MF中继选择系统的物理层安全性能

针对合谋窃听场景下单天线多中继修改转发（MF）协作无线系统的安全性能较差问题,提出一种合谋窃听场景下联合源节点发送天线选择（TAS）和多中继选择的MF协作物理层安全系统,考虑最优的最大化主信道信噪比（SNR）和次优的最大化源节点-中继节点链路 SNR 两种中继选择方案,推导其安全中断概率（SOP）和遍历安全容量（ESC）的解析表达式。最优或次优中继选择的MF安全中继系统的SOP和ESC的数值计算结果与仿真结果相吻合,验证了上述理论分析的正确性;同时也表明源节点发射天线数和中继节点数越多、窃听节点数越少,最优或次优中继选择的MF安全中继系统的物理层安全性能越好。     

基于有限反馈的非可信中继系统的物理层安全性能分析

在基于有限反馈获得部分信道状态信息的条件下,研究了放大转发非可信中继系统的物理层安全传输技术.通过目的节点发送人工噪声干扰信息,使系统获得了正安全容量.推导了安全中断概率和传输中断概率的闭合表达式,分析了反馈比特数对系统安全性和可靠性的影响,进而提出了能同时兼顾系统安全性和可靠性的最优反馈比特数的自适应选择方案.     

多中继与多用户选择的中继系统安全性能分析

为了考察使用多中继选择与多用户选择的放大转发（AF）中继系统的物理层安全性能,推导了其在瑞利衰落信道上和联合发送天线选择/接收最大比合并天线分集下的非零安全容量概率和安全中断概率的精确表达式以及在高信噪比下的渐近安全中断概率解析表达式。AF中继系统的非零安全容量概率和安全中断概率的数值计算和仿真结果相吻合,验证了以上理论分析的正确性;分析结果表明,其安全分集增益为源节点发射天线数、最优中继节点接收天线数、中继节点数的三者乘积与最优中继节点发射天线数、最优用户接收天线数、用户数三者乘积之间的最小值,且与窃听信道无关。     

Nakagami信道下MIMO解码转发中继系统的安全性能分析

在协同自适应解码转发中继系统中,该文针对Nakagami-m衰落信道,研究了基于多天线低复杂度的机会式传输策略的物理层安全性能。为充分利用天线分集增益提升系统安全性能,发送节点均采用发送天线选择策略,接收节点均采用最大比合并策略。推导了系统安全中断概率的闭合表达式,并进一步提供了渐近性能分析,得到了系统的安全分集阶数。仿真结果验证了理论分析的正确性,并揭示了各系统参数对机会式传输方案的安全性能的影响。结果表明,通过增加合法节点的天线数和增大合法信道的Nakagami衰落信道参数可显著提升系统安全性能。     

多跳协同中继网络下物理层安全传输方案

针对多跳中继传输系统的信息安全传输问题,提出了一种基于全双工模式下多节点协作干扰(FD-MCJ)的物理层安全传输方案。该方案利用通信网络中的中继节点发送干扰信号恶化窃听节点的接收性能,同时中继节点根据信道状态信息(Channel State Information, CSI)自适应的选择两种情况下的安全传输方案。本文首先利用泊松点过程对窃听节点位置进行安全建模;然后,根据CSI可用程度,给出不同的安全传输具体方案,在考虑系统的跳数、天线间自干扰以及发射功率和干扰功率等因素下,推导FD-MCJ方案下系统保密中断概率的闭式解;最后,数值分析和蒙特卡洛仿真表明,理论推导的正确性以及多跳中继系统中采用全双工多节点协作干扰方案能够有效提升系统安全性能。      

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。     

基于协作干扰的全双工中继系统混合安全传输协议

针对全双工中继系统的安全问题,提出一种基于协作干扰的物理层安全混合传输协议.系统根据自身信道状态信息,自适应地选择基于中继节点与信源节点轮流发送干扰(RSCJ)协议或基于中继节点与目的节点轮流发送干扰(RDCJ)协议中安全容量相对较高的协议进行信息的传输.在全双工节点自干扰因素被抑制的条件下,给出了系统的传输协议选择策略,并理论推导了采用RSCJ或RDCJ传输协议下系统的安全中断概率表达式.仿真结果表明,利用所提的混合安全传输协议可以显著提高全双工中继系统的安全中断性能,与传统未利用协作干扰的传输机制相比,具有明显的安全性能优势.     

