基于区域融合的分布式CPAR信号检测

本文提出了多传感器检测区域的划分,以及先分区融合再系统融合的方法,并且在不同的检测区域,传感器采用不同的门限。给出了该方法的虚警概率和检测概率表达式,并介绍了它在分布式CFAR检测系统中的应用。结果表明,通过设置不同的门限,可以提高系统的检测概率。     

认知无线网络中动态双门限协作频谱感知性能的优化方案

频谱感知作为认知无线电的关键技术,得到广泛深入的研究。其中衡量协作频谱感知性能的主要参数为全局虚警概率和全局漏检概率,它们之和被定义为全局错误概率。本文研究基于双门限能量检测的协作频谱感知性能的优化方案,首先,固定双门限能量检测的检测门限值,对表决融合准则的投票门限进行优化,使得在该能量检测门限值条件下,协作频谱感知的全局错误概率最小;然后在表决融合准则的投票门限取最优值的前提下,对双门限能量检测的检测门限值进行了优化,在不同接收信噪比条件下,最优的检测门限值是动态的,所以要根据信噪比确定最优的检测门限值,使得协作频谱感知的全局错误概率在各信噪比条件下都达到最小值,从而提高了协作频谱感知的性能。仿真结果表明,表决融合准则的投票门限和双门限能量检测的检测门限值取得各自的最优值时,全局错误概率最低,检测性能最好。      

CFRP层板缺陷红外热波雷达成像检测概率研究

建立了Chirp调制激光激励的红外热波雷达成像检测系统,提出了基于分数阶傅里叶变换的Chirp锁相算法和基于希尔伯特变换时域积分的HT算法,实现了对CFRP层板缺陷的检测;合理设计了模拟缺陷的尺寸分布范围与缺陷判定准则,采用Hit/miss法分析了信号提取算法对检测概率的影响;给出了不同检测参数与判定阈值情况下,相关算法、Chirp锁相算法和HT算法提取结果的检测概率数据,确定了红外热波雷达成像系统对CFRP层板缺陷的检测概率水平。     

一种多基地雷达检测概率的全局优化方法

提出一种多基地雷达检测概率的全局优化方法.首先讨论在多个接收站具有不同接收信噪比的条件下,对接收站判决进行融合后,目标总的检测概率和虚警概率的变化;然后以目标总的检测概率为目标函数,对各个接收站的恒虚警率检测门限进行调整,实现了多基地雷达检测概率的优化.     

瑞利衰落环境中二维扩频矩阵的序贯捕获性能分析

该文给出了一种二维扩频矩阵的时间同步方法,分析了此方法的捕获概率和虚警概率;在不同归一化门限条件下,给出了数值结果。分析结果表明,经映射的二维扩频系统等效为一维扩频系统,采用一维扩频的同步方法能使二维扩频系统获得良好同步性能,且方法简单。     

Adaptive mean queue size and its rate of change: queue management with random dropping

The random early detection active queue management (AQM) scheme uses the average queue size to calculate the dropping probability in terms of minimum and maximum thresholds. The effect of heavy load enhances the frequency of crossing the maximum threshold value resulting in frequent dropping of the packets. An adaptive queue management with random dropping algorithm is proposed which incorporates information not just about the average queue size but also the rate of change of the same. Introducing an adaptively changing threshold level that falls in between lower and upper thresholds, our algorithm demonstrates that these additional features significantly improve the system performance in terms of throughput, average queue size, utilization and queuing delay in relation to the existing AQM algorithms.     

基于动态自适应双门限能量检测的序贯协作频谱感知算法

针对在一般高斯白噪声环境中,传统的双门限能量检测频谱感知算法忽略确定两门限之间的感知信息的问题,该文提出一种基于动态自适应双门限能量检测的序贯协作频谱感知算法。新算法以最优化检测概率为目标,采用序贯方式对协作用户进行动态自适应双门限建模,并对处于两门限之间的接收能量值进行软判决。进一步地,新算法能自适应动态调整门限大小和各判决区域协作用户数,以达到最大化检测概率和最优化受试工作特征曲线的目的。理论分析和仿真结果表明,与经典的双门限能量检测算法相比,提出算法具有更优的检测概率。     

基于概率计算的虚假点消除算法研究

针对无源测向交叉定位在多目标辐射源的情况下存在的虚假点问题,提出了一种基于概率计算的虚假点消除改进算法。该方法根据测向信息,构造误差概率密度和矩阵,根据矩阵参数将测量区域内概率密度和的最大值点判定为辐射源位置。然后通过设定阈值,依次找出其余辐射源位置,提高了在测向误差较大时的性能,达到消除虚假点的目的。仿真证明了该算法的有效性。     

基于Wigner-Hough变换的LFM信号检测性能分析

根据Wigner-Hough变换思想和广义似然比检验理论,分析了双门限情况下线性调频信号的检测性能,给出了虚警概率和检测概率的数学表达式,该表达式是Hough变换的积累单元数和检测门限的函数,然后对概率密度函数进行了合理近似,并给出了Hough变换的积累单元数计算公式,最后的计算机仿真比较了傅立叶变换和Wigner-Hough变换的LFM(Linear Frequency Modulated)信号检测性能和基于Wigner-Hough变换的不同目标起伏类型的LFM信号检测性能.     

