面向物理层安全的一种打孔极化编码方法

为了解决物理层安全编码中安全性和可靠性之间的矛盾和提高保密速率,该文提出一种基于打孔极化码的安全编码方法。根据信道极化理论,该方法将私密信息位映射到合法者正常接收而窃听者无法译码的特定逻辑信道输入位,保证私密信息可靠且安全传输。然后,通过分析极化码的校验关系树,利用3个参数表征输出节点对私密信息位的影响,再按照影响程度大小确定打孔位置。理论分析与仿真结果表明,该方法保证私密信息传输安全性和可靠性的同时,提高了私密信息传输的有效性。     

利用信道衰落幅度差异隐藏私密信息的物理层安全编码方法

针对基于码字结构的物理层安全编码方法安全间隙较大的问题,首先证明了低密度奇偶校验码中私密信息节点传输时的信道衰落幅度越小越有利于该节点的正确译码;然后选取合法信道衰落幅度最小的位置隐藏私密信息,形成有利于合法接收者译码的条件;再结合私密信息置乱将译码残余比特错误扩散到整个码字中,进一步提高窃听者对私密信息的译码错误概率。仿真结果表明,该方法的安全间隙比直接传输和仅私密信息置乱的方法分别缩小了23.5dB和4.5dB。      

采用网络编码的双向中继信道中软信息的传输方法

采用格栅编码量化(TCQ)这一信源编码方法结合格栅编码调制(TCM)技术,解决了双向中继信道中软信息的传输问题。仿真表明,在衰落信道下,该方法性能上优于传统的译码转发和放大转发的网络编码方法。该方法应用于双向中继信道并在有限带宽的情况下可获得接近理想信道的链路性能。该方法为软信息网络编码走向实用提供了一种有效的思路。     

窃听环境下AF中继选择与功率分配的研究

传统的最佳中继选择方案仅参考了合法用户的信道状态信息,在实际的通信系统中由于存在窃听用户而无法保证信息的可靠传输。现有的最佳中继选择方案将窃听用户的信道状态信息纳入考虑后,系统的安全性能得到了一定改善,但是依然采用的是等功率分配。针对放大转发协议,本文在现有最佳中继选择方案的基础上,以降低系统安全中断概率为目标,在系统总功率受限的前提下,根据源节点和中继节点以及中继节点和目的节点间的信道参数引出功率分配因子,对源节点和中继节点间的功率进行适当分配。通过仿真对比,可以发现功率分配能够降低系统的安全中断概率,从而改善系统的安全性能。      

不对称速率传输中网络编码与信道编码的联合设计

本文针对双向中继信道中不对称速率传输的情况进行了研究。在实际双向中继信道的通信传输中,由于信道质量,发射功率,业务需求等条件的不对称,双向信道的传输速率往往也是不对称的。本文提出了一种称为子集编码的方案,将调制、物理层网络编码、信道编码联合起来设计,使得较差信道的信道编码码字为较好信道的子集,这样中继节点可以利用信道编码的线性性质对接收到的叠加信号直接进行译码,从而使译码复杂度降低50%;同时,较好信道使用高阶调制,较差信道使用低阶调制,利用较好信道提高了系统的传输速率。仿真结果表明,与对称速率传输相比,本文提出的方案在提高系统有效性的同时,又保证了系统的可靠性。      

双LT码防窃听方案设计

针对传统LT码在窃听信道中窃听者截获效率较高的问题,提出一种双LT码编码的防窃听方案.该方案在传统LT编码的基础上,将第一次LT编码得到的部分码字作为第二次LT编码的信源再次进行LT编码,推迟接收者译码开始时间,致使合法接收者先于窃听者译码概率增加,窃听者无法继续接收LT码并对所接收到的LT符号进行译码,进而使其截获效...     

基于Turbo码的非理想中继协作性能研究

基于Turbo码的非理想中继信道协作方式是在加性高斯白噪声(AWGN)的环境下提出的一种协作通信方式。源节点将编码并调制后的信息分别传送给中继节点和目的节点,中继节点对接收到的码字进行译码、传送,目的节点接收2路不同的信号(一路是来自源节点未经过交织的信息比特和校验比特,另一路是来自中继信道经过交织后来的校验比特)并采用联合迭代的译码方式对其进行译码。仿真结果表明,同等条件下,基于Turbo码的非理想中继信道协作方式在纠错方面的性能远胜于点对点的Turbo码非协作方式。     

