Infornation Modeling and Analysis of Event Related Potentials

An approach to the analysis of event related potentials (ERP) based on information theory is described. The amount of information in cortical potentials evoked by words briefly presented by tachistoscope is measured by a transinformation method. The inputs to the communication channel are four word categories. One category is composed of pleasant words, another of unpleasant words, both drawn from the Osgood semantic differential research, and two categories are composed of word stimuli related to a psychiatric patient's complaints. The patients chosen for study exhibit either phobias or pathological grief reactions. The method allows ERP's to be mapped into transinformation profiles that reveal time intervals during the poststimulus ERP favorable to the transmission of information concerning the word category presented. The transinformation model results for actual and synthetic data are discussed.     

实现线性约束最小功率滤波器的迭带辅助矢量算法

本文从不同的角度推广了基于辅助矢量的迭带最小功率无失真响应滤波器(IMPDR-AVF).通过推广滤波器的优化设计准则,得到了迭带线性约束最小功率滤波器(ILCMP-AVF).研究表明此算法是优化理论中Rosen梯度投影法的一种特例.通过推广加权系数的设计准则,提出了基于局部最优准则的ILCMP-LOC滤波器,其收敛速度快于ILCMP-AVF.与采样矩阵逆(SMI)算法相比,在计算量几乎不变的情况下,当辅助矢量个数在很大的范围内选择时,ILCMP-LOC和ILCMP-AVF算法的自适应性能均优于SMI算法.本文以阵列信号处理中的干扰抑制为例分析了这些算法的性能.     

一种基于M-Z干涉仪的事件识别算法

利用基于马赫-曾德尔(M-Z)干涉原理的分布式光纤振动传感监测系统,提出了一种光缆振动事件的识别方法。该方法解决了普通光纤振动传感监测系统不具备模式识别智能分析可操作性的问题。通过对光缆上的振动事件的分析对振动的事件识别建模,利用大量实验数据将振动事件分类,通过与这些振动事件的比较,实现对振动事件的识别。     

迭代迫零多用户检测算法研究与应用

最优的最大似然多用户接收机的复杂度随用户数成指数增长,传统的Rake接收机干扰受限且存在远近效应。次优的线性多用户检测是性能和复杂度的折衷,其中,迫零联合检测多用户接收机属于一种线性解相关接收机,虽然避免了对数据符号矢量的穷举搜索,大大减少了计算量,但是由于其基本运算中包含了随机矩阵的求逆运算,而矩阵求逆运算对于硬件定点实现的舍入误差非常敏感,有时会产生很大的误差甚至无解。考察比较了迫零检测接收机的四种迭代算法。对其复杂度进行了分析和仿真,结果表明Gauss-Siedel是一种收敛速度较快,时间复杂度较低的迭代算法。     

Iterative Single-Antenna Interference Cancellation: Algorithms and Results

The capacity of cellular mobile communication systems can significantly be improved using single-antenna interference cancellation (SAIC) techniques. This paper analyzes several soft-input–soft-output (SISO) detectors in iterative SAIC receivers based on the turbo principle and compares their performances and complexities. Among them, the concurrent maximum a posteriori probability (MAP) receiver, which detects single-user signals and exchanges the soft information between cochannel users, is found to provide a good balance between performance and complexity. It can perform nearly the same as the joint MAP algorithm and achieve the single-user matched-filter bound (MFB), and its complexity only linearly increases with the number of cochannel signals. Other reduced-complexity algorithms, such as the Rake Gaussian (RG) approach and soft interference cancellation with MAP equalization (SIC-MAP), also achieve satisfactory performance for binary phase-shift keying (BPSK) modulation when the cochannel interference (CCI) signal can be decoded.      

