Millidegree-Level Direction-of-Arrival (DoA) Estimation and Tracking for Terahertz Wireless Communications

The Terahertz (0.1-10 THz) band is envisioned to meet the rapid growth of wireless data rates. Achieving high beamforming gain and reduced hardware complexity, the array-of-subarrays (AoSA) hybrid beamforming is a promising technology to be adopted for THz communications. The generated razor-sharp beam can compensate for the severe path loss and overcome the distance limitation. However, major challenges in the THz hybrid beamforming system include millidegree-level three-dimensional (3D) angle estimation, and overhead reduction beam tracking. To solve these challenges, an off-grid ultra-high-resolution direction-of-arrival (DoA) estimation method that matches the AoSA architecture, namely, AoSA-MUSIC, is developed in this paper, which involves coarse and refine training. Furthermore, an extended DoA tracking method, namely, AoSA-MUSIC-T, is developed, which employs a subspace tracking scheme with the overhead reduced tracking observation to replace the high-complexity eigenvalue decomposition (EVD) process in the AoSA-MUSIC method. Simulation results show that the proposed AoSA-MUSIC can obtain millidegree-level precise DoA estimation. Moreover, the AoSA-MUSIC-T tracking algorithm can capture the fleeting DoA variation in millisecond with fifty-percent reduced training overhead.