Matched Filter Based Spectrum Sensing When Primary User Has Multiple Power Levels

In this paper,we investigate the matched filter based spectrum sensing in a more reasonable cognitive radio(CR) scenario when the primary user(PU) has more than one transmit power levels,as regulated in most standards,i.e.,IEEE 802.11 Series,GSM,LTE,LTE-A,etc.This new multiple primary transmit power(MPTP) scenario is specialized by two different targets:detecting the presence of PU and identifying the power level.Compared to the traditional binary sensing where only the presence of PU is checked,SU may attain more information about the primary network(making CR more "intelligent") and design the subsequent optimization strategy.The key technology is the multiple hypothesis testing as opposed to the traditional binary hypothesis testing.We discuss two situations under whether the channel phase is known or not,and we derive the closed form solutions for decision regions and several performance metrics,from which some interesting phenomenons are observed and the related discussions are presented.Numerical examples are provided to corroborate the proposed studies.

Dynamic Matching-Based Spectrum Detection in Cognitive Radio Networks

Cognitive Radio Network provides an opportunity to reduce the spectrum resource crisis by allowing secondary users to access the idle spectrum allocated to primary users. The precondition of spectrum sharing is to obtain the Spectrum Availability Information(SAI). Energy detection is a typical technology to get SAI. With the mobility of primary users, the energy received by secondary users varies greatly with the distance from the target primary users. Most of the existing energy detection algorithms that use fixed thresholds are not suitable. We propose a Dynamic Matching-Based Spectrum Detection(DMBSD) scheme which can detect sensing data, reduce the impact of malicious data and make final sensing results more accurate with dynamic threshold setting and data matching. Simulation results show that the proposed scheme can detect tempered data, and increase detection probability by decreasing false alarm probability and missed detection probability.

Angular spectrum characters of high gain non-critical phase match optical parametric oscillators

The angular spectrum gain characters and the power magnification characters of high gain non-walk-off colinear optical parametric oscillators have been studied using the non-colinear phase match method for the first time.The experimental results of the KTiOAsO 4 and the KTiOPO 4 crystals are discussed in detail.At the high energy single resonant condition,low reflective ratio of the output mirror for the signal and long non-linear crystal are beneficial for small divergence angles.This method can also be used for other high gain non-walk-off phase match optical parametric processes.

一种基于Spectrum原子的雷达辐射源信号识别方法

为了提高雷达辐射源信号的正确识别率以满足现代电子对抗的需求,该文提出了一种新的雷达辐射源信号识别方法。在过完备多尺度Spectrum原子库基础上,采用匹配追踪(MP)方法对信号进行原子分解,并通过FFT降低MP搜索过程的时间复杂性,在此基础上,对本征Spectrum原子参数进行有效降维,提取具有分类意义的原子特征向量,同步实现信号的自动分类和参数估计。实验结果表明,该方法在低信噪比环境下不仅可以获得高的信号类别正确识别率,同时具有准确的参数估计结果,证实了所提出方法的有效性。

Artificial ground motion compatible with specified ground shaking peaks and target response spectrum

This article describes a hybrid simulation method to generate artificial ground motion time histories that are compatible with specified peak seismic acceleration, velocity and displacement as well as the target response spectrum of absolute acceleration. First, based on traditional methods that match the target spectrum in the frequency domain, an initial acceleration time history was synthesized to satisfy the specified peak acceleration, target spectral acceleration and intensity envelope. Second, by using the inversion formula of the seismic input to a linear single-degree-of-freedom system and by superimposing a series of narrow-band time histories in the time domain, the initial time history is further modified to allow its peak velocity and displacement to approach the targets and improve its matching precision with the target spectrum. Numerical examples are provided to demonstrate that the proposed method achieves good agreement with the target values.

改进型Code-Matched交织器

Turbo码作为信道编码方案 ,可以获得较高的误比特率 (BER)性能 ,而交织器的设计是影响Turbo码性能的关键环节 .笔者在码的重量分析的基础上提出了一种改进型Code Matched交织器 ,它可以减少低重量码的数量 ,从而提高Turbo码的性能 .这种改进型Code Matched交织器可以适用于多种不同生成矩阵产生的Turbo码 ,而且不会影响Turbo码在中、高信噪比处的性能 ,同时 ,在Rayleigh信道下 。

Research and Implementation of Text Similarity System Based on Power Spectrum Analysis

The paper proposed the research and implement of text similarity system based on power spectrum analysis. It is not difficult to imagine that the signals of brain are closely linked with writing process. So we build text modeling and set pulse signal function to get the power spectrum of the text. The specific detail is getting power spectrum from economic field to build spectral library, and then using the method of power spectrum matching algorithm to judge whether the test text belonged to the economic field. The method made text similarity system finish the function of text intelligent classification efficiently and accurately.

