Secure Outage Probability Research Articles

Enhancing security in multicasting through correlated Nakagami-[formula omitted] fading channels with opportunistic relaying

We consider a confidential wireless multicasting scenario in which a base station sends a common stream of information to a group of U users via K relays. V eavesdroppers are trying to decode that confidential information. We are interested to protect the decoding of that information and to see, how the opportunistic relaying can be used to enhance the level of security reducing the effect of correlations. We derive the closed-form analytical expressions for the probability of non-zero secrecy multicast capacity and the secure outage probability for multicasting in terms of the best relaying, and the correlation coefficients of constant, exponential and arbitrary correlations. Our results show that all the correlations are enemy of wireless security in multicasting and the impact of constant correlation is more significant than the exponential and arbitrary correlations. Although the performance of confidential wireless multicasting scenario decreases with the number of multicast users and due to the effect of correlations but this performance can be improved to an original one using the well known opportunistic relaying technique instead of increasing transmit signal power. Since all the relays compete to be the best relay, hence the trade off between the number of relays and multicast users has been established to maintain the acceptable security level reducing the effect of correlations. Finally, analytical results are verified via Monte-Carlo simulation.

Joint transmitter and PS factor optimal design for secure transmission in MIMO full‐duplex relay network powered by SWIPT with perfect and imperfect channel state information

The joint transmitter and PS factor optimal design scheme for secure transmission in multiple-input multiple-output (MIMO) full-duplex relay network powered by simultaneous wireless information and power transfer (SWIPT) is studied. An optimisation problem is presented, aimed at maximising the system security capacity by jointly optimising transmitter and PS factor while satisfying the energy harvest constraint in both perfect and imperfect channel state information (CSI). In perfect CSI case, the optimisation function is formulated with energy harvest constraint, and semidefinite relaxation (SDR) is introduced to solve the non-convex optimisation problem. In imperfect CSI case, it is assumed that only the first and second order statistics of the eavesdropper's channels are available, but the specific distribution is unknown. In this case, the security capacity of the system is maximised while satisfying the security outage probability and energy harvest constraint. The SDR solution based on equivalent conic reformulation is proposed. And the simulation results demonstrate the effectiveness of the optimal designs in both CSI cases.

Physical layer security in shotgun cellular systems over correlated/independent shadow fading channels

The shotgun cellular systems (SCSs) (modeling, generally, a dense cellular or wireless data network deployment and non-ideal regular hexagonal grid with site-acquisition difficulties, variable traffic load) are wireless communication systems with randomly placed base stations (BSs) over the entire plane according to a stochastic (e.g., Poisson) point process in n dimensions (n = 1, 2, and 3). Due to the good performance and the importance of the SCSs in today’s communications, the physical layer security of these systems is practically of importance, specifically, in more realistic channel propagation models. In this paper, by assuming that the channel coefficients are known at the receiver, we analyze the performance of the physical layer security for the classic Wyner’s three-node model in the SCSs over correlated/independent log-normal shadow fading channels. For this purpose, first, we calculate the signal-to-interference-plus-noise ratio (SINR) performance at a mobile station (MS) in an SCS. Then, the average secrecy capacity (ASC), the probability of non-zero secrecy capacity (PNSC), the secure outage probability (SOP), and the lower bound of SOP (LSOP) are obtained, and also, their approximated closed-form expressions are derived. Finally, analytical results are validated numerically.

Achievable Physical-Layer Security Over Composite Fading Channels

We investigate the physical layer security limits of Wyner's wiretap model over Fisher-Snedecor .T composite fading channels. .T fading conditions have been recently shown to provide an accurate characterization of multipath fading and shadowing effects in emerging wireless transmission scenarios such as body centric, cellular and vehicular communications. To this end, we utilize a redefined analytic expression for the Fisher-Snedecor .T distribution in order to ensure unconstrained validity and reliability when used in the analysis of various performance metrics of interest. In this context, we assume that the main channel (i.e., between the source and the legitimate destination) and the eavesdropper's channel (i.e., between the source and the illegitimate destination) undergo independent quasi-static Fisher-Snedecor .T composite fading. Novel exact analytic expressions are then derived for the corresponding average secrecy capacity (ASC), secure outage probability (SOP) and probability of strictly positive secrecy capacity (SPSC) along with their insightful asymptotic representations. In addition, analytical expressions for the ASC, SOP and SPSC over mixed fading channels such as Nakagami-m/Nakagami-m, Nakagami-m/Fisher-Snedecor .T and Fisher-Snedecor .T/Nakagami-m are derived. The new formulations are validated through comparisons with Monte-Carlo simulations and analyzed to gain useful insights into the impact of the fading parameters on the achievable accuracy and the overall system performance.