Underlay协同频谱共享系统中基于SDF-DZFB的物理层安全传输

协同中继传输不仅能改善认知用户的传输可靠性,而且也能增强认知用户物理层安全性。针对Underlay模式下多中继协同频谱共享认知无线网络,本文设计了基于选择译码转发和分布式迫零波束成形（SDF-DZFB）的物理层安全传输方案,其中,假设存在单个被动窃听节点窃听中继节点的发送信号,在认知用户发送端同时考虑峰值干扰温度约束和最大发射功率约束,中继和认知用户目的端都受到主用户干扰。在此情况下,分析了认知用户发送端分别到目的端（称为主链路）和到窃听节点（称为窃听链路）的等效信干噪比的统计特性,进而推导出系统安全中断概率性能的闭式表达式。为了揭示所提物理层安全传输方案的安全分集度性能,本文进一步分析了高信噪比条件下安全中断概率的渐近表达式。计算机仿真验证了本文的理论分析结果。      

多用户分集与能量受限非可信中继系统遍历安全性能分析

研究了一种能量受限的非可信中继与多用户分集技术相结合的两跳链路安全网络通信模型。为提升系统安全性能，本文采用混合时间-功率分配中继(time-power splitting-based relaying, TPSR)协议,并结合机会调度策略(opportunistic scheduling strategy, OSS)从多用户分集网络中选择一个最佳目的节点作为信息接收端。基于随机选择(random selection, RS)策略，该文中利用低复杂度的高斯Q函数分析系统的安全性能以及在协作中继上进行能量采集活动不中断的条件下推导了系统的遍历安全速率(ergodic secrecy rate, ESR)的近似闭合表达式。此外，将提出的OSS与RS通信方案下性能进行对比，证明本文所提出的OSS更适用于分布式多用户选择网络。      

NOMA系统中基于协作干扰的物理层安全方案

针对NOMA系统中的信息安全传输问题,提出基于协作干扰的物理层安全方案,该方案利用外部协作节点发送干扰信号恶化窃听者的接收性能。本文首先利用泊松点过程对协作节点和窃听者的位置进行安全建模,然后推导了随机协作干扰方案下系统保密中断概率的闭式解,但随机协作干扰方案会同时恶化合法用户的接收信号,性能有限,因此提出一种信道增益受限的协作干扰方案,该方案选择到近端用户和远端用户的瑞利信道因子均小于一定阈值的协作节点发送干扰信号,会对窃听者造成更严重的影响。仿真结果表明,在NOMA系统中采用受限的协作干扰方案能够有效提升系统安全性能。      

Secure Energy Harvesting Communications with Relay Selection over Nakagami-m Fading Channels

In this paper, an energy harvesting relay network over Nakagami-m fading is investigated. In the considered system, the power beacon can provide wireless energy for the source and relays which deploy time-switching-based radio frequency energy harvesting technique. Two relay selection schemes, namely partial relay selection and optimal relay selection, are proposed in order to enhance the system performance. In the former, the source only has the channel state information of the first hop, while in the latter it has the full knowledge of the channel state information. The eavesdropper is able to wiretap to the signal transmitted from the source and the relays. The exact closed-form expressions of secrecy outage probability are derived. The results show that optimal relay selection performs better than partial relay selection. With increasing number of relays, the considered system shows better performance. In addition, the energy harvesting duration has a significant effect on the secrecy outage probability.     

Cooperative Privacy Provisioning for Energy Harvesting Based Cognitive Multi-Relay Networks

In order to provide privacy provisioning for the secondary information,we propose an energy harvesting based secure transmission scheme for the cognitive multi-relay networks.In the proposed scheme,two secondary relays harvest energy to power the secondary transmitter and assist the secondary secure transmission without interfere the secondary transmission.Specifically,the proposed secure transmission policy is implemented into two phases.In the first phase,the secondary transmitter transmits the secrecy information and jamming signal through the power split method.After harvesting energy from a fraction of received radio-frequency signals,one secondary relay adopts the amplify-and-forward relay protocol to assist the secondary secure transmission and the other secondary relay just forwards the new designed jamming signal to protect the secondary privacy information and degrade the jamming interference at the secondary receiver.For the proposed scheme,we first analyze the average secrecy rate,the secondary secrecy outage probability,and the ergodic secrecy rate,and derive their closed-form expressions.Following the above results,we optimally allocate the transmission power such that the secrecy rate is maximized under the secrecy outage probability constraint.For the optimization problem,an AI based simulated annealing algorithm is proposed to allocate the transmit power.Numerical results are presented to validate the performance analytical results and show the performance superiority of the proposed scheme in terms of the average secrecy rate.     

Relay selection for secrecy connectivity in random wireless networks

In the paper, we study the problem of secure connectivity for colluding eavesdroppers using relay selection in random wireless networks, where the relay nodes and eavesdroppers are all randomly distributed according to two independent Poisson point process. The decode‐and‐forward and randomize‐and‐forward two relay strategies are considered, and a new metric is defined for best relay selection and random relay selection. We derive closed‐form expressions for the secrecy outage probability for the two relay strategies. In particular, the effect of power allocation ratio and the maximum ratio combing at the destination node on the secrecy outage probability is demonstrated for the decode‐and‐forward relay strategy. Numerical results illustrate the secrecy performance gains with collaborative transmit diversity. © 2016 The Authors. Wireless Communications and Mobile Computing Published by John Wiley & Sons Ltd.     

