NEC claims mmWave distributed-MIMO technique triples simultaneous connections in office environments

Tokyo, January 25, 2021 - NEC Corporation (NEC; TSE: 6701) announced today it has demonstrated multiple highly stable simultaneous terminal connections and transmission capacity in a real office environment through distributed-MIMO (*1) in the 28 GHz millimeter-wave frequency band. This demonstration achieved approximately 3 times the number of simultaneous connections and transmission capacity compared to cases without distributed-MIMO in the 28 GHz frequency band. Moreover, transmission deterioration from obstacles was also reduced.

According to NEC research, this is the first demonstration in the industry to apply a distributed-MIMO system in the millimeter-wave frequency band in an office environment. This is expected to contribute to the construction of highly convenient 5G environments that enable simultaneous multiple connections in the future.

Earlier this year, Japan began to commercially deploy 5G in the sub 6 frequency band and millimeter-wave frequency band, with the expectation of enhancing network performance to support 10 times more capacity than 4G, as well as higher throughput, lower latency, and multiple connections.

However, since the usable frequency band of the sub 6 frequency band is more narrow than in the millimeter-wave frequency band, Massive-MIMO (*2) systems have been introduced to expand capacity and increase the number of simultaneously connected terminals. Applying Massive-MIMO techniques to millimeter-wave frequency is considered to be optimal for applications where each terminal requires a high transmission capacity, such as indoor offices or stadium seats with high terminal density.

However, in the millimeter-wave frequency band, challenges to applying Massive-MIMO techniques include difficulty in achieving stable connections and spatial multiplexing due to the characteristics of radio waves, such as short wavelength and large attenuation due to reflection and shielding.

NEC has established itself as a leader in digital beamforming technology and has commercialized Massive-MIMO in the sub 6 frequency band (*3). Moreover, NEC has developed digital coordination technology among antenna elements distributed in the millimeter-wave frequency band and conducted verification activities to solve the problems of indoor mobile communications, such as shadowing and diffraction of propagation paths (*4).

Against this background, NEC conducted propagation and transmission trials in a real office environment using a distributed-MIMO technique for the Radio Units (RU) of a 28 GHz band base station system, demonstrating simultaneous connections with multiple terminals and increased capacity. Specifically, NEC developed a technology to effectively calibrate phase and amplitude in response to the difficulty in calibrating and coordinating the phase and amplitude between distributed antennas. As a result, NEC achieved approximately 3 times the number of simultaneous connections and transmission capacity when compared to cases where a distributed-MIMO system is not used.

NEC will continue to carry out 5G demonstration experiments for enabling stable and high transmission speeds in environments where stable millimeter-wave communication is difficult due to obstacles and densely arranged terminals, such as offices and stadium seating, aiming to contribute to the development of millimeter-wave mobile access networks and building ecosystems among operators and venders.

Furthermore, NEC will continue its initiatives for creating new social value by providing "NEC Smart Connectivity" (*5) for connecting data generated by people and things and reaching beyond conventional thinking in support of network performance.

Attachment: About the Distributed-MIMO Demonstration