This paper focuses on the impact of opportunistic scheduling schemes on the secrecy performance of a multiuser free-space optical network (MU-FSON). Considering a presence of a single passive eavesdropper, the best user with the highest signal-to-noise value is selected by the legitimate receiver among multiple users to communicate over an FSO link. The FSO links are assumed to follow the Málaga-M fading model with pointing errors. Initially, we derive a theoretical model of an MU-FSON considering the best user selection scheme. Then, the system outage probability and the system intercept probability are derived as the secrecy performance metrics of the considered MU-FSON. Our derived analytical expressions present an efficient tool to investigate the impact of some system and channel parameters on the secrecy performance, namely the number of users in the legal transmission process, atmospheric turbulence severity, and pointing errors of the FSO link. Numerical results are presented to validate the derived expressions and the accuracy of the obtained numerical results is confirmed by Monte-Carlo simulations.
This paper focuses on the impact of opportunistic scheduling schemes on the secrecy performance of a multiuser free-space optical network (MU-FSON). Considering a presence of a single passive eavesdropper, the best user with the highest signal-to-noise value is selected by the legitimate receiver among multiple users to communicate over an FSO link. The FSO links are assumed to follow the Málaga-M fading model with pointing errors. Initially, we derive a theoretical model of an MU-FSON considering the best user selection scheme. Then, the system outage probability and the system intercept probability are derived as the secrecy performance metrics of the considered MU-FSON. Our derived analytical expressions present an efficient tool to investigate the impact of some system and channel parameters on the secrecy performance, namely the number of users in the legal transmission process, atmospheric turbulence severity, and pointing errors of the FSO link. Numerical results are presented to validate the derived expressions and the accuracy of the obtained numerical results is confirmed by Monte-Carlo simulations.
This research paper investigates the security and reliability aspects of a multiuser free space optical (MU-FSO) system when exposed to eavesdropper attacks. The system experiences atmospheric turbulence, specifically generalized Fisher-Snedecor F turbulence, which leads to significant signal fading. To enhance the security and reliability of the MU-FSO system, the study employs three scheduling schemes: optimal scheduling (OS), round-robin scheduling (RS), and cumulative distribution function scheduling (CS). The paper derives precise expressions for the intercept probability (IP) and outage probability (OP) of the MU-FSO system to compare the performance of these opportunistic scheduling schemes considering the impact of atmospheric turbulence and path loss. Additionally, the paper presents simplified expressions for the asymptotic behavior of IP and OP with acceptable accuracy. Numerical results demonstrate how the performance of the MU-FSO system in terms of secrecy and reliability is influenced by factors such as the conditions of the main and wiretap channels, distances between legitimate users, the number of active users, and the power levels of the legitimate and eavesdropping links. Monte Carlo simulations are used to verify the correctness of the numerical results.
The security-reliability tradeoff (SRT) in free-space optical (FSO) communications is the most critical property to highlight, especially with respect to the development of wireless optical communications. In this paper, opportunistic scheduling selection techniques are used to improve the SRT of multiuser FSO systems under the combined influence of atmospheric turbulence with Fisher-SnedecorFdistribution, generalized pointing error, and path losses due to foggy weather. Due to the broadcast nature of wireless optical propagation, the optical transmission from the transmitting users to the legitimate receiver can be easily intercepted by eavesdroppers. Therefore, an optimal user scheduling (OUS) scheme is proposed in this work to protect the legitimate wireless transmission from eavesdroppers, where a user with the highest secrecy capacity is scheduled to transmit his confidential information to the receiver. Closed-form expressions for the outage probability, interception probability, and SRT are derived for the conventional round-robin scheduling (RRS) and the proposed OUS. In addition, an asymptotic analysis for the outage probability, interception probability, and SRT is performed to provide insight into the impact of user scheduling on the system performance. We also propose the use of “friendly jamming” techniques, where the user with the lowest secrecy capacity is selected by the authorized receiver to jam the existing interceptor. Finally, another SRT is formulated to determine the impact of a friendly jammer on the secrecy performance of the system. The results show that the proposed OUS outperforms the RRS in terms of intercept probability and SRT performance. The obtained exact and asymptotic results are validated by Monte-Carlo simulations.
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.
In this paper, the impact of radio frequency (RF) co-channel interference (CCI) on the performance of multiuser (MU) mixed RF/free space optical (FSO) relay network with opportunistic user scheduling is studied. In the considered system, a user is opportunistically selected to communicate with a single destination through an amplify-and-forward (AF) relay in the presence of a single passive eavesdropper. The RF/FSO channel models are assumed to follow Rayleigh/Gamma-Gamma fading models, respectively with pointing errors and identical RF CCI signals. Exact closed-form expression for the system outage probability is derived. Then, an asymptotic expression for the outage probability is obtained at the high signal-to-interference-plus-noise ratio (SINR) regime. The asymptotic results are used to formulate a power allocation problem to obtain optimal RF transmission power. Then, the secrecy performance is studied in the presence of CCI at both the authorized relay and eavesdropper by obtaining exact and asymptotic closed-form expressions for the intercept probability. The derived analytical formulas herein are supported by numerical and simulation results to clarify the main contributions of the work.
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, 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.