基于分数低阶统计量的盲多用户检测算法

多用户检测算法是抑制CDMA系统中多址干扰的重要手段,但广泛存在的非高斯信道噪声会降低以往的基于高斯噪声模型假设的算法性能.本文采用α稳定分布作为噪声模型,提出了基于分数低阶统计量的盲多用户检测算法,并对该算法进行了理论分析.仿真和分析表明,该算法具有很好的韧性,同时适用于高斯噪声和脉冲噪声环境.     

基于光子噪声研究光子探测器的探测性能

根据红外光子探测器的基本工作原理,分析了光电探测器性能的基本物理机理限制,推导了背景辐射的光子噪声限制下的比探测率。对背景限制下的比探测率随探测器截止波长、背景温度的变化进行了理论计算。对计算结果进行了理论分析,并作出了相应总结。最后提出了提高背景限制下比探测率的方法。     

A Universal Impulse Noise Filter with an Impulse Detector and Nonlocal Means

In this paper, we propose an efficient filter for universal impulse noise removal. Operation is carried out in two stages: impulse detection followed by filtering. For detection, a robust local image statistic, called the extremum compression rank-order absolute difference (ECROAD), is designed to detect impulse noise in an image. For filtering, a universal impulse noise filter is proposed by combining the ECROAD statistic with the nonlocal means (NLM). The inherited switching behavior will preserve image details by selecting possible “noise pixels” for processing. Meanwhile, the joint impulsive weight is able to avoid the effect of impulsive components in restoring candidates. Simulation results show that the proposed filter produces excellent results and outperforms most existing filters for different impulse noise models.     

Impulse Noise Performance Bounds for Binary Correlation Receivers

A general performance equation is derived for digital receivers in the presence of impulse noise. Two bounding techniques are employed to simplify the results. First, the Schwarz inequality removes the dependence on both the impulse noise waveforms and the signal-set basis functions. Second, the Chebyshev inequality is applied to the Schwarz results to additionally eliminate the statistical dependence on the probability density function of the noise waveform weighting factor. The bound curves are compared to specific theoretical results where the noise waveforms and probability density functions have been assumed. The tightness of the bound curves is a function of the signal-energy-to-noise-weighting-factor variance ratio and converges for the Schwarz bound as the ratio increases. Considerably looser bounds are obtained by the Chebyshev technique, but rough estimates of system performance can be obtained when the signalenergy-to-signal-energy-to-noise-variance ratio is the only known parameter.     

基于脉冲噪声中信号检测的模糊检测器

本文提出了一种基于脉冲噪声中信号检测的模糊检测器的设计方法。该方法将贝叶斯检测理论与通过样本数据学习到的关联模糊规则集中于一体，可改善系统的品质和适应能力，因而大大降低了信息符号的误差概率。数字仿真结果表明，对比传统的最大似然检测器和最优贝叶斯检测器，这种新型的模糊检测器取得了良好的控制效果。     

基于最小误差熵的有源脉冲噪声控制算法

有源噪声控制(ANC)基于相消干涉的原理,能够有效降低低频噪声的影响。传统的ANC方法为滤波x最小均方(FxLMS)算法,该算法由于结构简单、易于实现,在实际中得到广泛应用。FxLMS假设环境中的噪声属于高斯噪声,但是许多实际环境中的噪声呈现脉冲噪声的特点。FxLMS方法利用二阶矩,但是在脉冲环境中由于误差的方差不存在,因此传统的FxLMS算法降噪性能下降,甚至造成系统的不稳定。最小误差熵(MEE)自适应滤波算法对脉冲信号鲁棒,将其应用到ANC系统,提出Fx MEE算法以应对环境中的脉冲噪声。仿真结果表明提出的方法在不同脉冲环境下相比于现有的算法均能实现较好的降噪性能。     

Relative Intensity Noise Performance of Wavelength Converters Based on Four-Wave Mixing in Semiconductor Optical Amplifiers

We present a numerical and experimental study of the relative intensity noise (RIN) induced by the four-wave mixing (FWM) based wavelength conversion process in a semiconductor optical amplifier (SOA). The study is based on the RIN evaluation of the converted signal, under various operating conditions (input power levels and wavelength detuning) and input noise characteristics. A detailed numerical model is employed to simulate the FWM process, taking into account the amplified spontaneous emission (ASE) noise, the wavelength dependent gain, and the interaction of four waves in the SOA (two input waves and two product waves). It is shown that for low noise input signals, the output RIN is determined by the power levels of the pump and signal and the wavelength detuning. Operation under saturation allows reduction of the output RIN levels with respect to the input     

一种基于峰度系数的脉冲噪声检测算法的研究及其FPGA实现

针对激光测振系统中散斑效应导致的语音脉冲噪声,该文研究了一种基于4阶累积量的峰度检测算法,推导了峰度系数和归一化峰度系数的数学迭代公式,并在FPGA的实现中提出了一种峰度系数的动态阈值的判决方法.基于实验数据的仿真结果表明,该算法较理论公式减少了约25％的计算量,节省了硬件资源,对较小幅度的脉冲噪声具有更敏感的检测性能.     

