共查询到19条相似文献,搜索用时 46 毫秒
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本文研究了高斯MISO窃听信道的可达保密速率问题.系统模型包括一个发送者,一个接收者和一个窃听者.发送者将发送功率分成两部分,一部分功率发送信号,一部分功率发送人工干扰信号.推导出了采用人工干扰时的系统可达保密速率公式,并通过优化信号功率和噪声功率的比例,最大化可达保密速率.仿真结果验证了本文提出的人工干扰策略的有效性. 相似文献
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无线认知网络(Wireless Cognitive Network,WCN)是在认知无线电(Cognitive Radio,CR)技术基础上形成的网络形态,是当今通信技术的前沿研究领域之一。无线认知网络具有高度智能化能力,能感知网络的环境信息和分辨当前的网络状态,并根据这些状态进行相应的规划、决策和响应。WCN主要应用于机会频谱接入(Opportunistic Spectrum Access)主用户(合法的授权用户,具有较高的优先权接入频谱),而次用户(具有认知功能的非授权用户)通过智能感知周围的无线环境,并在对主用户不造成有害干扰的情况下机会接入授权频谱。 相似文献
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认知中继网络中,对信道进行分配可以有效地提高端到端吞吐量。对三节点认知中继网络下的信道分配进行了研究。中继节点采用解码转发协议时,提出了一种次优的分配方法,将信道按信道增益排序,然后逐个地分配中继信道。中继节点采用放大转发协议时,给出了最优的信道分配方法,提出了一种次优的信道分配方法。次优方法逐个地比较中继信道采用传统协作方式传输时的端到端吞吐量、分配为双跳信道S-R和R-D链路时的端到端吞吐量完成分配。和最优方法相比,两种次优方法以较小的性能损失换取了计算复杂度的降低。给出了数值仿真,比较了两种传输方式下的端到端吞吐量性能,验证了以上方法的有效性。通过对比仿真时间,比较了最优方法和次优方法的计算复杂度。给定信道总数,对次优方法下信道分配后的比例进行了仿真,发现待分配中继信道以1/3的比例分配为直传信道;而在放大转发下,待分配中继信道几乎不被分配为双跳信道。 相似文献
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《电子技术与软件工程》2017,(24)
随着网络技术的发展,无线设备的大量增加,为频谱资源的使用带来了极大的压力。频谱资源利用率低让网络发展进入了一个停滞期。但随着认知无线电技术的提出,与其在信道交汇中的应用,改变了网络频谱资源使用不均衡的现状,推动了网络技术的发展。本文对认知无线电技术与信道交汇的基本内涵分别进行了阐述,说明认知无线电技术与信道交汇之间的关系,进而提出了认知无线电技术的信道交汇策略,从调整信道算法、整合频谱资源、重构信道交汇方向等方面展开论述,旨在促进信道交汇,促进网络技术的发展。 相似文献
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One of the major drawback of an orthogonal frequency division multiplexing based cognitive radio is high out‐of‐band leakage that can severely affect primary users operating in adjacent bands. The paper aims to design a new spectral precoding scheme that minimizes Adjacent Channel Leakage Ratio (ACLR) while retaining the orthogonality among data symbols. The problem is formulated as trace ratio minimization subjected to unitary constraint that can be effectively solved using iterative methods. The proposed precoder's error performance is similar to uncoded orthogonal frequency division multiplexing system due to orthogonal multiplexing. Also, it is practically realizable due to lower complexity. The scheme also extends for distinct ACLR requirements in upper and lower adjacent bands. A relative important factor is introduced so as to flexibly control the interference leakage in upper and lower adjacent channels. An algorithm is suggested for choosing suitable values of this factor. Simulation results display the superiority of proposed scheme over existing techniques in terms of ACLR and throughput. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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感知无线电技术允许多个感知用户之间公平协调共享频谱,由于基站在同一频率同一时隙下可以和几个移动终端同时通信,这将引起用户间的共信道干扰(CCI)。本文引入了预编码的思想,多个感知用户感知并共享频谱时在发射端加入预编码矩阵,基于信漏噪比(SLNR)的预编码同时消除了共信道干扰(CCI)和噪声,提高了感知系统性能。仿真结果说明采用了基于SLNR的预编码后系统性能得到了明显改善,且发射天线数越多,系统性能越好。 相似文献
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认知无线电是通信领域在软件无线电概念之后出现的又一新概念,其主要关注于系统通过感知操作环境的变化调整系统工作参数。叙述了认知无线电的概念及与软件无线电的关系,对其构架和关键技术进行了介绍,并分析了认知无线电在军事通信领域的优势及面临的挑战,对于我军通信系统的升级建设具有积极作用。 相似文献
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ZHAO Cheng-lin ZHANG Kun SUN Xue-bin JIANG Ting Key Laboratory of Universal Wireless Communication Ministry of Education Beijing University of Posts Telecommunications Beijing China 《中国邮电高校学报(英文版)》2011,(4):59-64
