共查询到20条相似文献，搜索用时 406 毫秒
1.
We consider the design of opportunistic spectrum access (OSA) strategies that allow secondary users to search for and exploit spectrum opportunities in unslotted primary systems. The traffic of the primary system in each channel is modeled by a continuous time Markov process. We formulate the joint design of OSA as a constrained discrete-time partially observable Markov decision process (POMDP). A separation principle for the joint design of OSA is established under certain conditions on the probability of false alarm of the spectrum sensor. This result extends the separation principle for OSA in slotted primary systems to unslotted primary systems. Furthermore, we show that the myopic sensing policy has a simple and robust structure under certain conditions on the probability of false alarm. 相似文献
2.
Weijian Liu Jun Liu Lei Huang Qinglei Du Yong-Liang Wang 《Journal of The Franklin Institute》2019,356(1):629-653
For multichannel signal filtering or detection in unknown noise, it is usually difficult to obtain sufficient independent and identically distributed (IID) training data in real-world applications, which considerably degrades the performance of adaptive algorithms. In this paper, we consider the problem of subspace signal filtering and detection in sample-starved environment. A simple reduced-dimension approach is adopted, which alleviates the requirement of IID training data. First, the test and training data are projected onto the signal subspace. Then we adopt the criterion of the generalized likelihood ratio test (GLRT) to devise a detector, which can also serve as a filter. The resulting detector can properly work in sample-starved environment, where the number of IID training data is less than the dimension of the test data. Moreover, the devised approach is superior to the existing adaptive subspace processor in filtering and detection, even in some sample-abundant situations. Analytical expressions for the probabilities of detection and false alarm are derived for the proposed approach. Numerical examples are given to verify its effectiveness. 相似文献
3.
Huifang Min Shengyuan Xu Yongmin Li Yuming Chu Yunliang Wei Zhengqiang Zhang 《Journal of The Franklin Institute》2018,355(5):2645-2661
This paper is devoted to the adaptive finite-time control for a class of stochastic nonlinear systems driven by the noise of covariance. The traditional growth conditions assumed on the drift and diffusion terms are removed through a technical lemma, and the negative effect generated by unknown covariance noise is compensated by combining adaptive control technique with backstepping recursive design. Then, without imposing any growth assumptions, a smooth adaptive state-feedback controller is skillfully designed and analyzed with the help of the adding a power integrator method and stochastic backstepping technique. Distinctive from the global stability in probability or asymptotic stability in probability obtained in related work, the proposed design algorithm can guarantee the solution of the closed-loop system to be finite-time stable in probability. Finally, a stochastic simple pendulum system is skillfully constructed to demonstrate the effectiveness of the proposed control scheme. 相似文献
4.
Mohamed B. El Mashade 《Journal of The Franklin Institute》2005,342(5):521-550
The radar signals returning from the targets being illuminated are usually accompanied by thermal noise and clutter. Constant false alarm rate (CFAR) processors are useful for detecting these targets in a background for which the parameters of the statistical distribution are not known and may be nonstationary. The ordered-statistics (OS) CFAR technique has been proven to work satisfactorily in both multiple-target and nonuniform clutter cases. Unfortunately, the large processing time taken by this scheme limits its practical uses. The modified versions of the OS processor have been proposed to replace it in these applications. They can reduce the processing time of the single-window OS detector in half without changing its useful properties. Our goal in this paper is to provide a complete detection analysis for the OS processor along with ordered-statistic greatest-of (OSGO) and ordered-statistic smallest-of (OSSO) modified versions, for M postdetection integrated pulses when the operating environment is nonideal. Analytical results of performance are presented in both multiple-target situations and in regions of clutter power transitions. The primary and the secondary interfering targets are assumed to be fluctuating in accordance with the Swerling II target fluctuation model. As the number of noncoherently integrated pulses increases, lower threshold values and consequently better detection performances are obtained in both homogeneous and multiple-target background models. However, the false alarm rate performance of OSSO-CFAR scheme at clutter edges worsens with increasing the postdetection integrated pulses. As predicted, the OSGO-CFAR detector accommodates the presence of spurious targets in the reference window, given that their number is within its allowable range in each local window, and controls the rate of false alarm when the contents of the reference cells have clutter boundaries. The OSSO-CFAR scheme is useful in the situation where there is a cluster of radar targets amongst the estimation cells. 相似文献
5.