A WGN和衰落信道下具有改进型Code-matched交织器的Turbo码(英文)

提出了一种改进型的Code Matched交织器,它能减少低重量码的数量,从而提高Turbo码的性能。这种改进型的Code Matched交织器可以适用于多种不同生成矩阵产生的Turbo码,而且不会影响Turbo码在中高信噪比处的性能。同时,在Rayleigh信道下,这种交织器能降低错误平台。

Novel matched filtering method and its application in radar system

The method of using a narrowband filter to realize matched filtering is derived.A novel method of using spectrum sampling to realize matched filtering is presented,and the method can conquer the disadvantages that the narrowband filter cannot adopt the adaptive scheduling of phased array radars and realize matched filtering for several waveforms.A novel error extraction method is proposed,which uses a time division multipath method to realize the intermediate frequency extraction.This method can save lots of space for vehicle-born radar systems,reduce the influence of amplitude and phase distortion caused by devices,and enhance the system reliability.Simulation results show that the spectrum sampling method is applicable,and the implementation of frequency spectrum sampling is elaborated.

COOPERATIVE WIDEBAND SPECTRUM SENSING BASED ON SEQUENTIAL COMPRESSED SENSING

Compressed sensing offers a new wideband spectrum sensing scheme in Cognitive Radio (CR). A major challenge of this scheme is how to determinate the required measurements while the signal sparsity is not known a priori. This paper presents a cooperative sensing scheme based on se-quential compressed sensing where sequential measurements are collected from the analog-to-information converters. A novel cooperative compressed sensing recovery algorithm named Simul-taneous Sparsity Adaptive Matching Pursuit (SSAMP) is utilized for sequential compressed sensing in order to estimate the reconstruction errors and determinate the minimal number of required meas-urements. Once the fusion center obtains enough measurements, the reconstruction spectrum sparse vectors are then used to make a decision on spectrum occupancy. Simulations corroborate the effec-tiveness of the estimation and sensing performance of our cooperative scheme. Meanwhile, the per-formance of SSAMP and Simultaneous Orthogonal Matching Pursuit (SOMP) is evaluated by Mean-Square estimation Errors (MSE) and sensing time.

Despreader for Direct Sequence Spread Spectrum System and Its Performance Analysis

A new type of despreader for direct sequence spread spectrum signal is proposed. Compared with traditional despreaders, the new despreader does not contain hard decision ware or handle binary sequence any more, and the locally stored spread spectrum signals are pre-modulated baseband signals (such as Gaussian minimum shift keying (GMSK) signals), which are much more similar to the received spread spectrum signals. Moreover, the missed detection probability of the despreader is about one order of magnitude lower than that of traditional ones. Based on the maximum likelihood criterion and phase probability density function of demodulated signal, a new method of ana- lyzing the despreaders’ performance is put forward, which is proved to be more accurate than traditional methods according to the numerical results. Finally, an adaptive despreader under different signal-to-noise ratios is given.

Design of New SAWDQPSK Matched Filter

A new surface acoustic wave differential quadraphase shift key(SAW DQPSK) spread spectrum(SS) signal matched filter based on the fusion of SS and differential modulation is reported. The design of multi-phase coded SAW matched filter is proposed rather than another design of SAW DQPSK filter, which can cut in a half of the delay time of SAW DQPSK matched filter and SAW fiyed delay line(FDL) used for differential demodulation. This breakthrough is made the system largely reduce a size and process much easily. This method can also be feasible in other SAW MPSK matched filter design especially when the modulation phase number is larger than 4. The design example and its experimental results are given.

A Spectrum Sensing Framework for UWB-Cognitive Network

Due to that the Ultra Wide Band (UWB) technology has some attractive features like robustness to multipath fading, high data rate, low cost and low power consumption, it is widely use to implement cognitive radio network. Intuitively, one of the most important tasks required for cognitive network is the spectrum sensing. A framework for implementing spectrum sensing for UWB-Cognitive Network will be presented in this paper. Since the information about primary licensed users are known to the cognitive radios then the best spectrum sensing scheme for UWB-cognitive network is the matched filter detection scheme. Simulation results verified and demonstrated the using of matched filter spectrum sensing in cognitive radio network with UWB and proved that the bit error rate for this detection scheme can be considered acceptable.

基于图着色和三维匹配的车联网资源分配算法

车联网通信通过多个车辆对车辆(vehicle to vehicle,V2V)链路复用同一车辆对基础设施(vehicle to infrastructure,V2I)链路的资源来缓解频谱短缺问题,但频谱复用会导致V2I通信服务质量下降,因此降低系统干扰、提高系统容量成为研究热点。提出一种基于图着色和三维匹配的车联网资源分配算法,首先用图着色法对V2V链路分簇,然后求解V2I链路和V2V链路的发射功率,最后通过三维匹配算法对V2I链路、V2V簇和资源块进行信道资源的优化分配,从而降低使用同一资源的链路之间的干扰。理论分析及仿真结果表明,所提方法提高了V2I链路总和速率,并在相对较少的迭代次数下收敛到次优解。

Research on Radiant Carrier of Matching Radiant Type Far Infrared Textiles

This paper deals with the radiation effects of different kinds ofradiant carriers used in making far infrared textile materials.From two radiation experiments,methods of testing radiation ef-fects of carriers have been found,results of the experiments arediscussed.Finally,some conclusions for choosing appropriateradiant carrier are drawn.