Orthogonal frequency division multiplexing(OFDM)is considered to be one of the promising schemes for cognitive radios(CR)systems,due to its flexibility in spectrum shaping.However,the traditional way of spectrum-notching failed to suppress out-of-band leakage enough,resulting in interference with licensed users(LUs).A novel spectrum shaping scheme is proposed in this article,where a precoder with interference suppression sequence(ISS)is for the first time introduced for shaping the spectrum of OFDM signals in OFDM-based CR systems.The precoder matrix together with ISS matrix is obtained by minimizing the power of out-of-band interference,which results in the sufficient interference suppression of OFDM signal to LUs.Analysis and simulation results show that the proposed scheme can significantly suppress the interference power to LUs at a little cost of precoding efficiency.Meanwhile,the peak-to-average-power-ratio(PAPR)is invariable and the bit-error-rate(BER)performance over Rayleigh fading channel is improved. 相似文献
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Zhijin Zhao Shiyu Xu Shilian Zheng Junna Shang 《Wireless Communications and Mobile Computing》2009,9(7):875-881
One of the basic capabilities of cognitive radio is to adapt the radio parameters according to the changing environment and user needs. This paper proposes a new adaptation method which uses particle swarm optimization (PSO) to optimize cognitive radio parameters given a set of objectives. The procedure of the proposed method is presented and multicarrier system is used for simulation analysis. Experimental results show that the proposed method performs far better than genetic algorithm (GA)‐based adaptation method in terms of convergence speed, converged fitness values, and stability. The proposed method can also provide the tradeoffs of the objective functions, and the resulting parameter configuration is consistent with the weights of the objective functions. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Rongfei Fan Jianping An Hai Jiang Xiangyuan Bu 《Wireless Communications and Mobile Computing》2016,16(16):2636-2648
This paper investigates the channel selection and slot time configuration in a cognitive radio network with a number of potential channels. Each channel alternates between ON state (i.e., the primary user is using the channel) and OFF state (i.e., the primary user does not use the channel), and the state evolution process is modeled as a continuous‐time Markov process. The traffic parameters (the transition rates) of the Markov process also evolve with time, modeled as a discrete‐time Markov process. A secondary user adopts a slotted structure with dynamic slot length. At each slot, the secondary user needs to determine which channel to sense and, if the channel is sensed idle, how long the slot length should be. Considering both the amount of data that the secondary user can transmit and the duration when the secondary user interferes with primary activities, a reward definition is given. Based on the reward definition, an adaptive channel selection and slot length configuration method is proposed, which includes a reward maximization procedure to maximize the achieved reward and an update procedure for the channel state belief vector and traffic parameter state belief vector. Numerical results are given to demonstrate the effectiveness and features of the proposed method. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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在认知无线网络中,针对系统中所有用户能否接入同一信道进行通信的问题,提出了适用于不同情形的联合优化方案.在系统不可行的情形下,提出了联合优化功率和接入控制的方案.由于接入控制是NP问题,于是利用所提LP-PSO算法来实现优化控制,并分析和证明了所提算法的收敛性.在系统可行的情形下,提出了联合优化功率和传输速率分配的方案,通过改进拉格朗日对偶(Lagrange duality)算法来实现优化控制.数值结果分析表明,相比其他接入控制算法,虽然所提算法的时间复杂度有所增加但能够快速收敛,在有效地提高接入量的同时还能降低功率消耗,并能使传输速率得到更公平的分配. 相似文献