Secrecy Performance Analysis of Mixed Hyper-Gamma and Gamma-Gamma Cooperative Relaying System

In this paper, we investigate a secure dual-hop radio frequency-free space optical (RF-FSO) mixed variable gain relaying framework in the presence of a single eavesdropper. The RF and FSO links are modeled with hyper Gamma (HG) and Gamma-Gamma (ΓΓ) fading channels, respectively. We assume that the eavesdropper utilizes another HG fading channel to wiretap the transmitted confidential data from the RF link. Our key concern is to defend this information against passive eavesdropping. We carry out the secrecy measurements by deriving closed-form mathematical expressions of average secrecy capacity (ASC), secure outage probability (SOP), and strictly positive secrecy capacity (SPSC), all in terms of Meijer's G function. Capitalizing on the derived expressions, we analyze the impacts of atmospheric turbulence and pointing errors on the secrecy capacity and outage performance of the proposed scenario. For gaining more insights, we also analyze the asymptotic outage behaviour for high signal-to-noise ratio. Two detection techniques i.e. heterodyne (HD) and the intensity modulation with direct detection (IM/DD) are taken into consideration and our results demonstrate that HD technique notably outperforms the IM/DD scheme. The supremacy and novelty of the model is demonstrated via utilizing generic properties of the HG fading channel. Finally, we provide a justification of the derived expressions via Monte-Carlo simulations.

Evaluating secrecy performance of cooperative NOMA networks under existence of relay link and direct link

SummaryThe secrecy performance of a nonorthogonal multiple access (NOMA) system is examined in this study by employment of a dual‐hop decode‐and‐forward (DF) relay under existence of eavesdropper. Due to the fact that the relay is trusted or untrusted device and thus eavesdropper may wiretap information from the base station or the relay. In this regard, three scenarios related to trusted and untrusted relays are proposed, with different assumptions on the information overhearing ability of the eavesdropper; ie, the first scenario is that an eavesdropper overhears signal from the relay while the BS is overheard by eavesdropper in the second scenarios. More specifically, we derive closed‐form expressions for the secure probability metrics when the direct and relay links experience independent Rayleigh fading. There metrics include strictly positive secrecy capacity (SPSC) and the secure outage probability (SOP). Furthermore, secure performance of traditional orthogonal multiple access (OMA) is also provided as further comparison with NOMA counterpart. We analyze the influence of main coefficients such as the target rates and the transmit SNR factors on the secrecy performance. Our results specify that for reasonable selection of such parameters, secrecy performance can be enhanced remarkably. Numerical results are delivered to corroborate the derived results.

Exact closed‐form capacity and outage probability of physical layer security in shadowed fading channels

In this study, the secrecy performance of physical layer when both the main and wiretap channels undergo κ − μ shadowed fading conditions is analysed. In particular, the average secrecy capacity, secure outage probability (SOP), the lower bound of SOP (SOP L ), and the probability of strictly positive secrecy capacity are derived by using the classic Wyner's wiretap model. Two different scenarios for the fading parameters, namely, μ and m, which represent the real extension of the number of the multipath clusters and the shadowing index, respectively, have been studied. These parameters are chosen first as arbitrary numbers, thus the performance metrics are given in exact closed-form in terms of the extended generalised bivariate Fox's H-function that has been widely implemented in the open literature using various software packages. In the second scenario, both the fading parameters are assumed to be integer numbers to obtain the derived results in simple exact closed-form mathematically tractable expressions in terms of some analytic functions. The numerical results of this analysis are verified via the Monte Carlo simulations.

Secrecy Outage Analysis for Cooperative NOMA Systems With Relay Selection Schemes

