Gaussian Phase Noise Effects on Hybrid Precoding MIMO Systems for Sub-THz Transmission

TL;DR

This paper investigates how Gaussian phase noise affects hybrid precoding MIMO systems at sub-THz frequencies, providing analytical bounds and simulation validation for system performance under hardware impairments.

Contribution

It derives a lower bound on spectral efficiency and closed-form BER expressions for GPN-affected MIMO systems using hybrid precoding, with validation through simulations.

Findings

GPN can be mitigated with a single pilot in single-user MIMO.

Analytical bounds match simulation results under high-SNR conditions.

Polar-QAM outperforms conventional QAM in GPN-affected systems.

Abstract

The sub-THz spectrum offers numerous advantages, including massive multiple-input multiple-output (MIMO) technology with large antenna arrays that enhance spectral efficiency (SE) of future systems. Hybrid precoding (HP) thus emerges as a cost-effective alternative to fully digital precoding regarding complexity and energy consumption. However, sub-THz frequencies introduce hardware challenges, particularly phase noise (PN) from local oscillators (LOs). We analyze PN impact on MIMO systems using HP, leveraging singular value decomposition and common LO architecture. We adopt the Gaussian PN (GPN) model, recognized as accurate for describing PN behavior in sub-THz transmissions. We derive a lower bound on achievable SE and provide closed-form bit error rate expressions for quadrature amplitude modulation (QAM), specifically 4-QAM and 16-QAM, under high-SNR and strong GPN conditions. These analytical results are validated through Monte Carlo simulations. We show that GPN can be effectively counteracted with a single pilot symbol in single-user MIMO systems, unlike single-input single-output systems where mitigation proves infeasible. Simulation results compare conventional QAM against polar-QAM tailored for GPN-impaired systems. Finally, we introduce perspectives for further improvements in performance and energy efficiency.