Secrecy Outage Probability Research Articles

Secrecy Performance for RIS-Based Integrated Satellite Vehicle Networks With a UAV Relay and MRC Eavesdropping

This work investigates the secrecy issues for the secrecy reconfigurable intelligent surface-based integrated satellite unmanned aerial vehicle (UAV) relay networks with multiple vehicle eavesdroppers. Particularly, the maximal ratio combining (MRC) eavesdropping is utilized to overhear the legitimate signal information. The UAV is applied to forward the legitimate signal to the destination user. Reconfigurable intelligent surface is applied to ensure the transmission. Relied on the proposed secrecy system model and MRC eavesdropping scheme, this paper gets the detailed investigations for the secrecy outage probability (SOP) through the whole signal-to-noise ratios (SNRs) to valuate the effects of important parameters on the SOP. Moreover, to achieve the further impacts of main parameters on the SOP at high SNRs, the approximate analysis for the SOP is also gotten together with the secrecy diversity order (SDO) and secrecy coding gain (SCG). At last, several typical Monte Carlo (MC) results are obtained to present the rightness of obtained theoretical analysis.

The Generalized-Fisher composite fading model for the next generation of mobile communication systems

The new generation of communication systems is moving towards using a millimeter-wave spectrum. Since the shadowing effects are undeniable in this type of propagation, the proposed Generalized Fisher (GF) distribution can be useful in modeling shadowed fading channels, considering the non-linearity and the multi-cluster nature of the diffusion medium. After introducing the model, its main statistics, including Probability Density Function (PDF), Cumulative Distribution Function (CDF), Moment Generating Function (MGF), and the distribution of the sum of an arbitrary number of independent and non-identically distributed (i.n.i.d.) random variables with GF distribution are calculated. Subsequently, some wireless communication application criteria such as ergodic and outage capacities, are computed. Finally, considering the classic Wyner's wiretap model and passive eavesdropping scenario, specific security criteria, such as the probability of non-zero secrecy capacity and secrecy outage probability, are also determined. These expressions are measured in terms of either univariate or multivariate Fox's H-function.

Outage Analysis of Rate Splitting Networks With an Untrusted User

Rate splitting (RS) can significantly improve the spectrum efficiency and degrees of freedom of multi-access transmissions. However, due to the characteristics of RS decoding, the secure transmission remains a challenge especially when there is an untrusted near user. Thus, two RS schemes are proposed with different successive interference cancellation (SIC) layers. For both schemes, the users first decode the common stream. In the one-layer-SIC scheme, the users then decode their own private streams without interference via zero-forcing. For the two-layer-SIC scheme, maximum ratio transmission is adopted for the trusted far user. The users decode the private stream of the untrusted user and then decode the other. Outage probability and secrecy outage probability are analyzed based on the channel statistics and the achievable rate. Simulation results verify the theoretical results and demonstrate the advantages of two schemes in terms of the common stream transmission and the security of far user.

Minimization of Secrecy Outage Probability in Reconfigurable Intelligent Surface-Assisted MIMOME System

This article investigates physical layer security (PLS) in reconfigurable intelligent surface (RIS)-assisted multiple-input multiple-output multiple-antenna-eavesdropper (MIMOME) channels. Existing researches ignore the problem that secrecy rate can not be calculated if the eavesdropper’s instantaneous channel state information (CSI) is unknown. Furthermore, without the secrecy rate expression, beamforming and phase shifter optimization with the purpose of PLS enhancement is not available. To address these problems, we first give the expression of secrecy outage probability for any beamforming vector and phase shifter matrix as the RIS-assisted PLS metric, which is measured based on the eavesdropper’s statistical CSI. Then, with the aid of the expression, we formulate the minimization problem of secrecy outage probability that is solved via alternately optimizing beamforming vectors and phase shift matrices. In the case of single-antenna transmitter or single-antenna legitimate receiver, the proposed alternating optimization (AO) scheme can be simplified to reduce computational complexity. Finally, it is demonstrated that the secrecy outage probability is significantly reduced with the proposed methods compared to current RIS-assisted PLS systems.

