NTT DoCoMo targets indoor mmWave with new multisector antenna

Japanese companies demonstrate new antenna for indoor mmWave.

A consortium of Japanese companies has demonstrated a new antenna operating in mmWave bands indoors. The antenna used a multisector design in the 28GHz band, and was designed to be small in size.

Yokohama National University, NTT DOCOMO, NIHON DENGYO KOSAKU and Fujitsu said that the antenna”incorporates circuitry just 1/10th the size of a conventional indoor base station”. That means it is “extra small for easy installation, minimises energy consumption and achieves highly efficient signal propagation, all of which will contribute to the realization of high-quality connectivity indoors.”

The demonstration connected a conventional 5G base station CU to the antenna, and, according to the participating companies, “confirmed that a single multisector antenna can receive radio waves in all directions using radio beam control.”  The emission of radio waves from the multi-sector antenna in all directions
and switching by radio beam control were confirmed at a large anechoic chamber in the NTT DOCOMO R&D Center on Friday, January 27.

The demo used 400MHz bandwidth within the 28GHz band, with 2 MIMO layers and 12 beam settings. Yokohama National University designed the multisector antenna for the indoor base station and implemented the simulation evaluation. NTT DOCOMO determined the specifications for the antenna and indoor base station, and  provided the measurement environment and implemented the demonstration. NIHON DENGYO KOSAKU commercialised the antenna while Fujitsu implemented the antennas in the 5G indoor base station.

Picture shows the antenna within a large anechoic chamber. And the same in close up.

DOCOMO previously measured the directivity of a single element in a multisector antenna in 2022, but believes that this was the world’s first demonstration to use a multisector antenna in a 5G base station equipped for radio beam control.

The antenna used in the demonstration contained 12 directional elements arranged in a radial pattern, transmitting and receiving radio waves in a specific direction. A Yagi-Uda antenna developed originally for television broadcasting was deployed for the high-frequency band. Conventionally, multiple multi-element planar-array antennas are required to propagate high-frequency radio waves to all areas of an indoor environment, requiring large circuitry that consumes significant amounts of energy and demands ample space for installation.

By using 5G-standardised beam-switching technology, however, the newly demonstrated multisector antenna incorporated in a small base station managed to achieve high gain in all directions with minimised energy consumption. Installing the envisioned device on ceilings will help to deliver high-frequency radio waves effectively throughout each room, thus reducing the number of base stations needed to construct high-quality indoor communication environments.

High-frequency radio waves have strong linearity and their strength tends to diminish easily, making it difficult to deliver such waves over wide areas. Conventionally, four or more base station antennas are required to transmit radio waves in all directions in a room, but the recent demonstration has now shown that just one multisector antenna can handle the task.

Going forward, DOCOMO plans to conduct verification tests using the new base station in various indoor environments, based on which it intends to finalize the antenna circuitry and incorporate it in commercial base stations for the establishment of high-quality indoor communication environments at a reduced cost.