Multi-User Long-Distance sub-THz Wireless Communication

In this paper we present the first point-to-multipoint sub-THz wireless communication link capable of simultaneously transmitting data to multiple users over several meters at tens of gigabits per second. The sub-THz wireless link employs an optoelectronic transmitter that generates digital subcarriers by modulating a single free-running laser with a high-bandwidth electro-optic IQ modulator. A uni-traveling-carrier photodiode downconverts the transmitted signal from the optical to the sub-THz domain, and the signal is transmitted by a lens-integrated leaky-wave antenna, offering a gain of up to 30 dBi and a wide beam-steering range of approximately 51 degrees in the horizontal plane. The optoelectronic transmitter can simultaneously address multiple receiver units, i.e., users, hence enabling efficient multi-user operation. A sub-THz electronic receiver unit operating from 280 to 320 GHz is used for reception. In a proof-of-concept experiment, the sub-THz wireless link is implemented in a lecture hall scenario with one transmitter and two receiver units. The distance between the transmitter and receivers is 16 m, with the two receivers having a maximum spacing of 3.3 m. Measurements have been conducted for single-, dual-, and up to four-user configurations using QPSK and 16-QAM modulation schemes. To the best of the authors' knowledge, record-high data rates of up to 80 Gbps for a single-user, 40 Gbps for dual-users, and 20 Gbps for four users are demonstrated for the first time in a sub-THz point-to-multipoint system. %While long-distance, high-data-rate communications of up to hundreds of gigabits per second over distances exceeding 50 meters have been demonstrated for point-to-point links, only short distances with relatively lower data rates have been experimentally validated for point-to-multipoint links at sub-THz frequencies. To the best of the authors' knowledge, this paper presents the first sub-THz wireless communication link that simultaneously transmits data to up to four users at a record-breaking data rate of up to 80 Gbps for a single user over a distance of 16 meters in an indoor lecture hall scenario. The sub-THz wireless link uses an optoelectronic transmitter with a uni-traveling carrier photodiode that downconverts the transmit signal from the fiber-based optical domain to the sub-THz frequency domain. For transmission a high-gain and lens-integrated leaky-wave antenna, that provides multiple beams and simultaneously transmits data to multiple receiver units, i.e., users is employed. Sub-THz electronic receiver units operating from 280 to 320 GHz are used for a multi-user reception.