This paper considers the secrecy outage performance of a multiple-relay assisted non-orthogonal multiple access (NOMA) network over Nakagami-m fading channels. Two time slots are utilized to transmit signals from the base station to destination. At the first time slot, the base station broadcasts the superposition signal of the two users to all decode-and-forward relays by message mapping strategy. Subsequently, the selected relay transmits superposition signal to the two users via power-domain NOMA technology. Three relay selection schemes, i.e., optimal single relay selection (OSRS) scheme, two-step single relay selection (TSRS) scheme, and optimal dual relay selection (ODRS) scheme are proposed and the secrecy outage performance is analyzed. As a benchmark, we also examine the secrecy outage performance of the NOMA systems with traditional multiple relay forwarding (TMRF) scheme in which all the relay that successfully decode signals from the source forward signals to the NOMA users with equal power. Considering the correlation between the secrecy capacity of two users and different secrecy requirement for two NOMA users, the analytical expressions for the security outage probability (SOP) of the proposed OSRS, TSRS, and ODRS schemes along with the TMRF scheme are derived and validated via simulations. To get more insights, we also derive the analytical expressions for the asymptotic SOP for all the schemes with fixed and dynamic power allocations. Furthermore, the secrecy diversity order (SDO) and secrecy array gain of cooperative NOMA systems are obtained. The results demonstrate that our proposed schemes can significantly enhance the secrecy performance compared to the TMRF scheme and that all the schemes with fixed power allocation obtain zero SDO and the OSRS scheme with dynamic power allocation obtains the same SDO as TMRF.

Performance analysis of physical layer security over Weibull/lognormal composite fading channel with MRC reception

With the advent of denser network and internet of things (IoT) applications for fifth generation (5G) communication, there is a need to understand and define the security limitations. This paper proposes closed-form expressions for different physical layer security (PLS) metrics for millimeter wave (mmWave) communication for the 5G systems and IoT applications. The information-theoretic formulation is considered in which licit users can impart their data over a quasi-static channel and eavesdroppers perceive their communication through another quasi-static channel, where the channel is represented as Weibull/lognormal (WL) composite fading channel in mmWave. To this end, the closed-form expressions for the probability of density function (PDF) and cumulative distribution function (CDF) are firstly derived. This set of results are then used to derive the closed-form expressions for the lower bound of secure outage probability (SOPL) and strictly positive secrecy capacity (SPSC) with maximal ratio combining (MRC) reception. In addition, average secrecy capacity (ASC) is also analyzed and expressed in closed-form. Furthermore, the derivation is extended for the performance metrics for the two eavesdroppers case to provide perspective for more complex yet practical situation.

Secrecy performance of massive MIMO relay‐aided downlink with multiuser transmission

In this study, the authors study secure multiuser transmission in a massive multiple-input multiple-output (MIMO) relaying system, where a base station sends its messages to multiusers via an amplify-and-forward relay station. Beamforming matrices of maximum ratio combining/maximum ratio transmission (MRC/MRT) and zero-forcing reception/zero-forcing transmission (ZFR/ZFT) at relay are considered. The authors derive exact and asymptotic expressions for user rate and outage secrecy rate for a predetermined secure outage probability of eavesdropper links with channel state information imperfection. They have shown that ZFR/ZFT is a better choice than MRC/MRT from the perspectives of secrecy performance. Furthermore, the asymptotic analysis is proposed to show that almost the eavesdropper rates in all cases are degraded as a number of relay antennas goes to infinity, and simultaneously the transmit power at the base station and the relay can be scaled down significantly. Finally, numerical results provide more insightful validity of the proposed analysis.

Impact of Untrusted Relay on Physical Layer Security in Non-Orthogonal Multiple Access Networks

In this study, the wireless sensor network is investigated in scenario of untrusted relay required to user at far distance. In particular, an untrusted relay assists long distance transmission in situation of non-existence of the direct link between source and destination. This paper employs non-orthogonal multiple access (NOMA) scheme to serve large number of users at different allocated power levels to adapt secure criteria. Specifically , to evaluate the security performance we first examine the secure outage probability (SOP) and then strictly positive secrecy capacity (SPSC) is studied. To further characterize the trade-off between system security and other controlling coefficients, we then investigate the impacts of power allocation factors and power levels of the eavesdropper. In order to find tractable expressions to provide additional insights in term of the performance evaluation, the asymptotic expressions regarding both SOP and SPSC are performed in high signal-to-noise ratio (SNR) region. In addition, secure performance of considered NOMA network is compared in two modes related to untrusted relay, including Amplify-and-Forward and Decode-and-Forward mode. Finally, simulation results are presented to corroborate the proposed methodology.

NOMA-Assisted Multiple Access Scheme for IoT Deployment: Relay Selection Model and Secrecy Performance Improvement.

