Secrecy Outage Research Articles

Secrecy Performance of Underlay Cognitive Radio Networks With Primary Interference

This work explores the physical layer security of an underlay cognitive radio network (CRN) in the presence of a powerful interferer called a primary transmitter (PT) under peak interference power constraint. Under this scenario, the secondary transmitter (Alice) transmits secret information on a single antenna with the highest signal-to-interference plus noise ratio (SINR) to a legitimate receiver (Bob), and an eavesdropper (Eve) attempts to intercept that information. Depending upon the availability of channel state information (CSI) of the eavesdropper channel, we investigate the secrecy performance of the proposed network in the Rayleigh fading environment for both passive and active eavesdropping scenarios. We obtain analytical expressions for the secrecy outage probability, intercept probability, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\epsilon$</tex-math></inline-formula> -outage secrecy capacity in a passive eavesdropping scenario. A complete investigation of the average secrecy capacity (ASC) has been made, and novel expressions for the exact and asymptotic ASC have been obtained for active eavesdropping. Bolstering these results, we also define a high SINR power offset, which quantifies the significance of main system parameters on the ASC explicitly. Further, the effect of outdated CSI of Alice to primary receiver link on the various performance metrics with the concept of interference-outage is also studied.

A Secure Energy Efficient Scheme for Cooperative IoT Networks

A secure energy efficient approach is proposed to connect Internet of Things (IoT) sensors that operate with limited power resources. This is done by optimizing simultaneously the energy efficiency, the communication rate and the network security while limiting the potential data leakage and tracking the finite battery status evolution. The proposed model uses spatial diversity in addition to artificial jamming introduced by an intermediate device to forward the data from the sensors to the destination and to secure the communication links without draining the rechargeable batteries. The energy harvested by the source is also maximized without affecting the security level of the network. The outage secrecy capacity is derived to evaluate the security level. Furthermore, the system power stability is analyzed using Markov chains and statistical approaches to validate the efficiency of the proposed technique in maintaining the system in a self-sufficient mode and making it operate without the assistance of external power resources.

When Satellites Work as Eavesdroppers

This paper considers <i>satellite eavesdroppers</i> in uplink satellite communication systems where the eavesdroppers are randomly distributed at arbitrary altitudes according to homogeneous binomial point processes and attempt to overhear signals that a ground terminal transmits to a serving satellite. Non-colluding eavesdropping satellites are assumed, i.e., they do not cooperate with each other, so that their received signals are not combined but are decoded individually. Directional beamforming with two types of antennas: fixed- and steerable-beam antennas, is adopted at the eavesdropping satellites. The possible distribution cases for the eavesdropping satellites and the distributions of the distances between the terminal and the satellites are analyzed. The distributions of the signal-to-noise ratios (SNRs) at both the serving satellite and the most detrimental eavesdropping satellite are derived as closed-form expressions. The ergodic and outage secrecy capacities of the systems are derived with the secrecy outage probability using the SNR distributions. Simpler approximate expressions for the secrecy performance are obtained based on the Poisson limit theorem, and asymptotic analyses are also carried out in the high-SNR regime. Monte-Carlo simulations verify the analytical results for the secrecy performance. The analytical results are expected to be used to evaluate the secrecy performance and design secure satellite constellations by considering the impact of potential threats from malicious satellite eavesdroppers.

On the Performance of Power Beacon-Assisted D2D Communications in the Presence of Multi-Jammers and Eavesdropper

In this work, we investigate the performance analysis of a device-to-device (D2D) communication network under an eavesdropper E attack. Besides, we assume that E is located in the proximal region where it can overhear the information from the source S. Specifically, S transmits information to the destination D, adopting the power beacon's energy to surmount the limited energy budget. Moreover, to reduce the quality of the eavesdropping link, the cooperative jamming technique can be used, where the multi-friendly jammers are employed to generate the artificial noises to E continuously. As considering the above presentation, we derive the quality of system analysis in terms of the outage probability (OP), intercept probability (IP), and secrecy outage probability (SOP) of the proposed system model. Finally, the Monte-Carlo simulations are performed to corroborate the exactness of the mathematical analysis.This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

Low-Complexity Transmit Power Control for Secure Communications in Wireless-Powered Cognitive Radio Networks.

