing interference. Type 1-H specifically targets FR1 deployments where both conducted and OTA testing are feasible, providing a flexible solution for network operators to extend coverage in sub-6 GHz bands. The motivation for introducing NCR in Release 19 was to enable cost-effective coverage extension without the need for additional backhaul, especially in areas where deploying new base stations is impractical. Type 1-H's dual test requirement set ensures that manufacturers can design equipment that meets both conducted and radiated performance criteria, facilitating global harmonization and interoperability.