In this paper, an Internet-of-Things (IoT) system containing a relay selection is studied as employing an emerging multiple access scheme, namely non-orthogonal multiple access (NOMA). This paper proposes a new scheme to consider secure performance, to be called relay selection NOMA (RS-NOMA). In particular, we consider metrics to evaluate secure performance in such an RS-NOMA system where a base station (master node in IoT) sends confidential messages to two main sensors (so-called NOMA users) under the influence of an external eavesdropper. In the proposed IoT scheme, both two NOMA sensors and an illegal sensor are served with different levels of allocated power at the base station. It is noticed that such RS-NOMA operates in two hop transmission of the relaying system. We formulate the closed-form expressions of secure outage probability (SOP) and the strictly positive secure capacity (SPSC) to examine the secrecy performance under controlling setting parameters such as transmit signal-to-noise ratio (SNR), the number of selected relays, channel gains, and threshold rates. The different performance is illustrated as performing comparisons between NOMA and orthogonal multiple access (OMA). Finally, the advantage of NOMA in secure performance over orthogonal multiple access (OMA) is confirmed both analytically and numerically.

Secrecy Performance Analysis of SIMO Systems Over Correlated $\kappa$ –$\mu$ Shadowed Fading Channels

In this paper, the secrecy performance of single-input–multiple-output systems over correlated $\kappa $ - $\mu $ shadowed fading channels is investigated. In particular, based on the classic Wyner’s wiretap model, we derive analytical expressions for secure outage probability (SOP) and the probability of strictly positive secrecy capacity (SPSC) over correlated $\kappa $ - $\mu $ shadowed fading channels. In order to further study the impact of channel parameters on the secrecy performance, novel SOP and the probability of SPSC over independent and identically distributed $\kappa $ - $\mu $ shadowed fading channels are also obtained. In addition, we discuss the asymptotic expressions of the SOP and the SPSC. The match between the analytical results and simulations is excellent for all parameters under considerations. It is interesting to find that the results show that when the signal-to-noise ratio of the main channel is lower than that of the eavesdropping channel, the larger value of correlation coefficient is helpful to improve the secrecy performance and vice versa.

Physical Layer Security Performance of Wireless Mobile Sensor Networks in Smart City

In smart cities, the ubiquitous network connections and high data rate services are provided to afford effective service of real-time monitoring and responses. With the development of the 5G mobile communication technology, the wireless sensor mobile communication networks in the smart city have become a hot issue for academic researches. Due to the openness of wireless channels, the physical layer security of the wireless mobile sensor mobile communication networks in smart city encounters severe challenges. In this paper, based on Wyner’s wiretap model, the secrecy performance of the wireless mobile sensor communication networks over 2-Nakagami fading channels is investigated. We derive the exact secure outage probability (SOP) and the probability of strictly positive secrecy capacity expressions for two transmit antenna selection (TAS) schemes. The exact closed-form expressions for the lower bound on the SOP are also derived using the optimal TAS scheme. Then, the system secrecy performance is verified and analyzed by Monte Carlo simulations under different conditions. The simulation results show that the analytical results match perfectly with the Monte Carlo simulation results. Increasing the number of transmit antennas can improve secrecy performance.

Performance Analysis of Physical-Layer Security Over Fluctuating Beckmann Fading Channels

In this paper, we analyse the performance of physical layer security over Fluctuating Beckmann (FB) fading channel, which is an extended model of both the κ - μ shadowed and the classical Beckmann distributions. Specifically, the average secrecy capacity (ASC), secure outage probability (SOP), the lower bound of SOP (SOPL), and the probability of strictly positive secrecy capacity (SPSC) are derived using two different values of the fading parameters, namely, m and μ which represent the multipath and shadowing severity impacts, respectively. Firstly, when the fading parameters are arbitrary values, the performance metrics are derived in exact expressions in terms of the extended generalised bivariate Fox's H-function (EGBFHF) that has been widely implemented in the open literature. In the second case, to obtain simple mathematically tractable expressions in terms of analytic functions as well as to gain more insight on the behaviour of the physical layer security over Fluctuating Beckmann fading channel models, m and μ are assumed to be integer and even numbers, respectively. In addition, the asymptotic behaviour for all the studied performance metrics has been provided. The numerical results of this analysis are verified via Monte Carlo simulations.

Enhancing Security in Cognitive Radio Multicast Networks Using Interference Power