In this study, wireless-powered cognitive radio networks (WPCRNs) are considered, in which N sets of transmitters, receivers and energy-harvesting (EH) nodes in secondary networks share the same spectrum with primary users (PUs) and none of the EH nodes is allowed to decode information but can harvest energy from the signals. Given that the EH nodes are untrusted nodes from the point of view of information transfer, the eavesdropping of secret information can occur if they decide to eavesdrop on information instead of harvesting energy from the signals transmitted by secondary users (SUs). For secure communications in WPCRNs, we aim to find the optimal transmit powers of SUs that maximize the average secrecy rate of SUs while maintaining the interference to PUs below an allowable level, while guaranteeing the minimum EH requirement for each EH node. First, we derive an analytical expression for the transmit power via dual decomposition and propose a suboptimal transmit power control algorithm, which is implemented in an iterative manner with low complexity. The simulation results confirm that the proposed scheme outperforms the conventional distributed schemes by more than 10% in terms of the average secrecy rate and outage probability and can also considerably reduce the computation time compared with the optimal scheme.

AN‐aided probabilistic robust and secure beamforming with imperfect LCSI and statistical ECSI

The probabilistic robust beamforming with the help of artificial noise (AN) is investigated in this study, where a multiple-input-single-output wiretap scenario with K single-antenna eavesdroppers is considered. Based on a more practical assumption that the transmitter derives imperfect legitimate user's channel state information (LCSI) and statistical eavesdroppers' channel state information (ECSI), secrecy rate maximisation (SRM) under a total transmit power constraint and K probabilistic secrecy outage constraints are studied. To deal with it, the K probabilistic constraints are firstly approximated to the deterministic worst-case ones by resorting to sphere bounding. Secondly, by introducing a slack variable the approximated worst-case SRM can be further recast as a series of semi-definite programmings. In this way, the jointly optimised robust beamforming vector and the AN covariance are determined in a tractable convex fashion. Moreover, the authors can prove that the derived AN-aided secure robust beamforming actually is the optimal solution to the approximated worst-case SRM problem. Numerical results reveal that the proposed AN-aided probabilistic secure robust beamforming could achieve outage secrecy rate improvement in comparison with the existing optimal worst-case robust beamforming without AN, optimal outage constrained robust beamforming without AN, the non-robust isotropic AN transmission, and the non-robust AN-aided beamforming scheme.

Secure Transmission in Cognitive Wiretap Networks with Full-Duplex Receivers

This paper studies the secure transmission in the dual-hop cognitive wiretap networks, where the secondary transmitter (Alice) aims to transmit confidential information to the secondary receiver (Bob) in the face of a multi-antenna relay (Relay), while the malicious eavesdropper (Eve) is used to eavesdrop the confidential information from Alice and Relay. To improve security, we design two transmission schemes, namely maximal-ratio combining/maximal-ratio transmission-selection combining (MRC/MRT-SC) with half-duplex (HD) receiver and maximal-ratio combining-zero forcing beamforming/maximal-ratio transmission-selection combining-zero forcing beamforming (MRC-ZFB/MRT-SC-ZFB) with full-duplex (FD) receiver. To evaluate the secrecy performance obtained from the proposed schemes comprehensively, the new closed-form and simple asymptotic expressions for the secrecy outage probability (SOP) and secrecy throughput (ST) of our considered networks with MRC-ZFB/MRT-SC-ZFB and MRC/MRT-SC schemes are derived, respectively. Thus, we explore the effect of various schemes on system secrecy performance in terms of SOP and ST. Analytical results and numerical simulations demonstrate that MRC-ZFB/MRT-SC-ZFB achieves better performance in the two proposed schemes. In particular, we show that the FD receiver plays a crucial role in designing the cognitive wiretap networks for protecting the legitimate link against attack from the malicious eavesdropping.

