Terahertz Beamforming and Group Sparse Channel Estimation Relying on Low-Resolution ADCs in MU Hybrid MIMO systems

TL;DR

This paper introduces a Bayesian learning framework for beamforming and channel estimation in wideband THz MU hybrid MIMO systems with low-resolution ADCs, addressing non-linear distortions and exploiting sparsity for improved performance.

Contribution

It proposes a novel Hierarchical Bayesian Group-sparse Regression method that leverages shared sparsity and Bussgang decomposition to enhance channel estimation and beamforming in practical THz systems.

Findings

The proposed estimator outperforms existing methods in accuracy.

The TTD-based beamforming effectively compensates beam-squint effects.

Simulation results demonstrate robustness under realistic system constraints.

Abstract

A unified beamforming and channel estimation framework relying on Bayesian learning is conceived. Recognizing the limitations imposed by low-resolution analog-to-digital converter (ADCs) and frequency-dependent propagation effects occurring in the Terahertz (THz) band, we formulate a dual-wideband channel model incorporating root raised cosine (RRC) pulse shaping. To address the non-linear distortions introduced by low-resolution ADCs, Bussgang decomposition is employed, leading to a tractable linearized inference process. By leveraging the shared sparsity inherent in a multi-user (MU) scenario of THz systems, we propose a Hierarchical Bayesian Group-sparse Regression (HBG-SR) based channel learning technique that exploits the group-sparse structure of THz band channels. The estimated dominant angle-of-arrival/ angle-of-departure (AoA/AoD) indices are then exploited for appropriately configuring the true-time-delay (TTD) elements in the hybrid transceiver, enabling precise beam alignment across subcarriers and the effective compensation of the beam-squint effect occurring in wideband THz systems. Extensive simulation results validate the efficiency of the proposed channel estimator and the TTD-aided beamforming architecture, highlighting their robustness and performance gains under practical wideband THz system constraints.