On The Joint Effects of HPA Nonlinearities and IQ Imbalance On Mixed RF/FSO Cooperative Systems

TL;DR

This paper analyzes the impact of HPA nonlinearities and IQ imbalance on the performance of dual-hop RF/FSO MIMO relay systems, providing analytical expressions and insights into system robustness under impairments.

Contribution

It introduces a comprehensive analytical framework for assessing the effects of HPA nonlinearities and IQ imbalance in hybrid RF/FSO MIMO systems, including performance metrics and asymptotic analysis.

Findings

HPA nonlinearities and IQ imbalance significantly affect system performance.

Derived closed-form expressions for outage probability, BER, and capacity.

Validated analytical results with Monte Carlo simulations.

Abstract

In this work, we provide a framework analysis of dual-hop hybrid Millimeter Wave Radio Frequency (RF)/Free Space Optical (FSO) MIMO relaying system. The source is equipped with multiple antennas and employs conjugate beamforming while the destination consists of multiple apertures with selection combining. The system also consists of a relay operating at amplify-and-forward mode. The RF channels are subject to Nakagami-m fading while the optical links experience the M\'alaga distribution. In addition, we introduce the impairments to the relay and receiver. In fact, the relay is impaired by the High Power Amplifier (HPA) nonlinearities while the receiver suffers from the In phase and Quadrature Imbalance. Moreover, we assume two types of HPA nonlinearities impairments called Soft Envelope Limiter (SEL) and Traveling Wave Tube Amplifier (TWTA). Closed-forms of the outage probability, the bit error probability, and the ergodic capacity are derived. Capitalizing on these performances, we derive the high SNR asymptotes to unpack insightful metrics such as the diversity gain. We also address the impacts of some key factors on the system performance such as the impairments, the interferers, the number of antennas and apertures and the pointing errors, etc. Finally, the analytical expressions are confirmed by Monte Carlo simulation.