Enhancing Secrecy Performance for STAR-RIS NOMA Networks

Simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) is becoming a prospective technology in realizing extremely low power transmission and seamless coverage for the sixth generation (6G) wireless communication era. Motivated by this, we study the secrecy performance of the STAR-RIS assisted non-orthogonal multiple access (NOMA) networks. To be more practical, we assume that all nodes suffer from residual hardware impairments (RHIs). To characterize the performance of the considered network, the analytical expressions of the secrecy outage probability (SOP) for NOMA users over the Nakagami- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$m$</tex-math></inline-formula> fading channels are derived. Meanwhile, the asymptotic behaviors of SOP at high signal-to-noise ratio (SNR) are also studied. The numerical results show that: 1) The existence of the RHIs reduces the secrecy performance of the network under consideration. 2) The increase in the number of configurable elements <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$K$</tex-math></inline-formula> will improve the system secrecy performance.

Integrated Satellite Multiple Two-Way Relay Networks: Secrecy Performance Under Multiple Eves and Vehicles With Non-Ideal Hardware

In this paper, we study the secrecy performance for an integrated satellite multiple two-way terrestrial relay network, where the non-ideal hardware, multiple vehicle eavesdroppers and multiple legitimate vehicle users are applied in the considered networks. To derive better secrecy performance, opportunistic terrestrial selection scheme is considered for the networks. Besides, the colluding eavesdropping scheme is also considered, where all the vehicle eaves work together to overhear the information. On these foundations, the closed-form expression for the secrecy outage probability is gotten. To obtain the further insights of system parameters and channel parameters in high signal-to-noise ratio regime, the asymptotic investigations for the secrecy outage probability is also investigated. At last, Monte Carlo results are given to show the efficiency and correctness of the analytical results.

On the Physical Layer Security Performance Over RIS-Aided Dual-Hop RF-UOWC Mixed Network

Since security has been one of the crucial issues for high-yield communications such as 5G and 6G, researchers continuously come up with newer techniques to enhance the security and performance of these progressive wireless communications. Reconfigurable intelligent surface (RIS) is one of those techniques that artificially rearrange and optimize the propagation environment of electromagnetic waves to improve both spectrum and energy efficiency of wireless networks. Besides, in underwater communication, underwater optical wireless communication (UOWC) is a better alternative/replacement for conventional acoustic and radio frequency (RF) technologies. Hence, mixed RIS-aided RF-UOWC can be treated as a promising technology for future wireless networks. This work focuses on the secrecy performance of mixed dual-hop RIS-aided RF-UOWC networks under the intercepting effort of a probable eavesdropper. The RF link operates under generalized Gamma fading distribution; likewise, the UOWC link experiences the mixture exponential generalized Gamma distribution. The secrecy analysis subsumes the derivations of closed-form expressions for average secrecy capacity, exact and lower bound of secrecy outage probability, strictly positive secrecy capacity, and effective secrecy throughput, all in terms of Meijer's <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$G$</tex-math></inline-formula> functions. Capitalizing on these derivations, the effects of heterodyne and intensity modulation/direct detection systems, underwater turbulence resulting from air bubble levels, temperature gradients, and salinity gradients, are measured. Unlike conventional models that merely deal with thermally uniform scenarios, this proposed model is likely to be unique in terms of dealing with secrecy analysis of a temperature gradient RIS-aided RF-UOWC network. Lastly, the derivations are validated via Monte-Carlo simulations.

Cooperative Secrecy Techniques for Improving Physical Layer Security in NOMA-Based PLC Networks

Power Line Communication (PLC) can achieve noticeable savings in infrastructure deployment time and cost, where it uses the existing power lines for data transmission. Non-orthogonal multiple access (NOMA), is a promising technique that can accommodate multiple users via non-orthogonal resource allocation and so, it can notably improve spectral efficiency and reduce the electromagnetic compatibility of PLC networks. Data privacy is of crucial importance in PLC design due to its broadcasting nature. Therefore, this paper presents several cooperative secrecy techniques for improving physical layer security in NOMA-based PLC networks considering two different security constraints, which are signal eavesdroppers and multiple cooperative eavesdroppers. The secrecy performance is measured in terms of two performance metrics: ergodic secrecy capacity (ESC) and secrecy outage probability (SOP). Monte Carlo simulation results validate the accuracy of the analytical model and derivations.