水下数字图像盲复原算法研究

图像复原的目的是从观测到的退化图像重建原始图像,它是图像处理、模式识别、机器视觉等的基础。盲复原作为其中一个重要分支,其主要思想是在点扩展函数未知的情况下,力求获得最佳的清晰效果。由于水下图像退化模型中点扩展函数一般为高斯模型,故针对此提出误差一参数估计法,根据图像退化过程,给出频率域的误差形式,并选定参数的变化范围,再利用复原算法做出误差参数曲线,由此估计出点扩展函数的参数值,最后利用经典的复原算法,如维纳滤波对退化图像进行复原。实验证明该方法获得了比较清楚的复原效果。     

语音增强算法综述及性能分析

语音增强是解决噪声污染的一种有效手段,其主要目标就是从带噪语音中尽可能地提取纯净语音,目前已发展为语音信号处理的一个重要分支,在实际中具有重要价值.实际中经常用到的算法主要有谱减法、维纳滤波、基于统计模型的增强算法(如MMSE)和子空间法.主要介绍谱减法、MMSE、两步消噪(TSNR)和子空间法的算法基本原理,并采用客观评价指标对四种典型算法的降噪效果进行比较和分析.     

基于迭代滤波盲复原算法的水下图像噪声去除

摘要：图像复原的目的是从观测到的退化图像重建原始图像,维纳滤波与约束去卷积滤波是比较常采用的复原方法。在未知降质函数的情况下,直接运用维纳滤波和约束去卷积滤波有一定困难。针对此提出以维纳滤波与约束去卷积滤波为模型的迭代滤波盲复原算法对水下图像进行去噪。实验证明,该方法获得了比较理想的复原效果。     

Multichannel, Single Tral Event Related Potential Classification

We report on the effect of electrode placement and number of electrodes on the classification of single trial event related potentials (ERP's). The subjects read propositions relating fictitious people and their occupations while ERP's were recorded. The subjects decided if the proposition was correct or incorrect and responded as per instructions. The single trial, multichannel ERP data were classified using various methods, e. g., hold-out, leave-one-out, resubstitution. Several other factors were examined to determine their effect on ERP classification, including taking a majority vote among channels, using the single best channel, and averaging the data across channels for a single ERP. The results from other experiments are compared to those presented here.     

高性能语音增强算法的研究

讨论在强噪声环境下语音增强的新方法,即将主从结构的自适应滤波算法与级联谱相减算法相结合的方法。计算机仿真结果表明,该方法在大大消除背景噪声的同时,消除了“音乐噪声”,同时保证了较好的语音可懂度。     

Majorization–Minimization Algorithms for Wavelet-Based Image Restoration

Standard formulations of image/signal deconvolution under wavelet-based priors/regularizers lead to very high-dimensional optimization problems involving the following difficulties: the non-Gaussian (heavy-tailed) wavelet priors lead to objective functions which are nonquadratic, usually nondifferentiable, and sometimes even nonconvex; the presence of the convolution operator destroys the separability which underlies the simplicity of wavelet-based denoising. This paper presents a unified view of several recently proposed algorithms for handling this class of optimization problems, placing them in a common majorization-minimization (MM) framework. One of the classes of algorithms considered (when using quadratic bounds on nondifferentiable log-priors) shares the infamous ldquosingularity issuerdquo (SI) of ldquoiteratively re weighted least squaresrdquo (IRLS) algorithms: the possibility of having to handle infinite weights, which may cause both numerical and convergence issues. In this paper, we prove several new results which strongly support the claim that the SI does not compromise the usefulness of this class of algorithms. Exploiting the unified MM perspective, we introduce a new algorithm, resulting from using bounds for nonconvex regularizers; the experiments confirm the superior performance of this method, when compared to the one based on quadratic majorization. Finally, an experimental comparison of the several algorithms, reveals their relative merits for different standard types of scenarios.     

Iterative Algorithms for Performance Evaluation of Wireless Networks with Guard Channels

Analytical and modeling work performed since the late eighties have led to nonlinear equations that relate important parameters used for performance evaluation of wireless networks. These nonlinear equations have no closed-form solution and iterative algorithms are used to find numerical solutions. However, iterative algorithms that are not designed to detect and overcome nonconvergence situations may fail to converge. We present an iterative algorithm that numerically solves six dependent nonlinear equations. The algorithm always converges and obtains values of blocking probability, p_b, and forced termination probability, p_ft, at any desired level of accuracy. We then used this algorithm to numerically show that for a given pair of values of p_b and p_ft, there is an optimal number of guard channels that supports a maximal new-call arrival rate.     

