Mitsubishi Electric and NTT Docomo have achieved a 5G proof of concept for 27 Gbps and 25 Gbps maximum throughputs via one mobile terminal over communication distances of 32 feet and 328 feet, respectively, using 28 GHz. The demonstration was conducted during joint outdoor field trials using 28 GHz-band massive-element antenna systems and 16-beam spatial-multiplexing technology with 500-megahertz bandwidth. The trial took place in Kamakura, Kanagawa Prefecture Japan in September.
For outdoor trials using the 28 GHz band, Mitsubishi Electric used an antenna system with 16-beam spatial-multiplexing technology. Base-station antennas installed on the wall of a building directed beams to mobile-terminal antennas installed on the rooftop of a vehicle. The companies claim the trial was the world’s first successful wireless downlink transmission at those data rates.
A requirement of 5G is a peak data rate of 20 Gbps, according to Mitsubishi, which can be met by using massive-element antenna systems technology. Multi-beam spatial multiplexing allows multiple data streams to be transmitted in parallel to mobile terminals. Realizing this technology, however, has involved two challenges: implementation of a massive-element antenna array that clusters large numbers of antenna elements for high-precision beamforming, and mitigation of inter-beam interference.
Commissioned by Japan’s Ministry of Internal Affairs and Communications, Mitsubishi and Docomo focused their research on wideband massive MIMO and beam-control technologies for high SHF bands. To realize 20 Gbps throughput using 500-megahertz bandwidth, the two companies collaboratively developed and validated a massive-element antenna system enabling 16-beam spatial multiplexing.
The beam-forming technology enables beams to track a mobile terminal by switching the preset beam. The inter-beam interference reduction technology estimates the channel at the base station and controls the transmitting signal to adaptively reduce inter-beam interference as channel conditions over time. Together, the two technologies enable 16-beam spatial multiplexing in outdoor mobile environments.
The achieved peak data rates correspond to spectral efficiency of 67bps/Hz, believed to be the world’s best performance for 28 GHz-band mobile telecommunication.