相关衰落信道下的安全协作系统及中断性能

基于相关的瑞利衰落信道,研究安全协作系统的安全中断性能。假定发送端知道全部信道的信道状态信息,系统中存在单个窃听节点以及多个进行协作的中继节点,某个中继节点被选择作为干扰者来发送干扰信号,合法信道与干扰节点到目的节点的信道相关,窃听信道与干扰节点到窃听节点的信道也相关。在此类协作场景中,分析了信道相关性对安全协作系统安全性能的影响,获得了安全中断概率表达式。数值结果表明信道相关对安全协作系统的安全性能存在显著影响。     

Physical layer security of underlay cognitive radio using maximal ratio combining

We investigate the secrecy outage performance of maximal ratio combining (MRC) in cognitive radio networks over Rayleigh fading channels. In a single-input multiple-output wiretap system, we consider a secondary user (SU-TX) that transmits confidential messages to another secondary user (SU-RX) equipped with M (M ≥ 1) antennas where the MRC technique is adopted to improve its received signal-to-noise ratio. Meanwhile, an eavesdropper equipped with N (N ≥ 1) antennas adopts the MRC scheme to overhear the information between SU-TX and SU-RX. SU-TX adopts the underlay strategy to guarantee the service quality of the primary user without spectrum sensing. We derive the closed-form expressions for an exact and asymptotic secrecy outage probability.     

Secrecy performance analysis of single-input multiple-output generalized-<Emphasis Type="Italic">K</Emphasis> fading channels

In this paper, the transmission of confidential messages through single-input multiple-output (SIMO) independent and identically generalized-K (K_G) fading channels is considered, where the eavesdropper overhears the transmission from the transmitter to the receiver. Both the receiver and the eavesdropper are equipped with multiple antennas, and both active and passive eavesdroppings are considered where the channel state information of the eavesdropper’s channel is or is not available at the transmitter. The secrecy performance of SIMO K_G systems is investigated. Analytical expressions for secrecy outage probability and average secrecy capacity of SIMO systems are derived via two different methods, in which K_G distribution is approximated by the Gamma and mixture Gamma distributions, respectively. Numerical results are presented and verified via the Monte-Carlo simulation.     

Physical layer security via maximal ratio combining and relay selection over Rayleigh fading channels

In this paper, the impact of both maximal ratio combining (MRC) and relay selection on the physical layer security in wireless communication systems is investigated by analyzing critical issues such as the probability characteristics of the legitimate receiver (Bob) and malicious eavesdropper (Eve)’s end-to-end signal-to-noise ratio (SNR), the secrecy outage probability and the average secrecy channel capacity over Rayleigh fading Channel, etc. Unlike the conventional physical layer security schemes, we assume that Bob receives its data from both the relay and the source via cooperative relay, provided that MRC is employed at the receiver. Particularly, compared to the conventional MRC methods, the proposed method is capable of achieving a higher spatial diversity order by performing relay selection, as validated by performing the theoretical analysis as well as numerical simulation. Furthermore, the closed-form expressions in terms of secrecy outage probability and average secrecy capacity are all consistent with the numerical results. Finally, the proposed scheme may be substantially affected by a number of parameters such as the number of relays, the SNR of links and the ratio of main-to-eavesdropper ratio (MER) λ_ME.     

Secrecy outage analysis for underlay cognitive radio networks over correlated channels

This paper investigates the secrecy outage performance of underlay cognitive radio networks, in which a source in a secondary system transmits its confidential information to a legitimate destination in the presence of an eavesdropper. Specifically, the main (the source-to-destination) and eavesdropping (the sourceto- eavesdropper) channels are assumed to be correlated. Moreover, it is also assumed that the main channel and the channel from the source to the primary user’s receiver are correlated. Tight closed-form analytical expression for secrecy outage probability and the closed-form analytical expression for the probability of non-zero secrecy capacity are derived and validated by simulation results when the interference temperature limit is comparably large.     

信道预测天线选择的空时分组码物理层安全增强

针对延时发射天线选择(TASD)/正交空时分组码(OSTBC)无线通信系统,基于最小均方误差(MMSE)信道预测器,提出一种系统物理层安全增强方案。将MMSE信道预测方案应用于TASD/OSTBC无线通信系统,构成信道预测发射天线选择(TASP)/OSTBC无线通信系统,并对其推导瑞利块衰落信道上安全中断概率、非零安全容量概率以及渐近安全中断概率的解析表达式。在此基础上,分析主信道收发天线数、窃听者天线数和信道的归一化延时等参数对系统物理层安全性能的影响。数值计算和仿真结果表明,采用TASP可以提高OSTBC编码无线通信系统的物理层安全性能。     