分析了中高分辨率SAR海洋图像的目标和海杂波特点. 利用舰船目标的灰度相关性和形状特性与背景杂波的差异,提出了一种基于独立联合K-分布CFAR的舰船检测算法. 算法建立了海杂波的二维独立联合K-分布概率模型,通过给定的虚警率得到检测阈值以对图像进行检测. 该算法能够极大地抑制斑点噪声和背景局部不均匀对检测带来的影响,有效地降低了虚警数,检测效果得到了明显改善. 相似文献
6.
扩展频水印技术是一种鲁棒的水印算法 .如何提高扩频水印算法的鲁棒性是当前一大研究热点 .充分利用图象的像素与其周围像素之间的差值的统计特性 ,利用差调制的方法嵌入水印信息 ,从而降低了原始图象对该水印算法鲁棒性的影响 ,来提高水印算法的鲁棒性 .理论分析表明 ,该算法可以同时获得较小的误警和误拒概率 ,从而表明该算法有较好的性能 .实验结果表明 ,该算法可以鲁棒地抵抗常用的攻击 ,如JPEG压缩、中值滤波、加噪声和图象大小调整 . 相似文献
7.
Peng Yun Panlong Wu Xingxiu Li Shan He Kai Wu 《Journal of The Franklin Institute》2021,358(8):4503-4527
For target tracking systems, the probability of detecting a target is difficult to determine, and the process noise often has non-Gaussian heavy-tailed characteristics owing to interference from outliers. To address the issues associated with single target tracking within clutters in scenarios with an unknown detection probability and heavy-tailed process noise, this paper presents a variational Bayesian-based adaptive probabilistic data association filter (VB-APDAF). The beta distribution, Pearson type VII distribution and multinomial distribution are used to model the detection probability, the process noise, and the association events, respectively. To guarantee the conjugation, a novel parameter estimation strategy is employed. In this strategy, the previous state is introduced in the state update process to construct the joint probability density function of parameters to be estimated and data set. The VB framework is used to estimate the target state, detection probability, and associated events. An experiment was performed under simulated conditions to demonstrate the effectiveness of the proposed filter. 相似文献
8.
在超宽带穿墙雷达压缩感知成像中,常常使用Rademacher序列作为模拟信息转换器的chipping序列。而这种序列的功率谱类似于高斯白噪声的功率谱,它与回波信号的功率谱不匹配,导致低速采样前信号的信噪比偏低,最终影响了成像效果。文章从低速采样前的平均信噪比最大化入手,构建设计匹配chipping序列的优化算法以导出其成立的条件,给出一种使用马尔科夫链游程长度受限(RLL)序列来设计匹配chipping序列的解决方案。仿真结果表明,使用马尔科夫链RLL序列设计匹配chipping序列的成像结果优于Rademacher序列,其图像的信噪比提高2~3dB。 相似文献
9.
This paper addresses the problem of global finite-time adaptive control for a class of switched stochastic uncertain nonlinear systems under arbitrary switchings. By applying the delicate introduction of coordinate transformations and adding a power integrator technique, an adaptive controller is constructed to guarantee that the system state is regulated to the origin almost surely in a finite time while maintaining the boundedness of the resulting closed-loop systems in probability. Two examples are given to illustrate the effectiveness of the proposed control scheme. 相似文献
10.