On Residual Energy Maximization in DF Cognitive Radio Networks With Multiple Eavesdroppers

This paper explores the issues of energy harvesting (EH) and multiple eavesdropping in an underlay cognitive radio network (CRN) that comprises of a secondary transmitter ( $SU_{\mathcal {T}}$ ) and destination ( $SU_{\mathcal {D}}$ ) node connected through a decode-forward (DF) relay ( $S_{\mathcal {R}}$ ). CRN is operated following a frame structure that includes three non-overlapping slots where in the first one, the relay harvests energy from the information signal of $SU_{\mathcal {T}}$ and the interference signal of primary user (PU). During the second slot, $SU_{\mathcal {T}}$ transmits data to the relay node. In the last slot, $S_{\mathcal {R}}$ forwards the same to $SU_{\mathcal {D}}$ and $SU_{\mathcal {T}}$ does EH from PU signal. Residual energy maximization is done under the constraints of energy causality for $SU_{\mathcal {T}}$ and $S_{\mathcal {R}}$ , interference to PU, secondary outage probability and secrecy outage probability. Analytical expressions of ergodic secrecy capacity and secrecy outage probability are derived for non-colluding (NCE) and colluding eavesdropping (CE) scenarios. Closed form expressions for the optimal transmit power of $SU_{\mathcal {T}}$ and $S_{\mathcal {R}}$ along with the time slot for EH are derived and their impacts on the residual energy, secondary outage probability and secrecy outage probability are analysed. Simulation results show a gain on the maximum value of the residual energy by ~8.13% for CE and ~4.72% for NCE over the existing works.

Resource allocation for secure Gaussian parallel relay channels with finite-length coding and discrete constellations

We investigate the transmission of a secret message from Alice to Bob in the presence of an eavesdropper (Eve) and many of decode-and-forward relay nodes. Each link comprises a set of parallel channels, modeling for example an orthogonal frequency division multiplexing transmission. We consider the impact of efficient implementations, including discrete constellations and finite-length coding, defining an achievable secrecy rate under a constraint on the equivocation rate at Eve. Then, we propose a power and channel allocation algorithm that maximizes the achievable secrecy rate by resorting to two coupled Gale-Shapley algorithms for stable matching problem. We consider the scenarios of both full and partial channel state information at Alice. In the latter case, we only guarantee an outage secrecy rate, i.e., the rate of a message that remains secret with a given probability. Numerical results are provided for Rayleigh fading channels in terms of average outage secrecy rate, showing that practical schemes achieve a performance quite close to that of ideal ones.

Physical Layer Security in Nonorthogonal Multiple Access Wireless Network with Jammer Selection

The physical layer security of downlink nonorthogonal multiple access (NOMA) network is analyzed. In order to improve the secrecy probability, friendly jammers are jointed in the NOMA network. Two jammer schemes are proposed in the NOMA network. All the jammers transmit jamming signal without jammer selection in the first scheme (NO JS scheme). Jammers are selected to transmit jamming signal if their interfering power on scheduled users is below a threshold in the second scheme (JS scheme). A stochastic geometry approach is applied to analyze the outage probability and the secrecy probability. Compared with the NO JS scheme and traditional scheme (without jointing jammers), the jammer selection scheme provides a good balance between the user outage probability and secrecy probability. Numerical results demonstrate that the security performance of the two proposed schemes can be improved by jointing the jammers in the NOMA wireless network.

Secure transmission in underlay cognitive radio network with outdated channel state information

This paper investigates the secrecy performance of an underlay cognitive radio network (CRN) with outdated channel state information (CSI) for two practical scenarios, i.e., scenario 1: the CSI of an eavesdropper’s channel is unavailable at the secondary transmitter and scenario II: the CSI of an eavesdropper is available at the secondary transmitter. The selection combining (SC) and maximal ratio combining (MRC) techniques are utilized at the secondary receiver while MRC is also employed at both eavesdropper and primary receiver. For the scenario I, the compact expressions of exact and asymptotic secrecy outage probability (SOP), intercept probability and ϵ- outage secrecy capacity are derived, and simulations are conducted to verify analytical results. Our results reveal that the secrecy performance of the system degrades when the CSI of the main channel is outdated. Additionally, in scenario II, a comprehensive analysis of average secrecy capacity is performed, and new closed-form expressions for exact and asymptotic average secrecy capacity are derived which are valid for an arbitrary number of antennas at secondary receiver and eavesdropper. Finally, we investigate the high signal to noise ratio (SNR) slope and high SNR power offset which characterize the impact of the outdated CSI of the main channel and eavesdropper’s channel on average secrecy capacity.

