NEC Develops Millimeter-wave Distributed Antenna Radio Unit Improving the Channel Quality for Indoor 5G Applications

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NEC Corporation, a leader in the integration of IT and network technologies, today announced the development of millimeter-wave(1) distributed antennas for the efficient use of 5G millimeter-wave spectrum (28GHz band) for the first time. Demonstration experiments were conducted with this technology at the NEC Tamagawa Plant in 2019, where the capability of high-speed, large-capacity communications with stable propagation channel quality was confirmed.

In terms of background, 5G uses millimeter waves, which have frequency bands more than 10 times higher than 4G, and are expected to contribute to a wide range of services that provide high-speed, large-capacity, low-latency, and multiple connections. Due to the nature of millimeter waves, however, communication quality is susceptible to deterioration due to shielding and interference caused by obstacles and installations. As a result, it is necessary to establish a large number of base stations to ensure communication quality. However, in places with limited space, such as homes and workplaces, there is also a need to downsize base stations.

To resolve these challenges, NEC developed digital coordination technologies to connect distributed antenna elements for wireless satellite stations (RU: Radio Unit) of 5G millimeter-wave (28GHz-band) base stations. Moreover, NEC resolved the issues of shielding and diffraction of propagation paths for interior mobile communications using millimeter-wave communication. This technology applies NEC's proprietary massive MIMO(2), which combines a large number of independent antennas, in order to deliver millimeter-wave high-speed, high-capacity communications with stable communication quality.

In addition, by connecting distributed antennas to control units using a frequency multiplexer that consolidates multiple signals, NEC resolved issues related to attenuation, synchronization and power supply that might arise when connecting antennas and control units with high-frequency cable or optical cable, thereby helping to facilitate the installation of antennas. Furthermore, NEC has produced smaller antennas (approximately 5cmx2cm with 8 components) by designing and implementing circuits cultivated through NEC's iPASOLINK microwave communication system.

NEC's demonstration experiment consisted of a system with eight antennas, a control unit for controlling antennas, and a baseband processing unit that controls antennas.

In the experiment, NEC applied digital beamforming(3), which had been developed in the sub-6GHz and millimeter bands, to 28GHz band antennas. By combining and multiplying the space of radio waves, NEC achieved not only high-speed, high-capacity communication, but also stabilized the propagation path. NEC also achieved stable communications in difficult propagation environments, such as shadowing by walls, interference from reflective waves, and environments where multiple terminals are closely linked.

Going forward, NEC will continue to conduct demonstration tests in various environments, such as office buildings, commercial facilities, and factories, with the aim of commercializing this technology by the end of 2020.

NEC will announce details of a feasibility study on this technology at IEEE Radio Wireless Week 2020 held in San Antonio, Texas, USA, from January 26 to 29. NEC will also exhibit this technology at a MWC Barcelona 2020 in Barcelona, Spain, from February 24 to 27.

Under NEC's Mid-term Management Plan 2020, which covers the three-year period to FY2020, NEC is promoting service businesses in new areas that leverage the strengths of its network technologies. Through these developments, NEC will accelerate the provision of "NEC Smart Connectivity"(5) utilizing network flexibly to dynamically link data produced by people and goods across industries, and to create new social value.