Secrecy Trade-off at the Physical Layer over Mixed Fading Multicast Channels Employing Antenna Diversity

This paper deals with the secrecy performance analysis of a multicast network over mixed fading scenarios in which a cluster of passive eavesdroppers is trying to overhear the secret transmission. Our key contribution is to prevent this malicious attack of the illegitimate receivers. Rayleigh/ Rician mixed fading channels are considered to model alternately the multicast/ eavesdropper and eavesdropper/ multicast channels as such mixed fading scenarios are often encountered in cellular communication where only one link (either multicast or eavesdropper) undergo a line-of-sight propagation path. At first, we derive the probability density functions for the single-input-multiple-output multicast scenarios and then the secrecy analysis is carried out by obtaining closed-form expressions for the performance matrices such as the probability of non-zero secrecy multicast capacity, ergodic secrecy multicast capacity, and secure outage probability for multicasting. The derived expressions are beneficial to investigate how the antenna diversity can combat the detrimental impact of fading as well as the number of multicast users and eavesdroppers, and improve the secrecy level to the acceptable limit. Moreover, the best secure scenario in terms of the secrecy parameters is obtained when the multicast channels undergo Rician fading whereas the eavesdropper channels experience Rayleigh fading. Finally, the analytical expressions are justified via the Monte-Carlo simulations.

     

Transmit antenna selection of correlated MIMO multiuser cognitive radio networks in Nakagami‐m fading channels

In this paper, we examine the impact of antenna correlation on transmit antenna selection with receive maximal ratio combining (TAS/MRC) in multiple‐input multiple‐output multiuser underlay cognitive radio network (MIMO‐MCN) over a Nakagami‐m fading environment. The secondary network under consideration consists of a single source and M destinations equipped with multiple correlated antennas at each node. The primary network composed of L primary users, each of which is equipped with multiple correlated antennas. For the considered underlay spectrum sharing paradigm, the transmission power of the proposed secondary system is limited by the peak interference limit on the primary network and the maximum transmission power at the secondary network. In particular, we derive exact closed‐form expressions for the outage probability and average symbol error rate of the proposed secondary system. To gain further insights, simple asymptotic closed‐form expressions for the outage probability and symbol error rate are provided to obtain the achievable diversity order and coding gain of the system. In addition, the impact of antenna correlation on the secondary user ergodic capacity has been investigated by deriving closed‐form expressions for the secondary user capacity. The derived analytical formulas herein are supported by numerical and simulation results to clarify the main contributions. Copyright © 2016 John Wiley & Sons, Ltd.     

Analysis of secrecy outage performance for full duplex NOMA relay systems with appearance of multiple eavesdroppers

Full-duplex (FD) relay systems including a transmit antenna selection and a non-orthogonal multiple access (NOMA) methods are analyzed under presence of multiple eavesdroppers. A channel state information of both the considered system and eavesdroppers is assumed to be outdated and eavesdroppers eavesdrop information signals independently. A closed-form of secure outage probability (SOP), secrecy throughput of every user is derived to evaluate the secrecy performance, and the mathematical analysis approach is verified by the Monte-Carlo simulation. Furthermore, the Golden-Section Search algorithm is proposed to find the maximum of the secrecy throughput of the considered FD-NOMA system. Numerical results indicate that there exists the SOP floor in the considered system and it is constrained by the channel gain of near user. Moreover, there is the optimal signal to interference plus noise ratio value which minimizes the SOP of the system regardless of the number of eavesdroppers. In comparison with half-duplex NOMA model, the SOP of FD-NOMA model is better.

