In this paper, we investigate the physical layer security for an asymmetric dual-hop radio frequency-free space optical (RF-FSO) communication system, in which a source transmits information to a multi-aperture destination (D) through a best relay under the wiretapping of a multi-aperture eavesdropper (E). The best relay is selected by a partial relay selection scheme in terms of maximum instantaneous channel gain for the RF link. Moreover, equal gain combining scheme is also used to process the multiple copies of receiving signal at D and E. Assuming all the RF channels are subject to independent and identical distributed (i.i.d.) Nakagami-m fading and all the FSO channels are modeled by i.i.d. Gamma-Gamma process, the secrecy performance in terms of secrecy outage probability and the probability of strictly positive secrecy capacity are studied, and the accuracy of the analytical results is verified by Monte-Carlo simulations.
In this paper, we investigate the physical layer security for an asymmetric dual-hop radio frequency-free space optical (RF-FSO) communication system, in which a source transmits information to a multi-aperture destination (D) through a best relay under the wiretapping of a multi-aperture eavesdropper (E). The best relay is selected by a partial relay selection scheme in terms of maximum instantaneous channel gain for the RF link. Moreover, equal gain combining scheme is also used to process the multiple copies of receiving signal at D and E. Assuming all the RF channels are subject to independent and identical distributed (i.i.d.) Nakagami-m fading and all the FSO channels are modeled by i.i.d. Gamma-Gamma process, the secrecy performance in terms of secrecy outage probability and the probability of strictly positive secrecy capacity are studied, and the accuracy of the analytical results is verified by Monte-Carlo simulations.
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.
We investigate the physical-layer security performance for a wireless-powered relaying mixed free-space optical-radio frequency (FSO-RF) system. In this system, a source transmits optical information to a relay (R), which decodes the received signal with a decode-and-forward protocol, converts it into an RF signal, and forwards it to a destination in the presence of an eavesdropper. Furthermore, we also assume that R has no extra power supply, and it only relies on harvesting energy from a power beacon to forward the information. Assuming that the FSO and all of the RF channels experience gamma-gamma and Rayleigh fading, the closed-form analytical expressions for secrecy outage probability and the probability of strictly positive secrecy capacity are derived. In addition, the effects of atmospheric turbulence, pointing errors, and detection techniques on the system performance are analyzed. Finally, we perform Monte Carlo simulations to verify the accuracy of the derived expressions.
In this paper, we study the secrecy performance of an energy-harvested relaying assisted free space optical-radio frequency (FSO-RF) network. In particular, a single-beam source sends an optical signal to a multi-aperture relay over an FSO channel, and then the relay converts it into an RF signal and adopts a decode-and-forward protocol to forward it to a multi-antenna destination under the wiretapping of a multi-antenna eavesdropper. We assume that the relay is power constrained, and it requires to harvest energy from a power beacon to assist the information transmission. It is also assumed that the FSO link and all RF links are subject to gamma-gamma fading with atmospheric turbulence and Rayleigh fading, respectively. Analytical expressions for secrecy outage probability (SOP) and the probability of strictly positive secrecy capacity are derived. In addition, the asymptotic expression for SOP is obtained to present insight into secrecy performance at high signal-to-noise ratio regimes. Finally, Monte Carlo simulations verify the correctness of the theoretical derivations.
In this paper, the secrecy performance from the perspective of secrecy outage probability(SOP) for a free space optical-radio frequency (FSO-RF) network with an amplify-and-forward (AF) relaying under the wiretapping of an eavesdropper is investigated. Specifically, a superimposed signal of two users is first transmitted from a source (S) to a relay (R) over an FSO link, and then converted by R into an electrical one and broadcasted to their corresponding users over the RF links, while an eavesdropper is overhearing this transmission. In addition, the information transmission in both hops is incorporated with a non-orthogonal multiple access technique. Assuming the FSO and the RF links undergo Gamma-Gamma fading and Nakagami-mfading respectively, the analytical expression for SOP is first obtained and then verified with simulation results.
In this paper, the physical layer security (PLS) analysis for a decode-and-forward (DF) protocol based multi-hop hybrid radio frequency (RF)/ free space optics (FSO) is presented. Herein, two different scenarios are considered for detecting the secured information at the destination. In the first scenario, at each hop, the received signals with higher secrecy capacity are selected. However, in the second scenario, the RF and FSO signals are simply decoded and forwarded to the next hop and selection is done at the last hop only. Each node in the system is connected to its subsequent node through parallel RF and FSO links. The FSO links and RF links are characterized by Málaga (M) and Nakagami-mcomposite distributions respectively. For both scenarios, the secrecy outage probability (SOP), strictly positive secrecy capacity (SPSC), intercept probability (IP), and effective secrecy throughput (EST) are obtained as performance metrics. These performance metrics are obtained by considering pointing error, different optical signal detection methods, turbulence effect, and the RF link fading parameter (m). Using the results, the security and reliability trade-off analysis is discussed for two scenarios. In addition, the asymptotic results are also obtained to study the system in depth. Further, the secrecy diversity order (SDO) and secrecy coding gain (SCG) are obtained to analyse the system in depth. Finally, Monte-Carlo Simulation is performed to verify the obtained results. The results manifest that the scenario with selection at each hop provides better secrecy performance than the scenario with selection at the last hop.
In this paper, we investigate the secrecy performance of multiuser (MU) single-input multiple-output (SIMO) mixed radio frequency (RF)/free space optical (FSO) relay network with opportunistic user scheduling and multiple eavesdropping attacks. The considered system includes multiple users, one amplify-and-froward (AF) relay, one destination and multiple eavesdroppers. The users are connected with a multi-antenna relay through RF links and the relay is connected with the destination through an FSO link. Maximal ratio combining (MRC) scheme is used at the relay node to combine the received signals at its different antennas. The RF/FSO channels are assumed to follow Nakagami-m/Gamma-Gamma fading models with considering the effect of pointing errors. In particular, we derive closed- form expressions for the exact and asymptotic outage probabilities. The asymptotic outage results are then used to obtain the optimal RF transmission power based on the dominant link between the RF and FSO links. Then, the considered system secrecy performance is investigated in the presence of multi- eavesdroppers where exact closed-form expression for the intercept probability is derived. Finally, a cooperative jamming model is proposed along with power allocation to enhance the system secrecy performance. Monte-Carlo simulations are provided to validate the achieved exact and asymptotic results.