Energy-Efficient Design of Indoor mmWave and Sub-THz Systems With Antenna Arrays

Emerging millimeter-wave ( mmWave) and Terahertz ( THz) systems is a promising revolution for next-generation wireless communications. In this paper, we study an indoor multi-user mmWave and sub-THz system with large antenna arrays, where two different types of architecture, the fully-connected structure and the array-of-subarray structure, are investigated. Specifically, the Doherty power amplifier ( PA) is adopted to improve the PA efficiency of the system, and the associated nonlinear system power consumption models with insertion power loss are developed. By capturing the characteristics of the mmWave and sub-THz channels, we design different hybrid beamforming schemes for the two structures with low complexity. We further compare the achievable rates of the two structures and show that, with the insertion loss, the achievable rate of the array-of-subarray structure is generally larger than that of the fully-connected structure. Moreover, we propose the optimal power control strategies for both structures to maximize the energy efficiency of the system and demonstrate that the energy efficiency of the array-of-subarray structure outperforms that of the fully-connected structure. Simulation results are provided to compare and validate the performance of the two structures, where the array-of-subarray structure shows a great advantage over the fully-connected structure in both spectral efficiency and energy efficiency.