Distance-aware coordinated multi-point transmission for terahertz band communication

Terahertz (THz) band communication has abundant spectral resources to accommodate multiple broadband carriers. However, the strong path loss attenuation and the limited transmission power affect the maximum number of carriers that can be activated. A simple way to address this limitation consists in transmitting the same message from multiple transmission points, using Joint-Transmission (JT) Coordinated Multi-Point (CoMP). However, the distance-frequency-dependent molecular absorption that THz channels experience makes the implementation of JT-CoMP challenging. In this paper, we propose a decentralized scheme that takes into account the effect of distance to select the per-carrier transmit beamforming weights and powers. For this purpose, low-rate feedback information is reported from the receiver to the transmission points, such that decisions performed locally take into account the ones made in the coordinated set. Notable sum data rate gains are observed when compared to the baseline schemes, where transmission power is equally divided among carriers or independently allocated using waterfilling. As expected, the accuracy of the reported channel phase information, the number active transmission points, and the distance-dependent frequency selectivity of the THz channel affect the sum data rate that multi-carrier JT-CoMP can provide.