In this paper, security issue in multiple input multiple output (MIMO) multicasting system has been analyzed in the presence of a group of eavesdroppers in cognitive radio networks (CRNs). Primary base station (PBS) and secondary base station (SBS) communicate with multiple primary and secondary receivers, respectively via a precoding relay having multiple antennas. At first, considering interference the secrecy multicast capacity at the primary receivers (PRs) and the secondary receivers (SRs) has been calculated and investigated the impact of interferences on it. Then, the zero-forcing (ZF) precoding technique at the relay has been employed which enhances the secrecy multicast capacity at the PRs and SRs by zeroing the impact of interference on each other. Secondly, the existing constructive interference energy of the communication medium employing selective precoding (SP) technique at the relay has been used to improve the secrecy multicast capacity of the PRs and SRs. Finally, phase alignment precoding (PAP) technique at the relay has been introduced which uses the destructive part of interference for further increase in the secrecy multicast capacity at the PRs and SRs. It is observed that among the three precoding techniques, the best performance is achieved by using the PAP at the relay in terms of secrecy multicast capacity and secure outage probability analysis. This is due to the fact that PAP technique at the relay not only uses the constructive interference part but also it rotates the destructive interference part in such a way that the resulting interference is always instantaneously constructive. So using these precoding relays interference power can be used to enhance system performance without increasing base station power.

Secure Relay Selection for Two Way Amplify-and-Forward Untrusted Relaying Networks

Relay assisted communication helps to extend the transmission coverage area. In more realistic scenarios, the available relays are untrusted, which try to decode the confidential signals during their main relaying function. Thus, these untrusted relays are regarded as potential eavesdroppers, and the confidential signals are vulnerable. A positive secrecy rate can be achieved at the physical layer without any cryptography, in particular, the mutual interference achieved from two-way relaying network can be used to secure the confidential signals against eavesdroppers attack. In this paper, the relay selection of two-way untrusted relays network is presented, and a directed beamforming is aligned to zero force the transmission at all other non-selected relays. Particularly, we propose a selection scheme based on max–min criterion, which requires an exhaustive search. Then, the lower bound (LB) of the secrecy rate is introduced to minimize the complexity of the selection criterion. The closed forms of the secure outage probability (SOP) for the max–min LB scheme is formulated and compared with other schemes. The simulations results validate the proposed analytical forms, and the performance of max–min LB scheme appears to be quite close to that of the max–min scheme with limited complexity.

Physical Layer Security For Dual-Hop VLC/RF Communication Systems

In this letter, we investigate the physical layer security of a mixed visible light communication (VLC)/radio-frequency (RF) system. More specifically, the relay can extract the direct current component and collect energy from the optical signal in the VLC link and then use this collected energy to retransmit data though the RF link. With this setup, the exact performance expressions for secure outage probability and average secrecy capacity are derived in closed form. We also provide asymptotic results to investigate the effect of different system parameters on the system performance. Finally, we present numerical results to illustrate our analytical result.

Secure wireless multicasting through AF-cooperative networks with best-relay selection over generalized fading channels

We consider a secure wireless multicasting scenario over Generalized $$\kappa -\mu$$ fading channels via multiple amplify-and-forward cooperative relays. In the first hop, a source S transmits a common stream of information to a group of K relays. In the second hop, the best relay which has the highest signal-to-noise ratio, forwards the amplified version of information to a group of M destination users in the presence of multiple eavesdroppers. We assume that there is no direct link between source and destination users as well as eavesdroppers. Destinations and eavesdroppers are communicating with the source via relays only. The key contribution of this paper is to enhance the security of wireless multicasting using the additional diversity provided by the best relay of K relays. In order to investigate the performance of the proposed model, we derive the analytical expressions for the probability of non-zero secrecy multicast capacity and the secure outage probability in terms of the number of relays, destination users and eavesdroppers. Finally, the analytical expressions are verified via Monte Carlo simulation.

Selection combining hybrid FSO/RF systems over generalized induced-fading channels

Abstract A hybrid free space optical (FSO)/millimeter-wave radio frequency (mmWave RF) technology is a promising scheme to improve an optical link reliability and availability. In this paper, the performance of a selection combining hybrid FSO/RF system is investigated. The FSO link and mmWave RF link are modeled by the generalized Malaga ( M ) and η − μ distributions respectively. The effect of pointing errors as a result of misalignment between transmitter and receiver in the FSO link is also included. At the receiver, selection combining is considered to detect the link with the highest electrical signal-to-noise ratio (SNR). Moreover, closed-form expressions for the system performance in terms of the outage probability at high SNR and average bit error rate (ABER) for different binary modulation schemes are then derived for the FSO link, RF link and hybrid FSO/FSO systems. In addition, special cases in terms of Gamma–Gamma (GG), Nakagami-m fading distribution are obtained from the derived expression for the hybrid system. The security outage probability performance for the hybrid system is also determined by assuming that the channel of an Eavesdropper to the RF link undergoes Nakagami-m fading distribution. The results presented show that hybrid system can overcome the weakness of FSO links which are susceptible to atmospheric turbulence and pointing errors. Finally, the simulation results are presented to prove the accuracy of the derived expressions.