不对称速率双向中继传输策略研究

在实际双向中继信道的通信传输中,由于信道质量,发射功率,业务需求等条件的不对称,双向信道的传输速率往往也是不对称的。该文针对双向中继信道中不对称速率传输的情况进行了研究,基于物理层网络编码,提出两种不对称传输的方案。第1种方案采用级联信道编码;第2种方案采用子集编码和子集调制。这样设计使得中继节点对接收到的叠加信号只需一次译码就可以直接解出信息比特的异或,从而降低了译码复杂度。仿真结果表明,结合信道编码的不对称传输设计,在提高系统有效性的同时,进一步降低了误比特率,保证了系统的可靠性。     

协作通信技术在恶劣信道条件下的应用研究

为了在信道状况较差时仍能采用编码协作技术,提出了一种有效混合编码协作方法.以两用户为例,在两次发送时隙都采用QPSK调制,并采用LDPC码的混合自动重传(HARQ)方法,当第一时隙传输数据不能被正确译码时,源节点将重新传送数据,中继节点将接收到的数据联合上一次接收的数据进行联合译码.当数据重传后仍不能被正确译码时,中继节点将采用放大转发方式传输第二时隙的数据,此时转为放大转发模式进行协同通信,通过性能分析和仿真结果表明,当协作用户间信道状况较差时,与非协作和普通编码协作方式相比,所提的协作方法仍能获得一定的分集增益.     

多载波系统随机子载波加权的物理层加密算法

针对多载波传输系统中,基于载波资源分配算法在窃听者信道质量优于合法用户的条件下无法实现安全传输的问题,建立了OFDM系统安全传输模型并在物理层提出了一种随机子载波加权的加密算法。该算法将合法通信双方的信道状态信息作为区分不同用户的唯一特征,并以此在发端为每个子载波数据设置随机加权因子扰乱窃听用户接收的信号,而合法用户能够通过发送参考解调算法恢复数据,仿真结果表明,发端采用该算法进行加密后,合法用户的误比特率随信噪比的增加迅速下降,而窃听用户误比特率始终为50%,系统具有一定的保密传输速率,有效实现了信息的安全传输。     

Decode and forward polar coding for Half-duplex two-relay channels based on multilevel construction

Polar codes represent an emerging class of error-correcting codes with power to approach the capacity of the physically degraded relay channel and relevant coding schemes have been proposed in the literature. This paper aims to design new cooperative decode-and-forward (DF) polar coding schemes for half-duplex two-relay channel based on the Plotkin’s construction illustrating their performances gain. In these schemes, we consider the use of time-division process in transmission. The source node transmits its polar-coded information to both relays and the destination nodes during the first time slot. Each relay node receives the data from the source and processes it using the DF protocol. For the second transmission period, each relay first decodes the source signal then after reconstruction of the information reduction matrix based on the multilevel characteristics of polar codes, the extracted data at each relay are recoded using another polar code and transmitted to the destination. At destination node, the signals received from each relay and source nodes are processed by using multi-joint successive cancellation decoding for retrieving the original information bits. We demonstrate via simulation results that by carefully constructed polarisation matrix at each relay node, we can achieve the theoretical capacity in the half-duplex relay channel.     

Chaotic sequence based polar code encrypted scheme in negative secrecy capacity case

A chaos based encrypted polar coding scheme,which could be applied to the negative secrecy capacity case,was proposed.Chaotic sequences were employed to encrypt the information bits and fill the frozen bits.And multi-block polar coding structure was also employed in the proposed scheme.The proposed scheme was featured as lower complexity and higher secrecy transmission rate.Corresponding mathematical analysis had been performed in terms of the error probability,security and transmission rate.The result reveals that the proposed scheme can achieve reliability,security in negative secrecy capacity case.What’s more,it has relatively low complexity and high secrecy transmission rate compared with the existing schemes.     

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.     

过时信道状态信息下的机会式中继选择系统的安全性能分析

在 Nakagami m衰落信道下,目的端和窃听者采用最大比合并策略,本文研究了在机会式自适应解码转发中继选择安全协作系统中的安全性能。由于实际信道中的反馈延迟,最优的合法中继选择基于合法信道反馈的过时信道状态信息。为了评价机会式中继选择在改善安全性能上的表现,分别推导了准确的正安全容量概率和准确的安全中断概率闭合表达式。此外,针对两种不同情况, 推导了形式简单的渐近表达式,并明确给出安全分集阶数和安全阵列增益。理论分析和数值仿真表明,增加中继个数和目的节点的天线数能够改善安全中断概率的性能表现,且在信道状态信息过时的条件下,系统的安全分集阶数与中继数无关。      

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.     

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。     

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.     

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.     

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.