Dynamic-subarray with Quantized- and Fixed-phase Shifters for Terahertz Hybrid Beamforming

Hybrid beamforming for terahertz (THz) communications is a promising technology for beyond 5G wireless systems, which has great potential to overcome very high propagation loss, mitigate hardware complexity, and achieve unprecedented data rates. In this paper, a dynamic-subarray (DS) architecture is investigated for THz hybrid beamforming systems. Specifically, we analyze both quantized-phase shifters (QPS) with finite phase levels, and fixed-phase shifters (FPS) with unaltered phases in the DS architecture, which significantly reduce hardware complexity and power consumption compared to using the infinite-resolution phase shifters (IPS). Furthermore, a generic low-complexity row-by-row (RBR) algorithm is derived for the proposed DS-structured hybrid beamforming with QPS and FPS. Extensive simulation results demonstrate that the RBR algorithm improves spectral efficiency and substantially reduces computational complexity. Compared to the DS-IPS, the DS-QPS architecture can achieve 98% spectral efficiency and 136% energy efficiency. In addition, we show that while the spectral efficiency of the DS-FPS architecture is 21% lower than the DS-QPS counterpart, the low-cost FPS provides 30% higher energy efficiency than QPS.