     

A New Relay and Jammer Selection Schemes for Secure One-Way Cooperative Networks

This paper presents different relay and jammer selection schemes for one-way cooperative networks to increase the security against malicious eavesdroppers. We consider a single source-destination cooperative network with multiple intermediate nodes and one or more eavesdroppers. The selection in the proposed schemes is made with the presence of direct links and the assumption that the broadcast phase is unsecured. The proposed schemes select three intermediate nodes. The first selected node operates in the conventional relay mode and assists the source to deliver its data to the corresponding destination via a Decode-and-Forward strategy. The second and third selected nodes are used in different communication phases as jammers to create intentional interference at the eavesdroppers’ nodes. Moreover, a hybrid scheme which switches between jamming and non-jamming modes is introduced in this paper. The proposed schemes are analyzed in terms of ergodic secrecy capacity and secrecy outage probability. Extensive analysis and a set of simulation results are presented to demonstrate the effectiveness of the different schemes presented in this work. The obtained results show that the proposed schemes with jamming outperform the conventional non-jamming schemes and the hybrid switching scheme further improves the secrecy capacity. The impact of changing both the eavesdroppers and the relays location on ergodic secrecy capacity and secrecy outage probability is also discussed. Finally, the impact of the presence of multiple eavesdroppers is studied in this paper.     

Secrecy performance analysis on cooperative CR-NOMA network

In order to improve the secrecy performance of communication system and make efficient use of limited spectrum,overlay cognitive radio (OCR) technology was combined with non-orthogonal multiple access (NOMA) technology and the communication model was proposed,in which secondary network realized dynamic switching between assisting primary network communication and secondary network communication by sensing whether the primary user occupied the spectrum or not.Artificial noise (AN) aided technology was used in primary and secondary networks respectively to further improve the secrecy performance of the system.The secrecy performance of the system was studied by deducing the expressions of the primary and secondary network secrecy outage probability and secrecy throughput respectively.The simulation results show that the proposed cognitive cooperative NOMA communication scheme is beneficial in reducing secrecy outage probability and increasing secrecy throughput.Furthermore,the influence of AN power allocation factor on system performance is given.     

多天线频谱共享认知网络保密中断概率分析

针对单输入多输出认知无线电网络,研究了瑞利衰落信道下采用最大比合并时保密中断性能。在所研究的系统中,次用户发射机发送机密信息给另一个次用户接收机,次用户接收机配备多个天线并且采用最大比例合并多个接收信号。同时,拥有多个天线窃听者也采用最大比合并方案偷听次用户发射机和次用户接收机之间传送的信息。频谱共享下次用户发射机工作时必须保证主用户的服务质量。推导了保密中断概率的精确表达式,分析了系统保密中断概率渐近性能。仿真结果验证了分析的正确性。     

On the secrecy performance of integrated satellite‐aerial‐terrestrial networks

This paper investigates secure transmission of an integrated satellite‐aerial‐terrestrial network (ISATN), where multiple eavesdroppers (Eves) attempt to overhear the satellite signals cooperatively. The ISATN adopts an unmanned aerial vehicle (UAV) equipped with multiple antennas as a relay with threshold‐based decode‐and‐forward (DF) protocol. By assuming that perfect instantaneous channel state information (CSI) of the satellite‐UAV link and the statistical CSI of the UAV‐user link are available, we first propose a beamforming (BF) scheme for maximizing the achievable secrecy rate (ASR) of the considered network. Then, we derive the analytical expressions of the secrecy outage probability (SOP) and ergodic secrecy rate (ESR) of the considered system with the BF strategy under an assumption that the satellite‐UAV link undergoes the shadowed‐Rician fading, while the UAV‐user link experiences the correlated Rayleigh fading. Finally, numerical results are given to demonstrate the superiority of the proposed BF scheme against zero forcing (ZF) and maximal ratio transmission (MRT) schemes and the validity of the secrecy performance analysis.     

D2D underlay massive MIMO hybrid networks with improved physical layer secrecy and energy efficiency

