High-Speed Uplink Data Wireless Transmission via a Frequency Conversion Relay Device from the Terahertz to the Millimeter-Wave Toward Beyond 5G Mobile Communication

This paper presents the results of a demonstration experiment aimed at achieving high-speed uplink transmission for Beyond 5G mobile communication via wireless transmission in both the terahertz band (252 to 296 GHz) and the millimeter-wave (mmWave) band (37.5 GHz). The demonstration system consists of terahertz transmitters that upconvert IF input signals with 4.8 GHz bandwidth orthogonal frequency-division multiplexing (OFDM) modulation mapped with quadrature phase-shift keying (QPSK) subcarriers and relay devices that downconvert the signals from the terahertz band to the mmWave band and transmit them to an access point (AP). Wireless transmission via dual V and H polarization was achieved at a line-of-sight distance of 0.3 m in the terahertz band and 5 m in the mmWave band, with a physical transmission speed of over 19 Gbps. Additionally, the experiment demonstrated that the received signal quality can be maintained by adjusting the beam direction of the terahertz antenna, even when the orientation of the relay device is changed. This demonstration offers prospects for achieving the ultrahigh-speed transmission expected in Beyond 5G mobile communication via a frequency conversion relay device from the terahertz band to the mmWave band.