Sub-band Assignment and Power Allocation with Beam Multiplexing and Aggregation in Terahertz Communications

Abstract

The beam split effect (BSE) can result in a serious loss in achievable rate in terahertz (THz) transmission. In this work, we propose a new sub-band assignment scheme in a multiuser THz communications system to address the BSE. We consider a base station employs true-time-delay hardware between radio frequency chains and uniform planar arrays (UPAs). The core idea of this hardware is that, rather than fine-tuning the UPA delays to form a single beam from each UPA, we facilitate multi-beam transmission from each UPA. We derive a novel expression for the maximum sub-band bandwidth for UPA, ensuring that the BSE is avoided within each beam. Based on this expression we design sub-band assignment across users and power allocation among sub-bands to maximize the sum-rate, relying on the principles of beam multiplexing and aggregation (BMA). Using numerical results, we demonstrate (i) the merits of our proposed sub-band assignment in contrast to the distance-aware sub-band assignment scheme, (ii) the effectiveness of BMA in comparison with the BSE, and (iii) the improved performance resulting from our proposed optimal power allocation relative to equal power allocation. Show more