For us to meet the green and reliable communication requirement by the forthcoming fifth generation mobile networks, this paper focuses on a secrecy constrained device‐to‐device (D2D) underlay massive multiple‐input multiple‐output hybrid network, where the D2D user (DU) and cellular user (CU) links are exposed to passive malicious eavesdroppers. The D2D transmitters harvest the power from the signals of dedicated power beacons (PBs), but also the ambient radio frequency (RF) interference of CUs. The signals of PBs are known previously at the receivers of both the D2D and cellular users but are not known at eavesdroppers so that it can be regarded as an artificial noise. For the interested hybrid networks, we first present an energy‐harvesting scheme based on the inversion power control where the power received at the corresponding receiver is higher than the receiver's sensitivity. Then, by modeling the locations of network elements as Poisson point process and applying stochastic geometry, we derive the sufficient probability that a typical D2D transmitter harvests sufficient energy to establish communication links. Finally, with the derived sufficient probability, we evaluate the performance of the CUs and DUs in the achievable ergodic rate and the secrecy outage probability. Both the analytical and simulated results show that precious power of network is saved because of the ambient RF interference exploited, and the secrecy of both D2D and cellular links is improved simultaneously because of the signal of PBs modeled as artificial noises at CUs and DUs.     

Physical layer security for dual‐hop FSO/RF system using generalized ΓΓ/η−μ fading channels

We investigate the physical layer security of decode‐and‐forward–relayed free space optics (FSO)/radio frequency (RF) communication system. In this network, the eavesdropper exists after relay node and overhears RF transmission. Further, FSO being a line‐of‐sight transmission is assumed to be secure from eavesdroppers. Here, we have the Gamma‐Gamma (ΓΓ) distribution for FSO link and generalized η?μ distribution for RF link. The security for information transmission to the legitimate user in the presence of an eavesdropper is measured in terms of secrecy capacity and secrecy outage probability. Deriving the probability density function and cumulative distribution function of end‐to‐end signal‐to‐noise ratio, the closed‐form expressions for security parameters are achieved. The numerical analysis of the proposed system is done under the influence of atmospheric turbulence effects and various fading conditions. The results have been verified through simulation.     

A Cooperative Transmission Scheme for the Secure Wireless Multicasting

In this paper, a wireless multicast scenario with secrecy constraints is considered, where the source wishes to send a common message to two intended destinations in the presence of a passive eavesdropper. One destination is equipped with multiple antennas, and all of the other three nodes are equipped with a single antenna. Different to the conventional direct transmission, we propose a cooperative transmission scheme based on the cooperation between the two destinations. The basic idea is to divide the multicast scenario into two cooperative unicast transmissions at two phases and the two destinations help each other to jam the eavesdropper in turns. Such a cooperative transmission does not require the knowledge of the eavesdropper’s channel state information. Both analytic and numerical results demonstrate that the proposed cooperative scheme can achieve zero-approaching outage probability.     

Impact of channel estimation-and-artificial noise cancellation imperfection on artificial noise-aided energy harvesting overlay networks

EHONs (Energy Harvesting Overlay Networks) satisfy stringent design requirements such as high energy-and-spectrum utilization efficiencies. However, due to open access nature of these networks, eavesdroppers can emulate cognitive radios to wire-tap legitimate information, inducing information security to become a great concern. In order to protect legitimate information against eavesdroppers, this paper generates artificial noise transmitted simultaneously with legitimate information to interfere eavesdroppers. Nonetheless, artificial noise cannot be perfectly suppressed at legitimate receivers as for its primary purpose of interfering only eavesdroppers. Moreover, channel information used for signal detection is hardly estimated at receivers with absolute accuracy. As such, to quickly evaluate impact of channel estimation-and-artificial noise cancellation imperfection on secrecy performance of secondary/primary communication in ANaEHONs (Artificial Noise-aided EHONs), this paper firstly proposes precise closed-form formulas of primary/secondary SOP (Secrecy Outage Probability). Then, computer simulations are provided to corroborate these formulas. Finally, various results are illustrated to shed insights into secrecy performance of ANaEHON with key system parameters from which optimum parameters are recognized. Notably, secondary/primary communication can be secured at different levels by flexibly adjusting various parameters of the proposed system model.

