We investigate the performance of a dual-hop mixed radio frequency (RF)/free space optical (FSO) system with variable-gain relaying. The RF link is modeled by the $\kappa$ - $\mu$ shadowed distribution, which unifies popular RF channel models. The FSO link is subject to atmospheric turbulence with non-zero boresight pointing errors. The atmospheric turbulence channel is modeled by the Fisher-Snedecor ${\mathcal F}$ distribution, which fits well with the measurement data under weak-to-strong turbulence conditions. The pointing error is modeled by the Beckmann distribution, which includes popular pointing error models. We propose an approximation method to approximate the $\kappa$ - $\mu$ shadowed distribution using an $\alpha$ - $\mu$ distribution, which is more accurate than that using a gamma distribution in the existing literatures. Then, we derive closed-form expressions for the probability density function (PDF) and the cumulative distribution function (CDF) for the irradiance fluctuations. Based on these expressions, we derive closed-form approximate expressions for the CDF, the PDF, the moment generating function (MGF), the average bit error rate (BER), and the ergodic capacity (EC) of the considered system in terms of the bivariate Fox’s H function. Furthermore, asymptotic expressions for the CDF and the average BER at high signal-to-noise ratio (SNR) are derived in terms of simple elementary functions. Finally, numerical results and Monte Carlo (MC) simulations are provided to verify the derived approximate expressions.

In this paper, we numerically study the secrecy performance of the free-space optical (FSO) system by considering different eavesdropping scenarios. More precisely, we considered three possible eavesdropping scenarios for Eve: 1) Eve is between Alice and Bob; 2) Eve and Bob are in the same receiving plane; 3) Eve is behind Bob. We adopt the Málaga ( M )-distribution channel to model atmospheric turbulence due to the presence of link blockage while considering the non-zero boresight pointing error and path loss. To do so, we obtain a novel probability density function (PDF) and cumulative distribution function (CDF) under different eavesdropping scenarios, based on which we derived the secrecy outage probability (SOP) analytical expressions as well as their asymptotic expressions at a high SNR regime. We verified the results using Monte Carlo simulations, which showed that the parameters related to atmospheric turbulence and pointing errors, as well as the location of the eavesdropper, have different effects on different eavesdropping scenarios.

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The performance of a dual-hop mixed radio frequency (RF)/free space optical (FSO) system with co-channel interferences (CCIs) is studied for both fixed-gain and variable-gain amplify-and-forward(AF) relaying scenarios. The RF link and interference link undergo the $\kappa$ - $\mu$ shadowed fading and the FSO link experiences the Fisher-Snedecor ${\cal F}$ distribution with pointing errors. For the considered system, we derive new closed-form expressions for the probability density function (PDF), cumulative distribution function (CDF), and average bit error rate (BER) of the end-to-end signal-to-interference-plus-noise ratio (SINR). In addition, efficient numerical expressions for the ergodic capacity are also obtained. Moveover, the asymptotic expressions for the CDF and average BER are derived. Our results can be regarded as a generalization of the previous results. Finally, numerical and simulation results are presented to verify the correctness of the proposed expressions.

We investigate the performance of a dual-hop mixed free space optical (FSO) /radio frequency (RF) system with fixed-gain relaying under direct detection and heterodyne detection techniques. The FSO link is modeled by the Fisher–Snedecor F distribution, which matches well with the experimental data under weak-to-strong turbulence regimes. The RF link experiences κ − μ shadowed fading, which unifies popular RF fading models. The κ − μ shadowed distribution is approximated by an α − μ distribution. Capitalizing on this approximation, closed-form approximate expressions for the cumulative distribution function, the average bit error rate of different modulation schemes, and the ergodic capacity are derived in terms of the bivariate Fox’s H function. Moreover, asymptotic analysis is carried out at a high signal-to-noise ratio to further illustrate the obtained diversity order and the influence of system and channel parameters. Numerical results and Monte Carlo simulations are presented to validate the derived approximate expressions.

This paper investigates the performance of interference-limited and interference-free dual-hop mixed radio frequency (RF)/free space optical (FSO) systems with partial relay selection (PRS) for the variable-gain (VG) amplify-and-forward (AF) relaying scenario. We concentrate on the generalized channel model that not only describes different application scenarios but also allows a more accurate description of the channel characteristics. Specifically, the PRS-aided RF link is modeled by the κ-μ shadowed distribution, and the FSO link is expressed in terms of Fox’s H-function, which unifies Fisher-Snedecor F, Gamma-Gamma (GG), and Malága (M) distributions for atmospheric turbulence along with pointing errors and detection modes. The interference signals at the selected relay are modeled by independent identically κ-μ shadowed distributions. Using our analytical framework, new unified closed-form expressions for the cumulative distribution function (CDF), the average bit error rate (BER), and the ergodic capacity are derived. Additionally, we provide asymptotic expressions of the average BER at high SNR. The analysis quantifies the impact of co-channel interference, pointing errors, number of relays, and rank of the selected relay on the considered system’s performance. Finally, numerical results and Monte Carlo (MC) simulations are presented to confirm the effectiveness of the derived expressions. Note that our results provide a generalized framework for comprehensive studies of this kind of systems.