Secrecy Rate Analysis Against Aerial Eavesdropper

This paper studies the threat that an aerial eavesdropper can pose to terrestrial wireless communications, from an information-theoretic point of view. The achievable ergodic and the average $\epsilon $ -outage secrecy rates with no channel state information at the transmitter (i.e., with no CSIT) are analyzed for a transmitter–receiver pair on the ground, in the presence of an aerial eavesdropper which flies a random trajectory following a smooth turn (ST) mobility model in a three-dimensional (3D) space. The ST mobility model induces a uniform distribution (of the eavesdropper’s waypoints) within the considered 3D volume. Closed-form asymptotic approximations of the achievable secrecy rates are derived based on the almost sure convergence and non-trivial mathematical manipulations. Validated by simulations, our analysis is tight and reveals that the ground transmission is particularly vulnerable to aerial eavesdropping which can be carried out in a distance without being noticed. 3D spherical regions are identified, within which the secrecy rates vanish. This sheds useful insights to protect terrestrial wireless networks from aerial eavesdropping.

Secrecy Performance of Terrestrial Radio Links Under Collaborative Aerial Eavesdropping

Motivated to understand the increasingly severe threat of unmanned aerial vehicles (UAVs) to the confidentiality of terrestrial radio links, this paper analyzes the ergodic and $\epsilon $ -outage secrecy capacities of the links in the presence of multiple cooperative aerial eavesdroppers flying autonomously in three-dimensional (3D) spaces and exploiting selection combining (SC) or maximal ratio combining (MRC). The “cut-off” density of the eavesdroppers under which the secrecy capacities vanish is identified. By decoupling the analysis of the random trajectories from the random channel fading, closed-form approximations with almost sure convergence to the secrecy capacities are devised. The analysis is extended to study the impact of the oscillator phase noises and finite memories of the aerial eavesdroppers on the secrecy performance of the ground link. Validated by simulations, the cut-off density only depends on the range of the link in the case of SC eavesdropping, while it depends on the flight region of the eavesdroppers in the case of MRC eavesdropping.

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.

Secrecy Analysis of Modify-and-Forward Relaying With Relay Selection

This paper investigates the physical-layer security of the modify-and-forward (MF) protocol in multi-relay and multieavesdropper networks. Three relay selection critera are developed according to the channel state information (CSI) acquisition. CriterionI requires the CSI of all main channels for relay selection. Criteria II and III rely only on the CSI of the source-relay and relay-destination channels, respectively. We derive the exact secrecy outage probability (SOP), probability of nonzero secrecy capacity, and the ergodic secrecy rate in the closed forms. The €-outage secrecy capacity is also evaluated. Asymptotic analysis of the SOP explicitly reveals that the secrecy diversity order of criterionI depends on the total number of relays, whereas those of criteriaII and III are 2 and 1, respectively. The probability of nonzero secrecy capacity asymptotically decreases with the SNR of the wiretap channel as the eavesdropper is close to the source and relays. CriterionI is always superior to criteriaII and III in terms of the ergodic secrecy rate and €-outage secrecy capacity. Simulations results also demonstrated that the €-outage secrecy capacity deteriorates as the SNR of the eavesdropper's channel increases.

Dynamic power allocation scheme with clustering based on physical layer security

Achieving large confidential capacity under the wiretap channel model is a challenge due to the narrow modulation bandwidth and total transmission power constraints. The confidential capacity of a system can be improved through a non-orthogonal multiple access technique that can obtain the highest transmission power in a downlink network. A clustering method is applied to network users who require data with similar contents. Based on the channel gain of each user, cluster heads are selected as agents for the corresponding clusters; then, the total transmission power is shared among the cluster heads. Before the power allocation process, the signal-to-interference-plus-noise ratio of the cluster heads is derived by considering clipping noise to ensure fairness. On this basis, an optimal power allocation scheme is proposed using Lagrangian dual theory. A case is presented to validate the performance of the proposed power allocation scheme. The comparison of the numerical results with those of other schemes shows that the proposed method achieves better performance regarding both secrecy sum capacity and outage probability.

