NEC Corporation has successfully transmitted digital beamforming with a massive-element active antenna base station system that supports 28 GHz band for 5G communications. This is the first time simultaneous beamforming transmission (four multi-users MIMO) from a single massive-element active antenna system (AAS) to four terminals has been successfully demonstrated. NEC achieved a 3.1 Gbps cell throughput by using a frequency bandwidth of 300 MHz in the test.
NEC's massive-element AAS (active antenna system), for the 28 GHz band, adopts a fully digital control system, which improves the precision of beamforming. The fully digital control system enables simultaneous beamforming in multiple directions from a single massive-element AAS unit and efficiently implements high-speed and high-capacity communication without interfering with adjacent users through spatial multiplexing. In contrast, analog control systems require the installation of the same number of massive-element AASs as the number of beams, creating the issue of a larger footprint.
This digital control system is also capable of beamforming that takes into account multipath, a non-direct wave signal, and moderately adjusts beam directions to implement high-quality communication. This is in addition to beamforming that cancels out interference through multipath and reduces performance deterioration caused by inter-cell interference. Fully digital control systems traditionally require a number of digital/analog signal and frequency converters. This generally increases power consumption, capacity and cost for the entire system. NEC, however, has successfully developed a massive-element AAS that adopts a fully digital control system with less power and more compact conversion functions through NEC's original technology.
In order to effectively implement sophisticated services that apply 5G features from 2020 onward, it is essential to utilize 28 GHz and other high frequency radio bands, which enable the securing of wide bandwidth, and the utilization of beamforming. Moving forward, NEC will continue its efforts in development and demonstration tests for a massive-element active antenna base station systems that delivers high speed, high capacity and massive connectivity.