《Journal of The Franklin Institute》2021,358(16):8772-8785
Conventional grant-based random access scheme is inappropriate to massive Internet of Things (IoT) connectivity since massive devices results in large number of collisions. This is unacceptable for the low latency requirement in 5 G and future networks. It is also not possible to assign orthogonal pilot sequences to all users to perform user activity detection (UAD) due to the massive number of devices and limited channel coherence time. In this paper, a novel grant-free (GF) UAD scheme is proposed with extremely low complexity and latency in an IoT network with a massive number of users. We exploit multiple antennas at the base station (BS) to produce spatial filtering by a fixed beamforming network (FBN), there then the inter-beam interference can be mitigated. Moreover, intra-beam interference is removed in temporal domain by orthogonal multiple access (OMA) technology. Joint UAD and multiuser detection (MUD) is realized by a bank of spatial-temporal matched filters at BS. The proposed method is efficient and the complexity is much less than the existing compressed sensing (CS)-based GF non-orthogonal multiple access (GFNOMA) algorithms. Performances of the proposed method is extensively analyzed in terms of the successful activity detection rate (SADR) as well as the Receiver operating characteristic (ROC) based on Neyman-Pearson (NP) decision rule. Numerical results demonstrate that it is comparable to the recently proposed iterative Maximum Likelihood (ML) algorithm, yet the computation load of the proposed scheme is extensively reduced. 相似文献
11.
《Journal of The Franklin Institute》2022,359(18):10510-10524
This paper investigates the problem of finite-time attack detection for nonlinear complex cyber-physical networks under false data injection (FDI) attacks. Firstly, a Takagi-Sugeno (T-S) fuzzy model is used to approximate nonlinear complex cyber-physical networks in which the measurement channels are injected by FDI attacks. Secondly, based on adding a power integrator technique, a finite-time fuzzy observer is designed to achieve the rapid state observation of complex cyber-physical networks within a finite time by adjusting the observer parameters. Then, an attack detection mechanism consisting of the finite-time fuzzy observer and an attack detector is developed to detect FDI attacks, which can trigger an alarm within a finite time when FDI attacks occur. Finally, simulation results are given to show the effectiveness and superiority of the proposed method. 相似文献
12.
漏钢报警系统对于连铸工艺现场事故预报有着至关重要的作用,通过动态逻辑判断法改善现场工艺缺陷,提高预报的准确性。新报警系统的应用取得了很好的效果,对比达涅利公司报警系统漏钢误报率显著下降。新系统的改进将报警率降低至32次/月,保证了生产稳定与铸坯质量。 相似文献
13.
由于无线网路中链路质量的不稳定、信号的广播传输模式和节点之间存在的相互干扰，针对提高无线网状网络性能的信道分配和路由选择将更加复杂。采用多信道成为一种可选的提高网络容量的方法。本文提出了一种基于2.4GHz 802.11无线网状网络的一种固定信道分配方法，采用了多输入多输出技术使得网络中的数据流以流水线的方式进行传输。在这个场景下多条并行的流可以同时被激活，以此来提升UDP和TCP的传输性能。通过对802.11b网络中1、6和11三个相互不重叠的信道的分配，该信道分配算法在空间上实现邻居节点之间的干扰最小化，其中信道1和11被分配给网状网络的主干传输部分，信道6被分配给用户接入网络。文章最后通过NS2仿真实验，并对本文提出的算法进行了分析。实验结果证明网络的平均吞吐率有大幅度提升，且多跳传输的延迟也被降低。 相似文献
14.
15.
Andreas M. Maras 《Journal of The Franklin Institute》2005,342(5):565-581
In this paper, a new approach to non-parametric signal detection with independent noise sampling is presented. The present approach is based on the locally asymptotically optimum (LAO) methodology, which is valid for vanishingly small signals and very large sample sizes, and on semi-parametric statistics. Its unique feature and essential difference from other techniques is that LAO non-parametric detectors are optimum according to the Neyman-Pearson criterion by being asymptotically uniformly most powerful at false alarm level α (AUMP (α)) and adaptive in the sense that no loss in Fisher's information number is incurred when the underlying noise process is no longer parametrically defined. Accordingly, they are robust against deviations from the postulated noise model and, unlike other non-parametric detectors, are distribution-free under both hypotheses H0 (“noise only present”) and H1 (“signal and noise present”). Non-parametric LAO detectors are derived from an asymptotic stochastic expansion of the log-likelihood ratio for coherent and narrowband incoherent “on-off” signals. Moreover, under the present framework it is shown that, in direct contrast to already known results, the non-parametric sign detector is AUMP (α) and adaptive even for non-constant signal samples. 相似文献
16.
