Hybrid mmWave MIMO Systems under Hardware Impairments and Beam Squint: Channel Model and Dictionary Learning-aided Configuration

TL;DR

This paper develops a comprehensive channel model for hybrid mmWave MIMO systems that includes hardware impairments and beam squint, and proposes dictionary learning and CS algorithms for accurate, low-overhead channel estimation in realistic conditions.

Contribution

It introduces a general channel model considering hardware impairments and beam squint, and proposes a dictionary learning-based approach for improved channel estimation.

Findings

The proposed algorithms outperform existing methods in realistic mmWave scenarios.

The dictionary learning effectively captures hardware impairments and beam squint effects.

Channel estimation accuracy is high with low complexity in simulations.

Abstract

Low overhead channel estimation based on compressive sensing (CS) has been widely investigated for hybrid wideband millimeter wave (mmWave) multiple-input multiple-output (MIMO) systems. The channel sparsifying dictionaries used in prior work are built from ideal array response vectors evaluated on discrete angles of arrival/departure. In addition, these dictionaries are assumed to be the same for all subcarriers, without considering the impacts of hardware impairments and beam squint. In this manuscript, we derive a general channel and signal model that explicitly incorporates the impacts of hardware impairments, practical pulse shaping functions, and beam squint, overcoming the limitations of mmWave MIMO channel and signal models commonly used in previous work. Then, we propose a dictionary learning (DL) algorithm to obtain the sparsifying dictionaries embedding hardware impairments, by considering the effect of beam squint without introducing it into the learning process. We also design a novel CS channel estimation algorithm under beam squint and hardware impairments, where the channel structures at different subcarriers are exploited to enable channel parameter estimation with low complexity and high accuracy. Numerical results demonstrate the effectiveness of the proposed DL and channel estimation strategy when applied to realistic mmWave channels.