非理想CSI下全双工双向中继网络安全性能研究

针对目前物理层安全研究大多未考虑信道估计误差对安全性能的影响,研究基于非理想信道状态信息（Channel State Information,CSI）的全双工双向中继网络安全性能。假设系统中用户之间没有直连链路,且无法获取CSI;采用最优中继选择方案,选取最优中继将信号进行解码转发至目的端;根据最大最小原则推导出系统安全容量和保密中断概率（Secrecy Outage Probability,SOP）的表达式,进一步分析影响系统保密性能的主要因素,并对比全双工与半双工系统性能的差异。仿真结果表明,当中继节点处在用户间的中点位置时,系统保密性能最好;同时,减小信道估计误差、窃听链路的平均信噪比及剩余自干扰能够有效降低系统SOP,适当地增加中继数目可以获得更好的安全性能。     

非对称双向多中继系统机会式网络编码中断概率分析

首先建立了非对称双向多中继系统数学模型,采用机会中继策略,推导出了该模型在译码转发方式下采用网络编码时的中断概率表达式, Monte Carlo仿真和理论值非常吻合,充分验证了该表达式的正确性。其次分析了不同中继节点位置,不同中继节点个数和不同功率分配因子等情况下的系统中断性能,揭示了功率分配因子与中继节点个数和位置以及系统总功率的内在关系。仿真结果表明,在非对称双向多中继系统中同时采用网络编码和机会中继时,功率分配因子取值为0.6时可获得最佳的系统中断性能,并指出在研究中断概率问题时,中继节点位置是一个不可忽略的因素。     

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.     

基于中继联合优化选择的物理层安全方案

针对认知无线电(CR)网络中的安全传输问题,提出基于传输中继和干扰中继联合优化选择的物理层安全方案。在主用户网络和次用户网络共存的环境中,通过优化选取协作传输中继和协作干扰中继实现信息的安全传输,并分析推导出瑞利衰落环境下该方案保密中断概率的闭式表达式。仿真结果表明,在不同参数场景下,该方案均可实现较低的保密中断概率,提升CR网络的信息传输安全性能。     

混合信道下译码转发中继系统性能研究

针对中继协作系统,研究瑞利信道和Nakagami-◢m◣信道的混合信道下解码转发（decode-and-forward）中继系统性能。结合信息传输过程中可能发生的数据平均误包率,推导出以源节点和中继节点的调制等级为设计变量的双中继端到端频谱效率表达式以及系统稳定性表达式,同时还分析了不同信道参数◢m◣对于链路频谱效率以及系统稳定性的影响,对表达式进行高阶变量推导演变可得出多中继频谱效率表达式及系统稳定性表达式,最后通过仿真验证了端到端表达式所得结果优于传统的自适应算法。     

干扰影响下无线携能通信双向中继系统中断性能分析

在无线携能通信双向中继系统中,大量无线信息发射源会导致系统性能受到同频干扰的影响。以基于射频能量收集的双向中继网络为研究对象,结合功率分离能量收集和解码转发信息转发方式,建立中继和接收端分别受到多个干扰源影响下的无线携能通信双向中继通信系统传输模型,在3个时隙信息能量同传的传输帧结构下,得到系统端到端信干噪比,并分析该传输模型下的中断性能。利用数学推导得出该系统在瑞利信道环境下的端到端信干噪比的累积分布函数闭式解,在此基础上求解中断概率闭式值,并通过数值仿真探讨干扰源个数、干扰功率以及功率分割比对系统中断概率的影响。仿真结果表明,所求中断概率闭式表达式与蒙特卡洛仿真中断概率曲线完全吻合,双向中继传输能有效降低系统中断概率,其中干扰源个数越多、干扰功率越大对系统的中断性能影响越大,但不影响系统的分集度,并且存在一个最优功率分割比值可使系统的中断性能达到最优,从而提升整个系统的传输性能。     

双向中继系统中断概率下界优化及分集增益

主要研究了瑞利衰落信道下基于放大转发策略的双向中继系统的中断性能及分集性能。首先利用信源节点信噪比间的关系和调和不等式对信噪比的范围进行优化,得到新的中断概率下界,仿真结果表明Monte Carlo仿真得到的中断概率接近新得到的中断概率下界;同时证明了多中继存在时,基于最大最小互信息准则的双向中继系统仍然取得全分集增益且能够优化中断概率下界。     

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。     

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。     

基于非理想CSI的全双工双向中继系统保密中断概率性能研究

研究基于译码转发的全双工中继系统的物理层安全问题。假设系统模型中窃听者与合法用户以及中继之间存在直接链路,考虑在合法用户和中继之间的信道状态信息（channel state information,CSI）是非理想的情况下,通过分析信道估计误差、窃听信道的平均信噪比和残余自干扰对中继系统物理层安全的影响,推导出每个节点端到端瞬时信干噪比和非理想CSI下的保密中断概率表达式。仿真结果表明,信道估计误差、窃听信道的平均信噪比和残余自干扰越小,系统保密中断概率越小,系统安全性能越高;在高信噪比时,残余自干扰对保密中断概率的影响可以忽略不计;同时,全双工中继方案优于传统的半双工中继方案。     

Performance analysis of ad-hoc routing in heterogeneous clustered multi-hop wireless networks

