共查询到20条相似文献,搜索用时 62 毫秒
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针对升空通信平台大规模多输入多输出(Multiple-Input Multiple-Output,MIMO)系统中在通信接入阶段遭受导频攻击引入的信息泄露问题,提出了一种基于空间波束不变性的导频接入攻击检测与消除方法。该方案基于用户空间波束域信道结构特征,在缺少信道先验信息的条件下使用点排序簇结构(Ordering Points to Identify the Clustering Structure,OPTICS)聚类算法,分离提取接入攻击与合法用户的波束域信道,消除接入攻击导致的信号损伤,实现合法用户信号安全传输。仿真结果表明,所提方案能够有效降低导频接入攻击对系统安全传输的影响。 相似文献
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针对传统信息论物理层安全研究中,对合法用户信道质量要求较高的问题,文中提出随机波束成型的物理层安全传输方法。该方法通过在主信道特征向量的垂直方向构造人工随机波束成型信道,使得合法用户与窃听方信道传输特征的差异性转化为信道质量的差异,最终得到正的保密容量。为保证算法的完备性,文章解决了三方面问题:1)给出随机波束成型的空间构造方法;2)随机波束成型方法的保密容量和最佳信源分布;3)人工随机信道的构造方法。最后针对采用随机波束成型算法的发送分集系统,通过设计、仿真其噪声发生和功率分配方案,进一步说明即使在合法用户信道质量差的情况下,随机波束成型传输算法也可获得保密传输容量。 相似文献
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在正交频分复用(OFDM)系统中使用空频传输分集是未来宽带无线通信中的重要技术。由于在各个终端采用多天线进行收发,导致使用空频-OFDM(SF-OFDM)传输分集的系统受到增强的共信道干扰(CCI)。本文提出了一种适用于SF-OFDM系统的波束形成方案,该方案能有效的抑制共信道干扰。在该方案中,基于盲转向的波束形成被应用于SF-OFDM系统中。分析和仿真结果表明,该方案具有良好的共信道干扰抑制能力。此外,该方案能够利用不同波达角(DOA)信号间的相对时延来增强系统性能。 相似文献
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水下可见光通信(UVLC)是实现高速宽带信息传输的有效方案,但由于受到信道中吸收、散射和湍流的不利影响而面临着许多困难。针对水下湍流信道中多径和衰落带来的影响,提出了一种光正交频分复用(O-OFDM)等增益合并的分集方案,根据广义的朗伯定律得到信道增益,通过对数正态分布模拟信号衰落。采用蒙特卡洛方法对正交幅度调制(QAM)的非对称削波光正交频分复用(ACOOFDM)和直流偏置光正交频分复用(DCO-OFDM)两种分集系统进行建模仿真,分析高斯信道和弱湍流信道下系统的误比特率,探讨不同分集数目和闪烁系数情况下的分集增益。研究结果验证了分集是降低湍流影响的有效手段,有利于改善水下信息传输性能,为弱湍流信道下正交频分复用可见光通信系统的设计、预测和评估提供参考。 相似文献
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根据OFDM信号的特点,在深入分析使用训练序列和导频符号进行波束形成这2类算法的基础上,提出一种适用于无线局域网分组传输情况下的波束形成方法,此方法结合了上述2类算法的优点,同时使用训练序列和导频符号在时域进行波束形成。在瑞利衰落信道下的计算机仿真结果表明,该算法有较好的性能。 相似文献
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Michael Reilly 《半导体技术》2004,29(12)
DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system. 相似文献
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Thomas M.Trexler 《半导体技术》2004,29(5)
From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test. 相似文献
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The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation. 相似文献
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The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high. 相似文献
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Today, micro-system technology and the development of new MEMS (Micro-Electro-Mechanical Systems) are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible. 相似文献
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Qi-jiang Ran Pei-de Han Yu-jun Quan Li-peng Gao Fan-ping Zeng Chun-hua Zhao 《光电子快报》2008,4(4):239-242
This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel's. 相似文献
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Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers
A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it. 相似文献
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A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working. 相似文献
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《中国通信》2014,(7)
正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks 相似文献
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《中国通信》2014,(8)
正Information Centric Networking Information-Centric Networking(ICN) is an emerging direction in Future Internet architecture research,gaining significant tractions among academia and industry.Aiming to replace the conventional host-to-host communication model by a data-centric model,ICN treats data content as the first 相似文献