     

Non-intrusive Cognitive Radio Using Adaptive Nulls-Steering

In this paper, we propose an adaptive non-intrusive cognitive radio network based on smart antenna technologies. The cognitive transmitter (CT), which is equipped with antenna array, first estimates and tracks the composite steering vectors of each primary (licensed) user. In what follows, CT forms transmit beamforming to place nulls to primary receivers based on the estimated spatial signatures. Moreover, we extensively analyze performance degradation caused by spatial signatures mismatch (estimation error) and verify that the proposed robust nulls-steering beamformer can comprehensively alleviate the mismatch effect. Simulation results demonstrate convergence of the proposed gradient-based recursive least squares algorithm. Furthermore, we have shown that outage probability can be kept extremely low under appropriate array size, which ensures the practicability of the proposed scheme.     

NOMA-D2D协作无线系统的物理层安全

针对未来海量用户设备接入的物理层安全（physical layer security，PLS）应用需求，提出了一种组合非正交多址接入（non-orthogonal multiple access，NOMA）、终端直通（device-to-device，D2D）与中继协作的NOMA-D2D协作无线系统PLS模型。该模型由采用发射天线选择（transmit antenna selection，TAS）的基站、分别作为基站和D2D发射端的NOMA远端蜂窝用户、D2D接收端以及被动窃听者组成，其中的D2D发射端承担基站的 NOMA 近端用户和解码转发中继两种角色。利用高斯—切比雪夫正交定理推导两种 TAS 方案下NOMA-D2D协作无线系统的安全中断概率、非零安全容量概率以及渐近安全中断概率的近似表达式。数值计算和仿真实验验证了NOMA-D2D协作无线系统PLS性能分析的准确性；在基站总功率恒定时增大分配给远端蜂窝用户的功率能有效提升NOMA-D2D协作无线系统的PLS性能。     

全双工协作多播业务在NOMA系统中的应用和性能

研究了多播业务在协作非正交多址接入（non-orthogonal multiple access,NOMA）系统中的应用及其性能。在一个单播和多播混合业务的场景中,多播用户组中选择某个信道状态最好的用户作为中继进行解码转发单播用户的信号,并在中继用户支持全双工的模式下,分析和推导了单播用户的中断概率和平均可达速率的闭式表达式。蒙特卡洛仿真结果和理论推导高度一致,表明提出的协作多播应用可以极大改善单播用户的中断性能,且多播用户的容量性能在中继发射功率不是很高的情况下不会受到影响。     

过时CSI下全双工中继辅助D2D网络的物理层安全

中继辅助终端直通（devicetodevice,D2D）网络通过与蜂窝网络共享频谱提高D2D用户的频谱效率和蜂窝用户（cellular user,CU）的物理层安全性。为进一步改善其性能,可以在基站和D2D链路的中继节点采用天线选择以及在中继节点采用全双工技术。然而,由于存在反馈时延和移动性,用于蜂窝链路和所有D2D链路天线选择的信道状态信息（channelstateinformation,CSI）均可能是过时的,针对该场景下的物理层安全性和可靠性问题,提出一种主动窃听和过时CSI场景下基站和中继节点均采用发射天线选择的全双工中继辅助D2D网络安全模型,推导CU的中断概率、遍历容量、非零安全容量概率、安全中断概率、渐近安全中断概率的解析表达式。数值计算与仿真结果均表明,基站发射天线数、中继干扰天线数越多,CU的安全性能越好;过时的CSI会降低CU的中断性能和安全性能。     

Outage Capacity for Secondary Users Due to Bandwidth Fluctuations: Multicarrier Versus Single Carrier

In this work we study the channel capacity from the point of view of a secondary user that shares the bandwidth of the channel with a primary user using dynamic spectrum access in cognitive radio.The secondary user sees bandwidth fluctuations (i.e, at any given time the bandwidth can be available or not) that impact its channel capacity. We study the outage capacity for the secondary user considering two scenarios in which the secondary user uses either a single carrier modulation for the case in which bandwidth fluctuates over the complete transmission band, and a multicarrier modulation for the case in which bandwidth fluctuations are over various transmission subbands. We derive expressions for the outage capacity of the secondary user for both single carrier and multicarrier. Results show that: (1) The outage capacity for single carrier can be higher than for multicarrier, but with a higher outage probability for single carrier than for multicarrier. In fact, a low value of outage probability for single carrier requires a duty cycle for the secondary user close to one, but this has the problem that it leaves a very short duty cycle for the primary user. (2) Although for the secondary user the outage capacity for multicarrier is smaller than for single carrier, for multicarrier lower values of the outage probability can be achieved even for short values of the duty cycle of the secondary user, allowing larger duty cycle values of the primary user. (3) For multicarrier, the outage capacity is more sensitive to changes in the duty cycle than to changes in the outage probability. To obtain a larger outage capacity with low values of both the outage probability and the duty cycle, it requires the use of a large number of subbands.     