《Journal of The Franklin Institute》2007,344(3-4):243-256
A new pre-processing method for colour fundus images with adaptive contribution of the red channel is proposed. Based on a condition that is developed in this paper, this method utilises the intensity information from both red and green channels instead of using only the green channel as in the usual practice. The histogram matching is used to modify the histogram of the green channel by using the histogram of the red channel (of the same retinal image) to obtain a new processed image having the advantages of both channels. This method can be used to correct non-uniform illumination in colour fundus images or as a pre-processing step in the automatic analysis of retinal images.Results show that the use of histogram matched (HM) image give better performance than using the green channel image when employing the two-dimensional matched filter to detect retinal blood vessels. At specificity of 90%, in case of abnormal images, sensitivity increased from 76% when using the green channel image to 82% when using the HM image compared with 81% when using the piece-wise threshold probing method. In case of normal images, at the same specificity, the sensitivity obtained when using green channel image or HM image was 87% compared with 88% for the piece-wise threshold probing method. 相似文献
17.
Evaluation of fault diagnosability for networked control systems subject to missing measurements 总被引：1，自引：0，他引：1
The evaluation of fault diagnosability for networked control systems subject to missing measurements is addressed in this paper. In particular, the missing probability is assumed to be affected by norm-bounded uncertainties. By considering noise and missing measurements, the quantitative diagnosability problem is investigated via the principle of weight. To quantify the effect of uncertain missing probabilities, an interval criterion is presented and uncertainty ratio is defined. Furthermore, a novel method is proposed to alleviate the computation task of evaluating fault diagnosability. The effectiveness of the proposed method is verified by a numerical example. 相似文献
18.
This paper is concerned with the security control problem for a class of Markov jump systems subject to false data injection attack and incomplete transition rates. An on-line estimation strategy is provided for the time-variant and unknown cyber-attack modes. And then, an adaptive sliding mode controller is synthesized with different robust terms for different modes to guarantee the reachability of the specified sliding surface. Moreover, the sufficient conditions for the stability of the closed-loop systems are derived. Finally, it is shown from simulation results that the effect of both false data injection attack and incomplete TRs can be effectively attenuated by the present adaptive SMC method. 相似文献
19.
论文以低轨卫星信道为例，给出一种适用于大频偏条件下突发通信系统直接扩频序列混合并行捕获结构，分析了预检测积分时间和判决门限对平均捕获时间的影响，提出了在门限信噪比下以平均捕获时间最小为原则的预检测积分时间和判决门限参数最优设置方案。 相似文献
20.
Yun Feng Yaonan Wang Jun-Wei Wang Han-Xiong Li 《Journal of The Franklin Institute》2021,358(2):1656-1672
Detection and estimation of abnormalities for distributed parameter system (DPS) have wide applications in industry, e.g., battery thermal fault diagnosis, quality monitoring of hot-rolled strip laminar cooling process. In this paper, the abnormal spatio-temporal (S-T) source detection and estimation problem for a linear unstable DPS is first studied. The proposed methodology consists of two steps: first, an abnormality detection filter (ADF) which generates a residual signal for abnormality detection in the time domain is constructed using pointwise measurement; Then, an adaptive Luenberger-type PDE observer including an adaptive estimation algorithm is designed and triggered only when an alarm raises from the ADF. Theoretic analysis based on the spatial domain decomposition approach is presented to show the convergence of the estimation errors. Finally, an illustrative example is presented to show the performance of the proposed method. 相似文献