Impact of RF I/Q Imbalance on Interference-Limited Mixed RF/FSO TWR Systems with Non-Zero Boresight Error

TL;DR

This paper analyzes how RF I/Q imbalance affects the performance of a dual-hop RF/FSO two-way relay system with interference, considering non-zero boresight error and turbulence effects, providing closed-form and asymptotic expressions for outage and throughput.

Contribution

It introduces a comprehensive model incorporating RF I/Q imbalance, interference, and optical pointing errors, deriving closed-form PDFs and asymptotic expressions for system reliability and throughput.

Findings

RF I/Q imbalance degrades system reliability and throughput.

Interference strength significantly impacts outage probability.

Non-zero boresight error influences FSO link performance.

Abstract

In this letter, we investigate a generic model assessing the effect of in-phase/quadrature-phase imbalance (IQI) on an asymmetric dual hop radio frequency/free space optical (RF/FSO) two-way relay (TWR) system in the presence of multiple co-channel interferers (CCIs) at the relay. The fading on the RF and FSO links have been modeled using K-distribution and double generalized Gamma (D-GG) turbulence model, respectively. The impact of non-zero boresight pointing error and type of optical demodulation schemes have been considered on the FSO link. To this end, a closed-form probability density function (PDF) has been derived for the FSO link undergoing D-GG irradiance with non-zero boresight pointing error. Furthermore, the exact and high signal-to-noise (SNR) asymptotic expression for outage probability have been presented. To gain insights into the throughput of the system, approximate and asymptotic expressions for the achievable sum rate (ASR) have been derived. The results show dependency of reliability and throughput offered on IQI at the RF front-end and strength of interference for the considered TWR system.