Sensing-Assisted Beam-Focusing for Terahertz Near-Field Mobile Communications: A Closed-Form Framework

Terahertz (THz) band is acknowledged as a candidate spectrum in future networks. However, THz communications demand the assistance of high-accuracy parameter estimations to achieve narrow beam-alignment. Despite existing works have intensively explored sensing-assisted THz communications, they fail in mobile and near-field scenarios without concerning the benefits brought from velocity and distance estimations. To this end, a closed-form framework toward sensing-assisted terahertz near-field mobile communications (SA-TNMC) is introduced in this paper. Four-dimensional parameters containing distance, azimuth angle, radial velocity, and tangential angular velocity are extracted from the echoes, all of which are utilized for beamfocusing. For performance characterizations, both Cramér-Rao Bound and Ergodic Shannon Capacity are derived in closedform expressions. Besides, a novel critical point is proposed to demarcate the minimized resource division factor to activate SA-TNMC system. At last, numerical results are proceeded to validate the framework.