基于小波变换的长周期桥梁选波方法研究

时程分析输入地震波的选取对长周期大跨度桥梁影响显著。本文基于规范目标谱,以MATLAB为依托,通过选取最优小波基并利用小波系数迭代法实现频域调整,使地震波反应谱不断逼近给定目标谱,最后结合相对误差和长周期拟合参数两个指标进行综合评价,选取适用于长周期大跨度桥梁的时程分析地震波,提出长周期桥梁全过程批量选波方法。将该方法应用于奉节长江大桥,与基于时域调整方法的Seismo Match选波软件对比选波效果,并将选波结果应用于背景桥梁的时程分析。结果表明,利用本文选波方法所得结构关键截面响应与软件选波所得响应在横桥向和竖桥向存在一定差异。本文方法可为长周期大跨度桥梁时程分析选波提供参考。

AN ADAPTIVE MEASUREMENT SCHEME BASED ON COMPRESSED SENSING FOR WIDEBAND SPECTRUM DETECTION IN COGNITIVE WSN

An Adaptive Measurement Scheme (AMS) is investigated with Compressed Sensing (CS) theory in Cognitive Wireless Sensor Network (C-WSN). Local sensing information is collected via energy detection with Analog-to-Information Converter (AIC) at massive cognitive sensors, and sparse representation is considered with the exploration of spatial temporal correlation structure of detected signals. Adaptive measurement matrix is designed in AMS, which is based on maximum energy subset selection. Energy subset is calculated with sparse transformation of sensing information, and maximum energy subset is selected as the row vector of adaptive measurement matrix. In addition, the measurement matrix is constructed by orthogonalization of those selected row vectors, which also satisfies the Restricted Isometry Property (RIP) in CS theory. Orthogonal Matching Pursuit (OMP) reconstruction algorithm is implemented at sink node to recover original information. Simulation results are performed with the comparison of Random Measurement Scheme (RMS). It is revealed that, signal reconstruction effect based on AMS is superior to conventional RMS Gaussian measurement. Moreover, AMS has better detection performance than RMS at lower compression rate region, and it is suitable for large-scale C-WSN wideband spectrum sensing.

基于混隐色特征背景引导融合的伪装效能评估

现有迷彩伪装效能评估方法重点关注目标与背景在颜色、纹理等特征上的相似度,未能从伪装策略角度分析目标边缘和表面的融合程度,无法准确评估复杂环境下目标的伪装效果。本文提出一种基于混隐色特征背景引导融合的伪装效能评估模型,利用多重分形理论和Gabor滤波器估计目标轮廓和表面破坏程度;引入特征拥塞指数计算背景复杂度,通过逻辑斯蒂方程自适应调整评估特征权重,提高模型对环境变化的适应性。实验表明,该模型在Search_2数据集上的搜索时间相关性系数(皮尔逊相关系数、斯皮尔曼相关系数、均方根误差)分别达到0.888、0.773、0.054,在自建CamData数据集上分别达到0.835、0.805、0.126,评估结果与人眼搜索实验结果符合性较高,能够有效表征目标在不同复杂场景下的伪装效能。

球-柱-球复合壳体结构声辐射建模及特性分析

针对典型复合材料轴对称结构的外部声辐射问题,本文建立了基于结构完整边界的广义谱-配点边界元法的结构声辐射分析模型。从一阶剪切层合壳理论出发,推导了复合材料结构振动能量方程,引入广义谱方法和边界元方法的思想,将Helmholtz积分方程转化为边界积分方程,再将位移、声学变量和Green函数等展开为周向Fourier多项式和轴向Chebyshev多项式的形式,经化简得到一维半解析声振耦合求解的声场方程。对于浸没在轻质和重质流体中的壳体结构,均采用强耦合的处理方式对结构声问题进行求解。通过数值结果验证了本文方法的正确性,分析了各向同性均匀材料和正交各向异性球-柱-球复合壳体的声辐射问题,并讨论了不同载荷方式、铺层角度等因素对复合壳体结构声辐射的影响。结果表明:对于铺层为[90°/±θ/0°]S的玻璃纤维材料复合壳体结构,随着铺层角的增大,组合结构的轴向拉伸和弯曲刚度逐渐减小,周向的刚度得到加强,并在结构弯曲-扭转耦合效应的作用下,壳体结构的辐射声功率级响应曲线的峰值频率向高频发生偏移。