# Partial Relay Selection For Hybrid RF/FSO Systems with Hardware Impairments

## TL;DR

This paper analyzes the performance of a dual-hop RF/FSO relaying system with hardware impairments, deriving new analytical expressions for outage probability and capacity, and examining the impact of various system parameters.

## Contribution

It introduces a comprehensive model including hardware impairments for hybrid RF/FSO systems and derives novel analytical expressions for key performance metrics.

## Key findings

- Hardware impairments cause a ceiling in SNDR at high SNR in non-ideal systems.
- Outage probability and capacity depend on relay number, CSI correlation, and atmospheric turbulence.
- Ideal hardware systems show unbounded SNDR growth with increasing SNR.

## Abstract

In this paper, we investigate the performance analysis of dual hop relaying system consisting of asymmetric Radio Frequency (RF)/Free Optical Space (FSO) links. The RF channels follow a Rayleigh distribution and the optical links are subject to Gamma-Gamma fading. We also introduce impairments to our model and we suggest Partial Relay Selection (PRS) protocol with Amplify-and-Forward (AF) fixed gain relaying. The benefits of employing optical communication with RF, is to increase the system transfer rate and thus improving the system bandwidth. Many previous research attempts assuming ideal hardware (source, relays, etc.) without impairments. In fact, this assumption is still valid for low-rate systems. However, these hardware impairments can no longer be neglected for high-rate systems in order to get consistent results. Novel analytical expressions of outage probability and ergodic capacity of our model are derived taking into account ideal and non-ideal hardware cases. Furthermore, we study the dependence of the outage probability and the system capacity considering, the effect of the correlation between the outdated CSI (Channel State Information) and the current source-relay link, the number of relays, the rank of the selected relay and the average optical Signal to Noise Ratio (SNR) over weak and strong atmospheric turbulence. We also demonstrate that for a non-ideal case, the end-to-end Signal to Noise plus Distortion Ratio (SNDR) has a certain ceiling for high SNR range. However, the SNDR grows infinitely for the ideal case and the ceiling caused by impairments no longer exists. Finally, numerical and simulation results are presented.