基于最佳中继选择的认知AF系统性能分析

针对中继通信中的放大转发协议,提出了一个基于最佳中继选择方案的双跳认知协作通信系统。该系统的频谱共享环境由一个主接收用户,一个次级信源,[K]个次级中继和一个次级信宿组成。并在独立非同一分布的瑞利衰落环境下对该认知协作通信系统的中断性能进行了分析,推导出了中断概率的准确闭合表达式。利用蒙特卡罗仿真实验证实了分析结果的正确性。理论分析和仿真结果都表明,分析所运用的方法降低了系统的中断概率,提高了遍历容量,从而有效地改善了系统的性能。     

信道估计误差与同道干扰下的双向中继系统性能分析

分别在瑞利衰落 环境和瑞利 莱斯混合衰落环境下,研究了双向中继系统在同时受到信道估计误差和同道干扰影响下的中断概率性能。首先,给出了系统模型以及系统协议;然后,基于得到的接收端信干噪比表达式,分别推导了双向中继系统在单一瑞利衰落环境和瑞利 莱斯混合衰落环境下的中断概率表达式;最后,分析了双向中继系统受信道估计误差和同道干扰影响时的最佳中继位置选择,并得出了最佳中继位置的闭式表达式。数值仿真验证了所推导的中断概率表达式以及最佳中继位置表达式的正确性,揭示了信道估计误差和同道干扰对系统性能的影响,表明当信道估计质量阶数小于1时性能将明显下降,当衰落因子增大时性能将得到提高。     

协作通信的中继选择策略性能研究

在解码转发协议的基础上,研究了全选中继策略和机会中继选择策略的中断概率性能,推导了瑞利衰落下的两种策略的中断概率精确闭式结果,给出了高信噪比时的中断概率近似表达式.通过理论分析和数值仿真结果得出:在信噪比足够高或在中继-目的信道性能优于源-中继的信道性能的情况下,这两种策略具有相同的中断概率性能;源-中继的信道性能比中继-目的节点的信道性能越好,全选中继策略的性能越优于机会中继选择策略的中断概率性能.     

多用户环境下的认知协作通信系统性能分析

在存在多个主用户的环境下, 提出一种新型的两跳式协作通信系统, 并对系统的性能进行了分析。该系统在信宿处有多个次级用户接收机, 并且采用信道参数最优的方式进行用户选择。在瑞利衰落信道下, 对提出的协作通信系统的中断概率进行了研究, 得出了中断概率的闭合表达式及在高信噪比时的渐进表达式。最后通过计算机仿真验证了其有效性, 分析结果显示在多用户条件下系统的整体性能得到明显提高。     

一种提高OFDM系统安全传输的载波功率分配算法

现有的OFDM安全传输技术无法满足无线通信系统对安全性能的需求,针对这一问题,提出了一种旨在提高OFDM系统安全传输速率的载波功率分配算法。考虑OFDM各载波信道存在的衰落差异性,基于OFDM窃听信道模型推导出窃听端与授权接收端平均信噪比不同的系统安全传输速率;在总功率受限的条件下,以安全传输速率最大化为目标,利用K-T条件对各载波功率进行优化分配,从而提高OFDM系统安全传输性能。仿真结果表明,当选用128个载波时,优化分配的安全传输速率比平均分配的安全传输速率最多可以提升6.109 bit/s/Hz,并且随着载波数的不断增加,安全传输速率的提升也越来越明显。     

节点位置对窃听信道安全容量的影响

随着无线通信技术的不断发展,无线通信中的安全问题已成为制约其发展的重要因素。文中基于香农信息论,从安全区域的角度分析了加入协作干扰后瑞利衰落窃听信道模型的安全性能,并且对窃听节点与协作干扰节点的位置变化与系统安全容量的关系进行了研究,然后在瑞利衰落信道模型下基于地理位置的变化对遍历保密容量进行了数值仿真。结果表明引入协作干扰节点可以提升系统安全容量,且适当增加协作者个数、调整协作者位置以及合理的功率分配都可以增强通信系统的安全性。     

多天线认知协作通信系统的性能分析

在多个主用户同时存在的情境下,提出了一种新的两跳认知协作通信系统,并对该系统进行了性能分析。该系统的信源和中继均只具有单个天线,而在信宿处配置了多根接收天线并使用了最大比合并技术来进行信号的接收。此外,对该认知协作通信系统在瑞利衰落信道下的中断概率性能进行了研究,推导得到了中断概率的准确闭合表达式,以及在高信噪比时的渐进表达式。通过利用计算机仿真验证了理论分析的正确性。     

Physical layer security in multi-antenna cognitive heterogeneous cellular networks: a unified secrecy performance analysis

Cognitive heterogeneous cellular networks (CHCNs) are emerging as a promising approach to next-generation wireless communications owing to their seamless coverage and high network throughput. In this paper, we describe our reliance on multi-antenna technology and a secrecy transmission protocol to ensure the reliability and security of downlink underlay CHCNs. First, we introduce a two-tier CHCN model using a stochastic geometry framework, and derive the probability distribution of the indicator function for a secrecy transmission scheme. We then investigate the connection outage probability, secrecy outage probability (SOP), and transmission SOP of both primary and cognitive users under a secrecy guard scheme and a threshold-based scheme. Furthermore, we reveal some insights into the secrecy performance by properly setting the predetermined access threshold and the radius of detection region for the secrecy transmission scheme. Finally, simulation results are provided to show the influence of the antenna system, eavesdropper density, predetermined access threshold, and radius of the detection region on the reliability and security performance of a CHCN.     

