In this paper, an alternative implementation for the hybrid free space optical (FSO)/radio frequency (RF) wireless communication system without requiring channel state information is presented. The proposed hybrid system transmits the same data with the same data rate over both links simultaneously. The well-known diversity selection combining scheme is implemented to combine the received signals in the electrical domain. New closed-form expressions for the average bit error rate and outage probability are derived in order to trace the system's performance over various channel turbulence conditions. The analysis of the proposed system's performance clearly indicates that the proposed system is advantageous as it exploits the complementary properties of the FSO and RF channels, even in strong turbulence conditions. In addition, the performance comparison demonstrates the proposed system's superior performance compared with the FSO-only system

In this paper, the secrecy performance of the physical layer security (PLS) of the hybrid free-space optical/radio frequency (FSO/RF) communication system is analyzed. The transmission protocol of the considered system is performed under the eavesdropper’s attempt to overhear the RF link between the legitimate transmitter and receiver of the hybrid system. The FSO link is characterized by Málaga-M distribution while the RF links are modeled by Nakagami-m distribution. The two practical eavesdropping modes considered in this paper include: colluding and non-colluding. Exact closed-form expressions for the system’s secrecy outage probability (SOP), the asymptotic of the SOP (SOP∞), the probability of strictly positive secrecy capacity (SPSC), and the average secrecy capacity (ASC) are specifically derived under the influence of both eavesdropper modes. Our derived analytical expressions present an efficient tool to investigate the impact of some channel parameters on the secrecy performance, namely the fading severity of the RF links, atmospheric turbulence severity, pointing error of the FSO link, number of eavesdroppers, and the power of the eavesdropper links. The results show that the increase of the eavesdroppers’ number under both modes profoundly degrades the considered system secrecy performance. The accuracy of the numerical results obtained is validated by Monte-Carlo simulations.

In this work, the author investigate the performance of the hybrid free‐space optical/radio frequency (FSO/RF) communication systems where RF links are subject to Nakagami‐m distribution fading effects. The author derive the statistical characteristics of the hybrid FSO/RF systems in closed‐form in terms of Meijer's G‐function and the extended generalised bivariate Meijer's G‐function. Then, the author rely on these new results to present the performance analysis of the selection combining diversity based on hybrid FSO/RF systems. Also, the author consider a Gamma–Gamma turbulence distribution under the impact of pointing errors and subject to both types of detection techniques (i.e. heterodyne detection and intensity modulation with direct detection (IM/DD)) in the FSO link. Computer‐based Monte–Carlo simulations are proved the accuracy of the new analytical results.

In this paper, we develop an innovative series representation for the sum of Rician non-zero boresight pointing error random variates based on the k - μ distribution, which is suitable for multiple-input multiple-output (MIMO) transmission for the first time. Then, using this new representation, we introduce a novel closed-form probability density function (PDF) approximation for the sum of Gamma-Gamma random variates with generalized pointing errors and atmospheric attenuation of MIMO free-space optical (FSO) communications. Statistical Kolmogorov-Smirnov tests confirm the accuracy of this approximation over a wide range of channel conditions. The significance of this approximation is emphasized by deriving closed-form expressions for the ergodic capacity, outage probability, and average bit error rate (BER) using Meijer's G-function. This paper provides a comprehensive analysis of the performance of MIMO FSO systems utilizing the equal gain combining (EGC) diversity technique under various conditions, such as different numbers of transmitter and receiver, turbulence intensities, the effects of non-zero boresight pointing errors, and path attenuation. The results show that using MIMO technology with more transmitters and receivers significantly improves the performance of FSO communication compared to other diversity techniques, including single input single output (SISO), and multiple input single output (MISO) systems. Detailed evaluations of the ergodic capacity, outage probability, and average BER performance at high signal-to-noise ratios provide additional insights. Monte-Carlo simulation results demonstrate the accuracy of the proposed approach.

This paper presents a secrecy performance analysis of a parallel free-space optical/millimeter-wave (mm-wave) communication system with a selection-combining receiver over a unified Fisher-Snedecor $\mathcal{F}$ -distribution channel. The $\mathcal{F}$ -distribution model, with the proper parameters, may be used to describe both the mm-wave and optical channels. The security performance is specifically evaluated by deriving closed-form expressions for the average secrecy capacity, secrecy outage probability, and strictly positive secrecy capacity. We examine the three following distinct security scenarios: 1) An FSO-link eavesdropping attack, 2) mm-wave-link eavesdropping attacks, and 3) eavesdropping attacks on FSO and mm-wave links at the same time. Furthermore, to better understand the influence of various system and channel parameters, asymptotic analysis is performed at high signal-to-noise ratio values. Our developed analytical expressions provide an efficient tool for examining the influence of various system and channel parameters on the secrecy performance, including the atmospheric turbulence severity, pointing errors of the FSO link, fading severity, the shadowing parameters, as well as the number of diversity branches of the mm-wave links. Monte-Carlo simulations are used to verify the correctness of the numerical findings.