This paper analyzes the performance of clustered decode-and-forward multi-hop relaying (CDFMR) wireless Rayleigh fading networks, and sheds light on their design principles for energy and spectral efficiency. The focus is on a general performance analysis (over all SNR range) of heterogeneous wireless networks with possibly different numbers of relays in clusters of various separations. For clustered multi-hop relaying systems, hop-by-hop routing is known as an efficient decentralized routing algorithm which selects the best relay node in each hop using local channel state information. In this article, we combine hop-by-hop routing and cooperative diversity in CDFMR systems, and we derive (i) a closed-form expression for the probability distribution of the end-to-end SNR at the destination node; (ii) the system symbol error rate (SER) performance for a wide class of modulation schemes; and (iii) exact analytical expressions for the system ergodic capacity, the outage probability and the achievable probability of the SNR (power) gain. We also provide simple analytical asymptotic expressions for SER and the outage probability in high SNR regime. Numerical results are provided to validate the correctness of the presented analyses.     

Transmission scheme and performance analysis for decode-and-forward MIMO two-way relay systems

In decode-and-forward (DF) MIMO two-way relay systems, the transmission schemes are designed and the closed-form expressions for the outage probability and average symbol error rate (ASER) of the twoway relay system are derived based on two different scenarios of channel state information (CSI). For perfect CSI, the maximum-ratio-transmission and combining (MRT-MRC) technique is applied to design the beamforming and combining vectors. Without perfect CSI, the transmission scheme with limited feedback is designed, and the analytical results are verified through two kinds of codebooks, i.e., random vector quantization and Grassmann. The simulation results show that, the proposed transmission schemes for the two-way relay system can outperform other transmission schemes in the performance of outage probability and ASER, and the accuracy of the derived closed-form expressions is also verified by the numerical simulations.     

基于天线选择的全双工中继干扰抑制

在全双工中继协作通信系统中,中继发送端和接收端之间的干扰严重影响了系统的传输性能,因此干扰抑制是全双工模式下的关键问题。与引入权重矩阵的抑制方法不同,介绍了一种在中继发送端和接收端同时进行天线选择的干扰抑制方法。在多天线中继衰落信道系统中,基于最小化干扰信道的信道容量准则,中继发送端和接收端均选择合适的天线子集。在该抑制方法的基础上,理论分析了系统信道容量的闭式表达。仿真结果表明,天线选择方案改善了系统的信道容量和误码率性能,干扰抑制效果明显,同时降低了系统的复杂性。     

Diversity order of multiuser two-way relay networks with beamforming over Nakagami-m fading channels

The diversity performance of multiuser two-way relay networks is investigated over Nakagami-m fading channels.We consider an amplify-and-forward relay network with beamforming at the base station and all the mobile stations,and derive closed-form lower and upper bounds on the outage probabilities of two unidirectional links,respectively.Moreover,the exact expression for the diversity order and the asymptotic expressions for the outage probabilities of two unidirectional links are given too.Finally,simulatio...     

Robust power allocation algorithm for analog network coding with imperfect CSI

Power allocation promises significant benefits in wireless networks. However, these benefits depend on knowledge of the channel state information （CSI）, which is hardly perfect. Therefore, robust algorithms that take into account such CSI uncertainties play an important role in the design of practical systems. In this paper, we formulate the power allocation problem as the maximum individual outage probability minimization subject to total power consumption for analog network coding （ANC） protocol of a two-way relay system. We show that these problems can be cast as convex optimization problems. Non-robust power allocation algorithm is first developed under the ideal assumption of perfect CSI. Then we introduce robust optimization methodology that accounts for the imperfect CSI. We show that ignoring CSI uncertainties in our designs can lead to drastic performance degradation. On the other hand, the proposed robust power allocation provides significant performance gain over non-robust power allocation and uniform power allocation in terms of overall system outage probability over a wide range of channel estimation errors. This work highlights the importance of the proposed robust algorithm in realistic two-way relaying networks.     

Traffic-information-utilized low-complexity relay selection for two-way AF relaying networks

This paper investigates a two-way amplify-and-forward multiple relaying network (TWMR-AF) and presents a novel relay selection scheme, which is appropriate for different traffic patterns and has very low implementation complexity, rendering it very attractive for practical systems. Assuming the TWMR-AF over Nakagami-m fading, the approximate expression of the overall outage probability is derived, and the diversity and code gains are then obtained. The analytical results indicate that the proposed policy achieves better outage performance than the traditional max-min relay selection scheme, as validated by the simulation results.     

机会中继协同通信系统在Nakagami-m衰落信道中的折中性能分析及系统优化

针对外部窃听者对多中继协同通信系统中信息传输带来的安全威胁,提出一种由中继节点在转发信息的同时发送人工干扰信号的协同安全传输方案,并对该方案在Nakagami-m衰落信道中的安全性能进行了分析,推导出了用于评估机会中继系统可靠性的中断概率和安全性截获概率的闭式表达式,并在此基础上从可靠性和安全性两方面对系统的折中性能进行了讨论。通过仿真,验证了推导的正确性,明确了中继个数对系统折中性能的影响。最后,为进一步提高系统折中性能,讨论了系统中人工干扰信号与通信信号间的功率分配问题,并通过仿真得到了能使系统折中性能达到最优的功率分配因子。