Managing Physical Layer Security in Wireless Cellular Networks: A Cyber Insurance Approach

The fifth-generation (5G) wireless networks are expected to provision value-added services with ubiquitous coverage, which makes data security unprecedentedly critical. In this context, physical layer security has emerged as a promising solution to safeguard data transmission by exploiting characteristics of the wireless medium. Despite the recent technological advance in physical layer security and wireless transmission, secrecy outages (i.e., data breaches) and service outages (i.e., connection failures) will inevitably happen and incur financial losses. This economical consequence is a fact that is mostly overlooked by the existing literature. To provide financial protection against secrecy outage and service outage, we introduce a cyber-insurance framework for wireless users in cellular networks, where each user pays a premium to an insurer for a future financial compensation if an outage occurs to him/her. In particular, we derive the network risks of the cellular users in terms of secrecy outage probability and service outage probability as well as the financial risk of the cyber insurer in terms of the ruin probability that indicates the chance that the insurer experiences a deficit in affording the losses of outage users. Through numerical evaluation, we demonstrate the impact of network performance on the financial risk of the insurer. The numerical results also show that the ruin probability of the insurer can be effectively reduced by equipping a larger number of antennas at the base stations or increasing network frequency reuse.

Energy-Efficiency Maximization for Secure Multiuser MIMO SWIPT Systems With CSI Uncertainty

This paper studies the secure transmission issue for simultaneous wireless information and power transfer in a multiuser multiple-input-multiple-output system with multiple external eavesdroppers, where the transmitter broadcasts independent confidential messages to different legitimate receivers. Each receiver can be seen as an internal eavesdropper intended by other receivers. Our objective is to achieve the robust beamforming design under imperfect channel state information, in which the total transmission power is minimized with constraints on the achievable secrecy rate and the energy harvesting. Since the problem is nonconvex, we propose a two-level optimization scheme. For the inner problem, we investigate two conservative relaxation approaches, large-deviation inequality and Bernstein-type inequality (BTI), to reformulate the outage secrecy rate constraints into some convex ones, yielding a convex optimization by semidefinite programming (SDP) relaxation. For the outer problem, it is a K-variable optimization problem, which can be solved via the novel line-dimensional-like search method. Moreover, we characterize the rank profile of SDP relaxed solution for these two approaches. Specifically, the optimal solution is proved to be rank-one. Numerical results are provided to verify the performance of the proposed algorithms, where the LDI-based scheme outperforms the BTI-based scheme in terms of energy efficiency.

Outage Constrained Robust Energy Harvesting Maximization for Secure MIMO SWIPT Systems

In this letter, we investigate the outage constrained robust secure design in multiple-input multiple-output simultaneous wireless information and power transfer systems, where the energy receivers (ERs) may eavesdrop the confidential information sent to the desired receivers (DRs). Specifically, we propose a joint design of the precoding matrix and the power splitting (PS) ratios at the DRs to maximize the total harvested energy at the DRs, under the outage secrecy rate constraints at the DRs and the outage harvested energy constraints at the ERs. To solve the formulated non-convex maximize the sum of non-linear functions problem, we decouple the original problem into two sub-problems and propose an alternating optimization algorithm, wherein large deviation inequality and successive convex approximation are used to handle these sub-problems. Finally, numerical results are provided to validate our proposed algorithm.

Adapting Rate and Power for Maximizing Secrecy Energy Efficiency

We present the optimum rate and power adaptation rule that maximizes the average secrecy energy efficiency (SEE) subject to an average transmission power constraint. The SEE is defined as the outage secrecy capacity, the largest secrecy rate, such that the outage probability is less than a certain value, divided by the total power consumption (bits per joule). We characterize the SEE gain provided by varying the rate and/or the power, and discuss the impact of the number of antennas on the optimum adaptation rule.