Wireless-powered backscatter communications for smart sustainable cities: A secrecy analysis

Due to its ability to enable self-sustainable communications, wirelessly powered backscatter communication (WP-BackCom) has been deemed a promising technology for supporting smart sustainable cities. We note that the existing works on analyzing the secrecy performance of WP-BackComs have largely ignored the spatial randomness of nodes that is used to model a large-scale network. To fill this gap, this paper evaluates the secrecy outage probability of the large-scale WP-BackComs based on a tractable framework of stochastic geometry (SG). In particular, the imperfect successive interference cancellation (SIC) at each gateway (GW) and eavesdropper (Eve), and the non-linear energy harvesting (EH) model and energy-causality constraint at each backscatter user (BU) are considered. The energy outage probability and secrecy outage probability expressions are derived in the general case at first, then the closed-form expressions are obtained under the special scenario, i.e., the no-noise and the typical propagation loss scenario. Numerical simulations validate the analytical results and examine the impacts of various parameters on the secrecy performance. In particular, there exists an optimal reflection coefficient for secrecy outage probability minimization under certain conditions, and the optimal reflection coefficient increases with the increasing SIC coefficient at GW.

Secured End-to-End FSO-VLC-Based IoT Network With Randomly Positioned VLC: Known and Unknown CSI

In this article, we determine the secrecy performance of a dual-hop hybrid free space optics (FSO)-visible light communication (VLC) system with a randomly located legitimate Internet of Things (IoT)-based receiver in the presence of two distinct eavesdroppers (EDs). We consider one FSO-based ED located near the relay, wiretapping the FSO link. However, another ED wiretaps the information from the multiple VLC sources embedded on the ceiling of the room. We consider the three different scenarios for VLC-based ED: 1) the effect of uniformly distributed ED in the absence of any secured zone in the VLC coverage area; 2) the impact of uniformly distributed ED in the presence of VLC secured area; and 3) the effect of random waypoint (RWP) distributed ED on the system’s security. The secrecy performance of the system is evaluated based on known and unknown instantaneous channel state information (CSI) of EDs. Furthermore, the closed form expression for secrecy outage probability (SOP) in terms of Meijer’s-G and Gauss hypergeometric functions is derived. In order to have a better insight into the system’s performance, analytical results are expressed asymptotically in the high signal-to-noise ratio (SNR) regime. Following that, Monte Carlo simulations are done to validate the theoretical results. Additionally, a secrecy threshold is obtained in order to comprehend the system’s security and reliability.

Secrecy Outage Probability for Two-Way Integrated Satellite Unmanned Aerial Vehicle Relay Networks with Hardware Impairments

In this paper, we investigate the secrecy outage performance for the two-way integrated satellite unmanned aerial vehicle relay networks with hardware impairments. Particularly, the closed-form expression for the secrecy outage probability is obtained. Moreover, to get more information on the secrecy outage probability in a high signal-to-noise regime, the asymptotic analysis along with the secrecy diversity order and secrecy coding gain for the secrecy outage probability are also further obtained, which presents a fast method to evaluate the impact of system parameters and hardware impairments on the considered network. Finally, Monte Carlo simulation results are provided to show the efficiency of the theoretical analysis.

Secrecy Analysis of Uplink IM-OFDMA Systems in the Presence of IQ Imbalance

This paper introduces the secrecy analysis of the index modulation-based orthogonal frequency division multiple access (IM-OFDMA) schemes by considering the in-phase and quadrature imbalance (IQI) presence at the users' RF front ends. In particular, by assuming the existence of an eavesdropper, the secrecy performance of the considered uplink multiple-access system is investigated through the strictly positive secrecy capacity and secrecy outage probability, and closed-form expressions are derived for both quantities. Moreover, the secrecy performance is conducted regarding IQI compensation based on a preamble-based estimation method. Further, analysis of the impact of the different parameters of IM-OFDMA, IQI, and estimation method is included via analytical and simulation-based results. The results reveal that IM-OFDMA is more reliable in secrecy performance than OFDMA, regardless of whether IQI is present. Also, IQI compensation can lead to a better secrecy performance compared to the case of no IQI.

Secure Transmission Over Multiple Access Wiretap Channel by Cross-Time Interference Injection

Due to the openness of wireless communication, information transmitted in the multiple access channel is vulnerable to eavesdropping by illegitimate users. Classic artificial noise-assisted schemes can improve security but are not suitable for power-constrained users. To address this problem, we propose a cross-time interference injection scheme in this paper, which improves security by introducing cross-time self-interference and inter-user interference, and does not require artificial noise. The proposed scheme exploits the properties of the Hadamard matrix and the wireless channels, so that the eavesdropping channel suffers from stronger interference than the legitimate channel. We analyze the security performance when both the legitimate receiver and the eavesdropper exploit the successive interference cancellation (SIC) scheme, including the secrecy sum rate, the secrecy capacity, and the secrecy outage probability. We further investigate the effect of the number of eavesdropper’s antennas, the number of legitimate users, and the number of time slots used by the scheme on the security performance, and obtain the corresponding relationship between these parameters when achieving a positive secrecy rate. Finally, simulation results corroborate our theoretical analysis.