Secure communication via an energy-harvesting untrusted relay in the presence of an eavesdropper

This article studies a secure communication of a simultaneous wireless information and power transfer system in which an energy-constrained untrusted relay, which harvests energy from the wireless signals, helps the communication between the source and destination and is able to decode the source’s confidential signal. Additionally, the source’s confidential signal is also overheard by a passive eavesdropper. To create positive secrecy capacity, a destination-assisted jamming signal that is completely cancelled at the destination is adopted. Moreover, the jamming signal is also exploited as an additional energy source. To evaluate the secrecy performance, analytical expressions for the secrecy outage probability (SOP) and the average secrecy capacity are derived. Moreover, a high-power approximation for the SOP is presented. The accuracy of the analytical results is verified by Monte Carlo simulations. Numerical results provide valuable insights into the effect of various system parameters, such as the energy-harvesting efficiency, secrecy rate threshold, power-splitting ratio, transmit powers, and locations of the relay and eavesdropper, on the secrecy performance.     

Secrecy Performance of CCRN with an EHAF Relay under Source and Destination Jamming

In this paper, we investigate the secrecy performance of a cooperative cognitive radio network (CCRN) considering a single energy harvesting (EH) half‐duplex amplify and forward (AF) relay and an eavesdropper (EAV). Power is allocated to each node under cognitive constraints. Because of the absence of a direct wireless link, secondary source (SS) communicates with secondary destination (SD) in two time slots. The SD and the SS broadcast jamming signal to confuse the EAV in the first and in the second time slots, respectively. The relay harvests energy in the first time slot and amplifies and forwards the signal to SD in the second time slot. The EAV employs maximal ratio combining scheme to extract the information. We evaluate the performance in terms of secrecy outage probability (SOP) of the proposed CCRN. The approximate expression of SOP is obtained in integration form. Improvement in SOP is expected for the proposed CCRN because of the use of jamming signals. The secrecy performance of CCRN improves with increase in primary transmit power, peak transmit power of secondary nodes, channel mean power, and energy conversion efficiency but degrades with increase in threshold outage rate of primary receiver and threshold secrecy rate. A MATLAB‐based simulation framework has been developed to validate the analytical work.     

Secrecy outage analysis in a hybrid cognitive relay network with energy harvesting

In this paper, we investigate the physical layer security of a hybrid cognitive relay network using an energy harvesting relay in presence of an eavesdropper. In the hybrid scheme, a secondary user (SU) as well as a cognitive relay works either in underlay or in overlay mode. In underlay, the transmit power of the SU as well as the relay is limited by the maximum acceptable interference at primary user (PU) receiver as required by an outage constraint of PU, a quality of service for PU. The secondary network consists of a decode and forward relay that harvests energy from radio frequency signal of secondary transmitter as well as PU transmitter to assist the SU in forwarding the information signal to the destination. A time switching relaying protocol is used at the relay. We evaluate the secrecy outage probability of secondary relay network assuming that channel state information of the interfering links from both the SU and relay transmitter to PU receiver is imperfect. Our results reveal the impact of imperfect channel state information, energy harvesting time, tolerable interference threshold, and PU outage constraint on the secrecy outage probability of SU.     

Physical layer security performance analysis of multi-antenna full-duplex relay aided heterogeneous cellular network

To alleviate the spectrum shortage problem and security threats in heterogeneous network (HetNet),multi-antenna full-duplex relay was introduced for communication between femto base station (FBS) and legitimate user.With the aid of multi-antenna full-duplex relay in FBS network,the secrecy performance of HetNets could be improved.Under a stochastic geometry framework,the fundamental analysis model to evaluate the secrecy performance in multi-antenna full-duplex relay aided HetNet was set up.To be specific,the exact expressions for the secrecy outage probability of the typical user,serving relays and HetNet were derived respectively.Then,based on the theoretical analyses and simulation results,the influences of transmit power and antenna number of both macro base station and FBS on secrecy performance in HetNet were examined.Finally,the results show that introducing multi-antenna full-duplex relay for FBS networks improves the secrecy performance of HetNet.     

Outage Performance of Energy Harvesting DF Relaying NOMA Networks

In this paper, we investigate energy harvesting decode-and-forward relaying non-orthogonal multiple access (NOMA) networks. We study two cases of single relay and multiple relays with partial relay selection strategy. Specifically, one source node wishes to transmit two symbols to two respective destinations directly and via the help of one selected intermediate energy constraint relay node, and the NOMA technique is applied in the transmission of both hops (from source to relay and from relay to destinations). For performance evaluation, we derive the closed-form expressions for the outage probability (OP) at D ₁ and D ₂ with both cases of single and multiple relays. Our analysis is substantiated via Monte Carlo simulation. The effect of several parameters, such as power allocation factors in both transmissions in two hops, power splitting ratio, energy harvesting efficiency, and the location of relay nodes to the outage performances at the two destinations is investigated.