Femtocell网络中基于双门限的两层协作频谱感知技术

在Femtocell和Macrocell构成的两层异构网络中,前人提出运用认知无线电的技术来解决网络中存在的干扰问题,但大多数研究主要集中在频谱资源的管理上,没有提出高效的频谱检测方法。本文结合认知无线电中频谱感知技术提出了基于双门限的两层协作频谱感知,检测出空洞的频谱资源分配给Femtocell用户使用,既能提高频谱资源的利用率,又能有效的抑制Femtocell与Macrocell之间的干扰。文中推导出了Femtocell用户基于双门限的两层频谱感知的检测概率和虚警概率,给出了Femtocell网络中感知信息两比特编码的融合准则和基于双门限的两层协作频谱感知的具体实施方法。仿真结果表明,所提算法能够有效提高Femtocell用户的频谱检测概率,通过对感知信息进行两比特编码,再将编码后的信息发送至融合中心进行融合,能够有效的提高整个系统的检测性能,抗噪声能力强。      

Optimization of a parallel distributed detection system using distance measures

In this paper, we use both J-divergence and Bhattacharyya coefficient as distance measures to optimize a parallel distributed detection system consisting of N local detectors and a global decision maker. The optimization is obtained by allowing the thresholds of the local detectors to be functions of the global probability of false alarm. Numerical results for the case of four and six local detectors are obtained. These results indicate the superiority of our approach over those reported in the literature in which the local thresholds were specified without taking the level of global probability of false alarm into account.     

机载红外搜索跟踪系统有效探测区域研究

针对机载红外搜索跟踪(IRST)系统在实际空战中发现概率过低的问题,论文尝试将作用距离与发现概率相结合,提出了有效探测区域的概念,并分别建立了水平、俯仰两种探测方式下有效探测区域模型;接着讨论了在复杂作战环境下,所建立的模型随发现概率、作用距离、大气透过率、目标飞行速度的变化情况。仿真结果表明,探测区域范围是随着上四种因素的变化而实时变化的,并且在两机相距百公里以上,气象恶劣、目标低速飞行时,有效探测区域仅仅是目标尾后上方很小的一块区域。机载IRST系统可以依据论文给出的变化关系,在探测过程中,动态建立信号视场中检测阈值与复杂因素的函数关系,以提高发现概率。论文为充分发挥机载IRST系统的作战使用性能提供了理论参考。     

认知无线电中基于感知信息量化的合作频谱感知

针对认知无线电频谱感知性能的提高与传输开销的矛盾,本文提出了一种基于感知信息量化的合作频谱感知方案。该方法对各认知用户的本地检测结果采用3个判决门限进行2比特位的量化,在融合中心处对量化信息加权处理后,得到最终主用户是否存在的判决。本文详细研究了采用该方案的检测概率,虚警概率和吞吐量,理论分析和仿真结果表明,该方法在每个认知用户只增加1bit传输开销的前提下能够极大的改善检测性能,实现了检测性能与传输开销的较好权衡。     

Two effective methods to detect anomalies in embedded systems

Current-day embedded systems are very vulnerable to faults and defects. Anomaly detection is often the primary means of providing early indication of faults and defects. This paper presents two methods for detecting anomalies in embedded systems. The first method, buffer based detector, constructs a buffer consisting of events from a stream of data considered to be normal. Consequently, during test stage, if an event does not exist in the buffer, a miss will happen. An anomaly exists in test data provided that the hit rate of the buffer does not reach a predefined threshold. The second method namely probabilistic detector employs the probability of data events to evaluate the behavior of system. In order to measure the probability of events in the system, sampling of two events with distinct distance is done. Eventually, during test stage, the probability of events can be measured. An anomaly exists in test data provided that this probability does not reach a predefined threshold. A comparison between these two methods and other typical methods has been done based on detection coverage, area overhead and delay overhead. The experiments on 112 standard benchmarks show that the proposed methods can detect 100% of anomalies. Also, the area overhead of the proposed detectors grows linearly, while the area overhead of other typical detectors grows exponentially by the increase in one of the detector's parameters.     