On the Performance Analysis of RIS-Assisted Infinite and Finite Blocklength Communication in Presence of an Eavesdropper

This work investigates the performance of a reconfigurable intelligent surface (RIS) aided communication system under ultra-reliable low-latency communication (URLLC) constraints, where the secrecy performance for communication with multiple legitimate users (D), scheduled one at a time, in presence of eavesdropper (E) is analyzed. The outage probability and block error rate (BLER) at D and E are derived for infinite and finite blocklength transmissions assuming that the direct communication links between source (S)-D and S-E exist. The expressions for the asymptotic outage probability, secrecy capacity, secrecy outage probability and secure BLER are also obtained. The new expressions for the probability density function (PDF) and the cumulative distribution function (CDF) for the difference of phases of two Nakagami-m distributed channel envelopes are derived. To validate the correctness of the derived analytical expressions and to analyze the impact of various system parameters including the number of RIS meta-atoms, the magnitude of reflection coefficient, transmit signal-to-noise ratio (SNR) threshold, and quantized phase-shifts, Monte-Carlo simulations are used. The performance of the proposed system is compared with that of the decode and forward relay-based system. It is also shown that RIS significantly improves the performance at D, whereas degrading the same for E.

Physical Layer Security of Dual-Hop Hybrid FSO-mmWave Systems

Hybrid free-space optical (FSO) and millimeter wave (mmWave) systems have been proposed as an efficient solution to improve spectral efficiency and maintain link reliability. The comparable supported data rate and the complementary characteristics in different weather conditions of both links, i.e., FSO and mmWave) have attracted research efforts towards analyzing the different performance aspects of hybrid FSO-mmWave systems. Following this direction, in this article, the physical-layer security analysis of the dual-hop hybrid FSO-mmWave systems is addressed. In the considered system, both FSO and mmWave links are simultaneously used to carry data at each hop, while an eavesdropper is assumed to present to wiretap either one or both links. The analysis includes building a mathematical framework to derive different secrecy metrics, such as the average secrecy capacity, secrecy outage probability and effective secrecy throughput metrics, in mathematical expressions. Obtained analytical results are verified using Monte Carlo simulations where exact matching are achieved. Moreover, the presented results include investigation of the impact of the different operational parameters on the overall secrecy performance.

Secrecy Outage Analysis of Relay Aided Multiuser Scheduling for Wireless Networks in the Face of Co-Channel Interference

In this paper, we analyze the secrecy outage probability of a relay aided multiuser network which consists of a cluster head (CH), a decode-and-forward (DF) relay, and multiple users in the presence of an eavesdropper and co-channel interference (CCI). Firstly, we propose two relay aided multiuser scheduling (RMS) schemes to improve the secrecy outage performance of the network by considering the availability of channel state information (CSI) of CCI links, including the partial CSI based RMS (PCSI-RMS) scheme and the full CSI based RMS (FCSI-RMS) scheme. For comparison purposes, the relay aided round-robin scheduling (RRRS) scheme is also employed as a baseline. Then, we derive closed-form expressions for the proposed PCSI-RMS and FCSI-RMS schemes as well as the RRRS scheme in terms of their exact and asymptotic secrecy outage probabilities over Rayleigh fading channels in the face of CCI. Finally, numerical results show that the secrecy outage performance of the proposed PCSI-RMS and FCSI-RMS schemes is better than that of the RRRS scheme, where FCSI-RMS achieves the best secrecy outage performance. With an increase of the number of users, the secrecy outage performance of the PCSI-RMS and FCSI-RMS schemes is significantly improved, while that of the RRRS scheme keeps unchanged, which demonstrates the benefits of adopting the proposed PCSI-RMS and FCSI-RMS schemes against eavesdropping in CCI environments. Moreover, there is an optimal power allocation factor between the CH and the relay, which makes the network have the best secrecy outage performance.

