NEC Develops mmWave Distributed Antenna Radio Units to Improve Indoor 5G Performance

NEC Corporation, a leader in the integration of IT and network technologies, announced the development of millimeter-wave distributed antennas for efficient use of 5G millimeter-wave spectrum in the 28 GHz band. 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 were confirmed.

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 many 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 (28 GHz-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, 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 5cm×2cm 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, which had been developed in the sub-6 GHz and millimeter bands, to 28 GHz 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.

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” utilizing network flexibly to dynamically link data produced by people and goods across industries, and to create new social value.