Secrecy outage probability of inter‐vehicular cognitive radio networks

Herein, we consider an underlay cognitive radio network (CRN) where mobile secondary user wishes to transmit a confidential information to the secondary destination in the presence of an illegitimate eavesdropper which is trying to steal the classified message signal. The proposed scenario can be viable for a secondary safety task force working with a primary regiment, which wishes to transmit the confidential information to the commander while an eavesdropper is trying to intercept the classified information. In the analysis, two novel power allocation methods are considered by assuming perfect and limited feedback channels of the primary network, and for both methods, exact and asymptotic expressions of secrecy outage probability (SOP) are derived for N*Nakagami‐m fading channels which are used to model fading channels such as mobile‐to‐mobile/vehicle‐to‐vehicle communication systems where the nodes are moving into a rich scattering environment. We further verified our analytic results through Monte‐Carlo simulations. It is shown from the numerical results that the cascading degree of the channels has a worsening effect on the secrecy outage performance of the CRN systems.     

能量收集认知多跳中继网络中断性能分析及优化

针对能量收集认知无线网络中的多跳中继传输问题,该文构建了一种新的具有主网络干扰的功率信标(PB)辅助能量收集认知多跳中继网络模型,并提出单向传输方案。在干扰链路统计信道状态信息场景下,推导了次网络精确和渐近总中断概率闭合式。针对精确总中断概率表达式的复杂性和非凸性,采用自适应混沌粒子群优化(ACPSO)算法对次网络总中断性能进行优化。仿真结果表明,PB功率、干扰约束、次网络跳数、能量收集比率、主接收端数目和信道容量阈值等参数对中断性能影响显著,所提算法能快速和有效地对网络中断性能进行优化。     

Physical Layer Security for Wireless Powered Massive MIMO Decode and Forward Relay Systems with Hardware Impairments: Performance Analysis

In this paper, the issue of secrecy capacity of wireless powered massive MIMO dual hop relay system with a single antenna eavesdropper having non ideal hardware is addressed. The relay harvests energy in a proportionate manner and passes it to destination through beamforming with classical decode and forward relaying protocol. The relay has no channel state information (CSI) of passive eavesdropper but has CSI of the legitimate channel. The work presented in this paper focuses on the analysis of the difference in system performance with ideal and non ideal hardware, bounded by strict outage probability. The performance (in terms of secrecy outage capacity) is studied with hardware impairments (HWIs) defined for all network elements, i.e., source, relay, destination and passive eavesdropper. It is also observed that compared to ideal hardware, there is significant degradation in performance due to HWIs.

     

Security versus reliability analysis for multi-eavesdropper cooperation wireless networks with best relay

Physical-layer security could be used to effectively combat eavesdroppers and the transmission reliability of the main link could be improved.A wireless relay network with multiple both decode and forward eavesdroppers and relays were considered,in the presence of the link from source to destination.A best relay selection scheme based on multieavesdropper’s cooperation was proposed,and the outage probability and the intercept probability was deduced under both schemes without relay and with best relay.Then,the security and reliability influenced by different relay selection schemes were analyzed.The simulation results show that the achievable channel capacity at the destination node and the system outage probability are directly affected by different relay selection scheme.Lower system outage probability can be achieved by the proposed scheme,and the system outage probability and intercept probability are both decreased with the increase of the number of relays.The intercept probability increases with the increase of the number of eavesdroppers,which,however,can be reduced by increasing the number of relays to ensure the main link’s reliable transmission.