Omni-Directional Signal Broadcasting for Terahertz Communications in 6G Mobile Systems

To realize a unprecedentedly high data speed in terabits-per-second (Tbps), the upcoming sixth-generation (6G) mobile communications system needs to utilize the abundant spectrum in the terahertz bands. However, high-frequency transmission suffers severe propagation loss and short transmission distance, which would be heavily relies on a large-scale antenna array to reap high beamforming gain, used to compensate for such a loss. But beamforming over an antenna array, especially a large-scale array, raises a problem of omni-directional coverage during the phase of initial access, where a base station is required to broadcast synchronization signals and master system information to each user within its coverage. Therefore, this paper aims to propose a novel omni-directional beamforming scheme, providing instantaneous gain equally in all directions by forming a pair of complementary beams. Numerical results verify that it can achieve omni-directional coverage with the optimal performance that remarkably outperforms the previous scheme called random beamforming.