Physical Layer Security Performance of NOMA-Aided Vehicular Communications Over Nakagami-$m$ Time-Selective Fading Channels With Channel Estimation Errors

This paper considers a single-input-multiple-output non-orthogonal multiple access enabled vehicular communication system, and investigates its secrecy performance over time-selective fading and channel estimation errors. We formulate two scenarios considering the decoding ability at eavesdropper, viz., 1) Scenario I: when it has sufficient decoding capability, and 2) Scenario II: when its decoding capability can be the same as the legitimate vehicles. Under such a realistic system setup, we derive the secrecy outage probability (SOP) and ergodic secrecy capacity expressions for both legitimate vehicles and the overall system under both Scenarios I and II over Nakagami- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</i> fading channels. We then analyze the asymptotic SOP limits of both legitimate vehicles under Scenarios I and II, by formulating cases based on the average transmit signal-to-noise ratio and average channel gains associated with the main links and wiretap link. From the asymptotic analysis under these cases, it is observed that both legitimate vehicles do not achieve any secrecy diversity order even after leveraging the benefits of fading severity parameters and multiple antennas. We also formulate several special cases of interest to reveal some more insightful information about the system's secrecy performance. Finally, we corroborate our analytical and theoretical findings via simulation results.

Optical HAPS Eavesdropping in Vertical Heterogeneous Networks

In the next generation (6G) wireless networks, the integration of terrestrial and non-terrestrial networks is essential to provide flawless connectivity over the globe. The vital element of this architecture is the high altitude platform station (HAPS) systems, which can provide reliable and ubiquitous connectivity among satellites, unmanned aerial vehicles (UAVs), and terrestrial users. Motivated by the importance of HAPS systems, in this paper, we provide three different use-cases for HAPS eavesdropping scenarios and investigate their physical layer security (PLS) performances. To quantify the PLS performance of the proposed setups, we perform secrecy outage probability (SOP), probability of positive secrecy (PPSC), average secrecy capacity (ASC), and secrecy throughput (ST) analyses. Furthermore, we also provide important design guidelines that can be beneficial for secure HAPS systems.

Interference Alignment for Physical Layer Security in Multi-User Networks With Passive Eavesdroppers

We investigate the physical layer security (PLS) in multi-user interference networks. In particular, we consider secure transmission from a legitimate source (Alice) to a legitimate destination (Bob), coexisting with multiple passive eavesdroppers (Eves), as well as multiple legitimate transceivers. By assuming that only statistical channel state informations (CSIs) of Eves and local CSIs of legitimate users are available, we propose an artificial noise (AN) assisted interference alignment (IA) for security enhancement. Unlike traditional IA based security approaches which may result in secret signal cancellation, we design a modified alternating minimization (AM) scheme to overcome this threat, by incorporating the max-eigenmode beamforming (MEB) for secure transmission. Moreover, by partitioning the IA equation into three independent subsets and their combinations, a much tighter necessary condition for IA feasibility is established. We also provide guiding insights into the practical system designs, including useful guidelines for the selection of the dimension of AN. Furthermore, the power allocation ratio between the secret signal and the AN signal is optimized to minimize the secrecy outage probability (SOP), subject to a minimum secrecy rate constraint. Numerical results demonstrate that our design can enhance both quality and security of the secret signal, and thus is suitable and reliable for PLS in interference networks.

On the Secrecy Outage Probability of NOMA Systems Affected by Imperfect SIC over κ−μ Fading Channels

Fifth-generation (5G) and beyond fifth-generation (B5G) wireless systems increase the transmission capabilities of simple devices, such as Internet of Things (IoT) devices. However, they are vulnerable to eavesdropping attacks due to their low computational processing capacity. Thus, physical layer security (PLS) appears as an interesting alternative essential for their proper operation. In this work, the secrecy performance of power-domain non-orthogonal-multiple-access (NOMA) systems affected by imperfect successive interference cancellation (SIC) is evaluated in a scenario consisting of two users operating over κ−μ fading channels. By considering that the user furthest from the base station (BS) is an untrusted user, expressions to calculate the signal-to-noise-plus-interference ratio (SNIR) of both users are derived, and with these results, an expression to evaluate the secrecy-outage-probability (SOP) for the trusted user is derived. Numerical results using Monte-Carlo simulations are carried out in some scenarios to validate the derived expressions. The results also evidence a simple strategy to minimize the SOP for the trusted user based on the κ and μ fading parameters.