Nowadays, the hybrid automatic retransmission request (H-ARQ) protocols are prevalent in fifth-generation (5G) and beyond communications. The utilization of H-ARQ protocols is extended to free-space optical (FSO) communication systems to achieve a reliable link. In this paper, we investigate the secrecy performance of chase combining (CC) H-ARQ protocol in the presence of an eavesdropper. We present the closed-form expressions of the average secrecy capacity (ASC) and secrecy outage probability (SOP) of FSO systems over atmospheric turbulence-induced fading channels and different rounds of H-ARQ transmission. We also derive the conditional SOP and secrecy throughput of the considered FSO system. The expressions are valid for weak to strong atmospheric turbulence, intensity modulation direct detection, and different number of H-ARQ rounds. We have also validated our proposed results using Monte Carlo simulations.
Nowadays, the hybrid automatic retransmission request (H-ARQ) protocols are prevalent in fifth-generation (5G) and beyond communications. The utilization of H-ARQ protocols is extended to free-space optical (FSO) communication systems to achieve a reliable link. In this paper, we investigate the secrecy performance of chase combining (CC) H-ARQ protocol in the presence of an eavesdropper. We present the closed-form expressions of the average secrecy capacity (ASC) and secrecy outage probability (SOP) of FSO systems over atmospheric turbulence-induced fading channels and different rounds of H-ARQ transmission. We also derive the conditional SOP and secrecy throughput of the considered FSO system. The expressions are valid for weak to strong atmospheric turbulence, intensity modulation direct detection, and different number of H-ARQ rounds. We have also validated our proposed results using Monte Carlo simulations.
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 transmitter and legitimate 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), the average secrecy capacity (ASC), and the asymptotic of the ASC (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.
This work is concerned with the secrecy performance of a free-space optical (FSO) communication system over Fisher-SnedecorF-distribution turbulence fading channel. Considering the influence of pointing error, atmospheric turbulence and different detection technique (i.e., the intensity modulation with direct detection and heterodyne detection), we derive the exact closed-form expressions for the average secrecy capacity (ASC), the secrecy outage probability (SOP) and the strictly positive secrecy capacity (SPSC) in terms of Meijer’s G-function. Furthermore, the asymptotic expression for SOP is analyzed as the electrical signal-to-noise ratio approaches infinity. Monte Carlo simulations are provided to validate analytical results.
With the deployment of hybrid RF-FSO networks, there exists the potential to contribute significantly to the evolving landscape of 6G communication, as it effectively addresses challenges pertaining to connectivity, capacity, and security. In this paper, we study the secrecy performance of hybrid radio frequency (RF) - free space optical (FSO) systems in the presence of an eavesdropper. To improve the reliability of the source-destination transmission process, we consider a source that can transmit data via both RF and FSO links, simultaneously. Specifically, the RF links are exposed to generalized α – μ fading channels, while the FSO link is subject to Málaga distributions. Therefore, we deduce the novel analytical expression of secrecy outage probability and verify the results with the Monte Carlo simulations. The outcomes underscore the pronounced impact of fading parameters, receiver detection techniques, pointing errors, and atmospheric turbulence on security performance.
In this paper, we study the secrecy performance of a mixed radio frequency-free space optical (RF-FSO) transmission systems. All RF links experience Nakagami-m fading and the FSO link experiences the Gamma-Gamma fading. The effect of pointing error and two types of detection techniques (i.e., heterodyne detection and intensity modulation with direct detection) are considered. We derive closed-form expressions for lower bound of the secrecy outage probability (SOP) and exact average secrecy capacity (ASC). Furthermore, by utilizing the expansion of Meijer's G-function, asymptotic results for SOP and ASC are derived when the electrical signal-to-noise ratio of the FSO link tends to infinity. Numerical and Monte Carlo simulation results are provided to verify the accuracy of our proposed results.
In this article, we study the physical layer security of free-space optical (FSO) communications under different eavesdropping scenarios. More specifically, the secrecy performance of FSO communication employing intensity modulation/direct detection detection is analyzed for the well-established Málaga channels. Three different realistic scenarios of eavesdropping are considered by assuming different placement locations for the eavesdropper in the paper. Novel expressions for the average secrecy capacity (ASC) and secrecy outage probability (SOP) are derived for the considered scenarios, and useful insights are also provided through asymptotic analysis. The results show: (1) When the eavesdropper is placed near the transmitter, atmospheric condition imposes a less significant impact on secrecy performance; (2) Certain level of correlation can potentially enhance the secrecy performance for FSO communications; (3) The correlation imposes opposite impacts on the ASC and SOP of FSO communications; and the secrecy performance metrics exhibit a non-monotonic impact with the increase of correlation; (5) When the correlation of the FSO links is too small or too large (i.e., the correlation parameter around 0 or 1), the correlation plays a more significant impact on secrecy performance; and (6) The asymptotic slope of the SOP is 0.5 for all eavesdropping scenarios under practical FSO channels.
In this paper, the secrecy performance of a mixed radio frequency-free space optical (RF-FSO) communication system that consists of a source (S), a relay (R), a destination (D), and an eavesdropper (E), is studied. In this system, it is assumed that the E can overhear the free space optical (FSO) link between R and D as it is close to D. It is further assumed that the radio frequency (RF) and FSO links experience Rayleigh and Gamma-Gamma fading, respectively. Considering atmospheric turbulence, pointing errors, two types of detection techniques, and decode-and-forward scheme, the closed-form expressions for the lower bound of secrecy outage probability and the probability of strictly positive secrecy capacity are derived. Monte Carlo simulation results are also presented to validate the accuracy of the derivations.