Optimal multi-threshold quantization scheme for bioinformatics inspired cooperative spectrum sensing in cognitive radio networks

Hard decision combination provides bandwidth efficiency but the results produced are unreliable while soft decision combination has better results but at the expense of much consumption of bandwidth. An acceptable trade-off is achieved between the two in case of quantized decision combination. In this paper an optimal quantization scheme is proposed in which the local sensing information is quantized so the maximum detection probability is met while the false alarm probability remains under a certain constraint. The proposed optimal scheme works on the basis of energy detection and the local quantization thresholds are found through iterative search. Smith–Waterman algorithm (SWA) is used to compare the local sensing reports of the CR users and similarity indexes are found for the CR users. The local sensing decisions of the CR users below a certain calculated threshold are rejected and are not included in the final decision combination at the FC. For detailed analysis, SWA-based rules of decision combination with optimal quantization thresholds are compared with a scheme that employs SWA-based rules of decision combination with heuristically selected quantization thresholds and a conventional majority combination scheme. Simulation results show that the proposed scheme performs better than the other two schemes.     

不完全量测下基于后验置信度残差检测的光电跟踪滤波器设计

 不完全量测下残差检测算法的设计是光电跟踪滤波器设计的关键,算法的正确检测概率直接影响到跟踪滤波器的估计性能.为了进一步提升传统残差检测算法的正确检测概率,提出了一种基于后验置信度的残差检测算法.其主要思想是在传统残差检测算法的基础上首先增加一个检测门限,对处于两个门限之间的残差,利用模糊隶属度函数方法进行模糊化,得到残差的似然概率,进而结合跟踪系统的先验探测信息,计算出探测数据的后验置信度,并根据计算结果对跟踪系统的数据探测情况进行判定.进一步,基于后验置信度残差检测算法,在不完全量测下设计了基于无偏转换量测的光电跟踪滤波器,并给出了跟踪系统统计意义下的Cramer-Rao下界(CRLB).Monte-Carlo仿真表明:基于后验置信度残差检测的光电跟踪滤波器,与基于传统残差检测的光电跟踪滤波器相比,估计性能有了进一步提升,特别是当跟踪系统探测概率较低时,估计性能提升更加显著,并且估计误差均方差(RMSE)已逼近跟踪系统统计意义下的CRLB.     

二维扩频系统同步技术研究

二维扩频通信系统是近年来提出的新的扩频通信方式,由于二维扩频系统从时域和频域上分别对数据信号进行频谱扩展,因此他同时具有时域扩频和频率扩频通信系统的特点。对于一个实际系统而言,同步是信号正确解调和恢复的前提。针对二维扩频特殊的时频域扩频矩阵结构,提出广义二维扩频矩阵的时间同步算法:该算法将二维扩频矩阵等效为一个一维时间序列,采用序贯捕获的方法捕获此时间序列的第一径,从而完成二维扩频矩阵的时间捕获。该算法不需要在数据序列中插入循环前缀,因而减少了系统开销,提高了带宽利用率。同时,对其在瑞利衰落环境中的同步性能进行详细的理论分析和推导。分析结果表明:该同步方法简单,具有良好的同步性能。     

一种改进的基于单高斯模型的红外异常目标检测算法

基于单高斯模型的红外异常目标检测算法是一种常见的能自适应更新背景模型的检测算法。该算法对各个像素的输出响应进行高斯建模,通过设定的阈值确定目标像素点是否为前景像素点,从而达到检测的目的。本文在单高斯模型的基础上,提出一种改进的异常检测算法,该算法利用奈曼-皮尔逊准则选取最佳阈值,克服了根据经验值选取阈值的局限性,为最佳判决阈值的选取奠定了理论基础,使得在虚假率一定的情况下,检测概率达到最高。实验证明,将常见的经验阈值与本文确定阈值进行比较,本文算法确定的阈值检测效果更佳。     

Application of DAPSK in HF communications

The 64-DAPSK-OFDM transmission techniques for HF communications are investigated in this paper. The error probability of 64-DAPSK in mobile fading channels is evaluated, the optimum ring ratio is given and detection thresholds are determined. Extensive computer simulation results show that 64-DAPSK-OFDM is superior to the widely adopted 64-QAM and it can be a potential choice for spectrally efficient digital transmission over different HF channels.     

AAL2分组话音复接器缓冲器队列门限值的确定方法

该文研究了带比特丢弃的AAL2分组话音复接器缓冲器队列门限值的确定方法,提出用话音分组作为缓冲器队列门限值的单位,给出了确定门限值的计算公式,并对输出链路容量为384kb/s的情况进行了计算机仿真。仿真结果表明,作者提出的门限值的确定方法可获得较小的平均分组时延和较低的平均分组丢失率,计算简便,易于实现,是一种很好的确定缓冲器队列门限值的方法。