An Omni-Directional Coverage Scheme for Terahertz Communications with Hybrid Beamforming

In order to achieve a unprecedented terabits-per-second (Tbps) data rate in the sixth-generation (6G) mobile system, wireless communications require far more bandwidth, which cannot be available under the current spectrum-usage paradigm. Therefore, the 6G system has to exploit the abundant spectrum in the high-frequency bands, i.e., millimeter wave and terahertz (THz) frequencies. However, high-frequency transmission heavily relies on high beamforming gain to compensate for severe propagation loss and to extend its transmission distance. A beam-based system faces a barrier in the process of initial access, where a base station must broadcast synchronization signals and system information to all users within its coverage. Hence, this paper aims to propose a novel omnidirectional coverage scheme for THz communications with hybrid beamforming. It provides an instantaneously equal gain over all directions by forming complementary beams over sub-arrays. Numerical results verify that it can achieve omnidirectional coverage with a performance that remarkably outperforms the previous scheme.