基于神经网络噪声检测的自适应中值滤波器

针对椒盐噪声污染图像的滤波问题,提出了一种基于前馈神经网络的噪声检测器。基于这种噪声检测方法,采用自适应中值滤波算法,依据像素点的不同属性采用不同的滤波策略。实验结果表明,该算法在有效去除椒盐噪声的同时更好地保留了图像的边缘和细节,是一种有效的图像去噪方法。     

低噪声CMOS图像传感器的研究

近年来CMOS图像传感器在医疗和工业CT等领域中得到了越来越广泛的应用。作为CMOS图像传感器的前端处理电路,多通道积分器阵列的性能参数直接决定了传感器的成像质量并成为该领域的研究热点。本文的主要研究内容是低噪声探测器的研究。对芯片的测试结果表明,低噪声探测器的电路设计和版图设计均取得初步成功,基本达到预期的设计目标。     

一种基于峰度系数的脉冲噪声检测算法的研究及其FPGA实现

针对激光测振系统中散斑效应导致的语音脉冲噪声,该文研究了一种基于4阶累积量的峰度检测算法,推导了峰度系数和归一化峰度系数的数学迭代公式,并在FPGA的实现中提出了一种峰度系数的动态阈值的判决方法.基于实验数据的仿真结果表明,该算法较理论公式减少了约25％的计算量,节省了硬件资源,对较小幅度的脉冲噪声具有更敏感的检测性能...     

基于深度置信网络的随机脉冲噪声快速检测算法

为提高现有随机脉冲噪声(RVIN)检测算法的检测准确率和执行效率,该文试图从构建描述能力更强的特征矢量和训练非线性映射更为准确的预测模型两个方面入手,实现一种基于训练策略的快速RVIN检测算法。一方面,提取多个不同阶的对数绝对差值排序统计值并结合一个能够反映图像边缘特性的统计值作为刻画图块中心像素点是否为噪声的特征矢量。在计算量增加极少的情况下,显著提升了特征矢量的描述能力。另一方面,基于深度置信网络(DBN)训练RVIN预测模型(RVIN检测器)将特征矢量映射为噪声类型标签,实现了比浅层预测模型更为准确的映射。大量实验数据表明：与现有的RVIN检测算法相比,所提算法在检测准确率和执行效率两个方面都更有优势。

     

Envelope Detector Performance for a Partially Coherent-Fading Sine Wave in Noise

The performance of a matched filter square-law envelope detector is investigated for a new signal-in-noise model, that of a partially coherent-fading random-phase sine wave in additive zero-mean noise. This model is of interest when analyzing the effects of random amplitude and/or phase channels on narrow-band input signals. The amplitude and the phase of the sine wave are assumed to be independent random processes with known bandwidths. This paper obtains deflection-criteria detection-performance results for the envelope detector as a function of the bandwidths of the amplitude and phase of the signal process, the noise process, the observation time, and the second-moment statistics of the amplitude, phase, and noise processes. The results show quantitatively that the detection performance of the envelope detector is much more sensitive to loss of phase coherence than to loss of amplitude coherence.     

对含脉冲噪声的图像去噪算法的研究

在传统均值滤波和中值滤波的基础上,结合聚类算法理论,采用硬聚类算法和模糊模型两种算法消除图像中的脉冲噪声。与传统的滤波算法和硬聚类模型去噪算法相比,基于模糊模型的去噪算法更好地提高了图像的清晰度和信噪比。     

Comments on "Envelope Detector Performance for a Partially Coherent-Fading Sinewave in Noise"

The basic premise in a recent paper that the matchedfilter square-law envelope detector is generally appropriate for fastfading as well as slow-fading incoherent channels is questioned. Its inappropriateness for a fast-fading incoherent Gaussian channel is demonstrated by evaluation of probability of error for this receiver and for the optimum receiver. As a result, modifications to some of the conclusions drawn regarding attainable performance gain with increasing observation time are proposed. In addition, it is pointed out that the performance predictor adopted, viz., deflection, exhibits anomalous behavior (for at least some incoherent fading channels), thereby rendering the other conclusions questionable.     

基于OPNET的网络仿真与性能测量

网络仿真在今天的通信与网络领域是一个非常重要的技术手段.文章介绍了OPNET的建模层次和建模方法,给出了OPNET进行网络仿真的步骤,并利用OPNET对一个局域网进行了仿真并对相关性能进行了测量,为优化网络设计提供了重要的依据.     

脉冲噪声模拟器校准方法

本文主要介绍了脉冲噪声模拟器的一种校准方法。     

Impulse Noise Correction in OFDM Systems

In orthogonal frequency division multiplexing (OFDM) systems, the impulse noise causes catastrophic accuracy degradation since the impulse noise affects all the subcarriers in a symbol due to the fast Fourier transform (FFT) operations at the receiver. Potential causes of impulse noise include erasure channel, power switching, and circuit failure in integrated circuits. In this paper, from a practical observation, a novel iterative impulse error correction scheme is proposed. This scheme is referred to as the impulse noise location and value search algorithm, which is based on the crucial observation of the relationship of the impulse noise and the symbol constellation. In a 512-FFT OFDM system at 25 dB additive white Gaussian noise signal-to-noise ratio, for quadrature amplitude modulation (QAM)-4 and QAM-8 modulation, simulation results show that our proposed novel scheme can effectively correct impulse errors that corrupt up to 20.7 % and 13.9 % of the received time-domain signal at known locations. In addition, without the knowledge of impulse noise location, the proposed scheme still can correct at least 9.96 % of the received time-domain signal for QAM-4 modulation.     

脉冲噪声下的时间延迟估计方法研究

针对室内脉冲噪声居多的情况,提出了一种根据噪声的分布特性,选用不同算法来实现时延估计.这里时延估计算法包括基于分数低阶和二阶统计量的方法.由于脉冲噪声服从低阶分布,采用分数低阶协方差方法.可以得到较好的时延估计精度及良好抗噪声能力和抗混响能力,比较适合室内的语音源定位.