Classical-quantum arbitrarily varying wiretap channel: common randomness assisted code and continuity

We determine the secrecy capacities under common randomness assisted coding of arbitrarily varying classical-quantum wiretap channels. Furthermore, we determine the secrecy capacity of a mixed channel model which is compound from the sender to the legitimate receiver and varies arbitrarily from the sender to the eavesdropper. We examine when the secrecy capacity is a continuous function of the system parameters as an application and show that resources, e.g., having access to a perfect copy of the outcome of a random experiment, can guarantee continuity of the capacity function of arbitrarily varying classical-quantum wiretap channels.     

Capacity of orthogonal space-time block codes in MISO fading channels with co-channel interference and noise

Orthogonal space-time block codes(OSTBCs) are an efficient mean in order to exploit the diversity offered by the wireless multiple-input multiple-output(MIMO) channel. This paper considers capacity problems of OSTBCs over spatially correlated multiple-input single-out(MISO) Rayleigh fading channels in the presence of spatially correlated Rayleigh co-channel interference and additive Gaussian noise,and derives exact expressions of the ergodic capacity and outage probability(capacity distribution) for such OS...     

On the performance analysis of SIR-based SSC diversity over correlated α-μ fading channels

In this paper, an approach to the performance analysis of dual-branch switch-and-stay combining (SSC) diversity receiver, operating over correlated α-μ fading channels in the presence of co-channel interference (CCI), is presented. Very useful novel infinite series expressions are obtained for the probability density function (PDF) and cumulative distribution function (CDF) of the SSC output signal-to-interference ratio (SIR). Capitalizing on these, performance analysis is performed based on standard criterion measures, such as the outage probability (OP) and average bit error probability (ABEP). Obtained results are graphically presented to show the effects of various parameters such as the fading severity, propagation environment non-linearity and level of correlation on the overall system’s performance.     

基于独立非同分布广义K信道的OSTBC-MIMO系统及性能

针对独立非同分布（i.n.i.d.）广义K衰落信道中的正交空时分组编码多输入多输出（OSTBC-MIMO）系统性能问题,建立了采用M-QAM调制的OSTBC-MIMO系统在i.n.i.d广义K衰落信道中的系统模型。利用接收端等效信噪比（SNR）可以近似为两个由多个独立伽马随机变量之和构成的随机变量的乘积这一关系,推导出近似等效信噪比的概率密度函数表达式,继而推导得到平均符号差错概率、中断概率和容量的闭式。仿真结果表明：除波形参数m外,k取任意不同正整数值也会对系统性能产生重要的影响,OSTBC-MIMO系统在i.n.i.d.广义K衰落信道中的性能与在独立同分布（i.i.d.）广义K衰落信道中的性能存在显著差别。     

基于无线能量采集的多跳网络安全传输中的路径选择

针对具有无线能量采集技术的多跳传输网络,提出了全双工中继网络在有多个窃听者和多个功率节点场景下进行多跳多路径传输时的路径选择问题。首先,所提系统模型在有多个窃听者和功率节点的场景下进行信息传输,将源发射端和接收端之间的最佳路径作为数据传输路径。然后,为了增强系统性能,中继节点对功率节点发出的射频信号进行能量采集并利用所获能量来进行下一跳的数据传输。最后,推导出了所提路径选择方法在瑞利衰落信道下端到端中断概率的精确表达式,蒙特卡洛仿真和理论分析曲线拟合较好,说明了理论推导的正确性,以及所提方法具有性能上的优越性。     

Variable energy adaptation for asynchronous CDMA communications over slowly fading channels

In this paper, a detailed theoretical analysis of variable energy adaptation in an asynchronous code division multiple access (A-CDMA) system is discussed. Rayleigh and Rician frequency-selective slowly fading channels are considered. The receiver, capable of measuring the received signal energy-to-noise ratio, provides the transmitter with the necessary signal-to-noise ratio measurement to control the transmitter energy through a noise-free feedback channel. System parameters such as fading margin and mean transmitter energy gain are calculated for both Rayleigh and Rician fading channels as a function of the probability of error specification and the probability of unsatisfactory operation.