两种稀疏孔径光学成像的图像恢复算法研究

根据稀疏孔径光学系统成像的图像恢复模型,分析维纳滤波和最小二乘方滤波图像恢复算法的适用条件.针对存在噪声干扰的稀疏孔径光学系统,维纳滤波的理论推导能够达到最优.通过实验对比,指出噪声功率谱未知情况,最小二乘方滤波的恢复结果优于维纳滤波结果.     

Adaptive Parallel and Iterative QRDM Detection Algorithms for MIMO Multiplexing Systems

QR-decomposition with M-algorithm (QRDM) achieves quasi-ML performance in multiple-input multiple-output (MIMO) multiplexing systems. Nevertheless, QRDM performs avoidable computations because of its systematic search strategy and its failure to consider the channel and noise conditions. Another drawback is that QRDM is sequential, which limits pipelining capabilities. In this paper, we propose quasi-ML adaptive parallel QRDM (APQRDM) and adaptive iterative QRDM (AIQRDM) algorithms based on set grouping. In set grouping, the tree-search stage of the QRDM algorithm is divided into partial detection phases (PDPs). These are processed in parallel and iteratively in the proposed APQRDM and AIQRDM algorithms, respectively. Therefore, when the tree-search stage of the QRDM algorithm is divided into G PDPs, the latency of the proposed APQRDM algorithm and the hardware requirements of the proposed AIQRDM algorithm are reduced by a factor of G compared to the QRDM algorithm. Moreover, simulation results show that in 4?×?4 MIMO system, and at E _b /N ₀ of 12?dB, APQRDM decreases the average computational complexity to approximately 43% that of the conventional QRDM. Also, at E _b /N ₀ of 0?dB, AIQRDM algorithm reduces the computational complexity to about 54%, and the average number of metric comparisons to approximately 10%, compared to the conventional QRDM.     

Steady-State Movement Related Potentials for Brain–Computer Interfacing

An approach for brain-computer interfacing (BCI) by analysis of steady-state movement related potentials (ssMRPs) produced during rhythmic finger movements is proposed in this paper. The neurological background of ssMRPs is briefly reviewed. Averaged ssMRPs represent the development of a lateralized rhythmic potential, and the energy of the EEG signals at the finger tapping frequency can be used for single-trial ssMRP classification. The proposed ssMRP-based BCI approach is tested using the classic Fisher's linear discriminant classifier. Moreover, the influence of the current source density transform on the performance of BCI system is investigated. The averaged correct classification rates (CCRs) as well as averaged information transfer rates (ITRs) for different sliding time windows are reported. Reliable single-trial classification rates of 88%-100% accuracy are achievable at relatively high ITRs. Furthermore, we have been able to achieve CCRs of up to 93% in classification of the ssMRPs recorded during imagined rhythmic finger movements. The merit of this approach is in the application of rhythmic cues for BCI, the relatively simple recording setup, and straightforward computations that make the real-time implementations plausible.     

指纹图像对比度模糊增强算法

指纹图像采集过程常会造成对比度不强等非线性失真,基于模糊逻辑的处理方法常用于改善指纹图像质量。研究了模糊特征平面增强算法和基于广义模糊算子的图像增强算法,将两种算法应用于指纹图像对比度增强,并对增强结果进行比较分析。实验结果表明,采用这2种方法均可以在一定程度上提高指纹图像低灰度区域和高灰度区域之间的对比度,从而提高图像的质量,使增强后的指纹图像结构更清晰。     

频域迭代盲解卷积图像恢复方法及其算法实现

详细讨论了一种新的模糊图像复原法 ,使用这种方法 ,不需知道图像模糊过程的模糊因子 ,就可以实现图像的恢复。该算法易于编程 ,且具有较强的通用性。分析了计算机算法 ,并给出了处理的结果。     

High-throughput VLSI Implementations of Iterative Decoders and Related Code Construction Problems

We describe an efficient, fully-parallel Network of Programmable Logic Array (NPLA)-based realization of iterative decoders for structured LDPC codes. The LDPC codes are developed in tandem with the underlying VLSI implementation technique, without compromising chip design constraints. Two classes of codes are considered: one, based on combinatorial objects derived from difference sets and generalizations of non-averaging sequences, and another, based on progressive edge-growth techniques. The proposed implementation reduces routing congestion, a major issue not addressed in prior work. The operating power, delay and chip-size of the circuits are estimated, indicating that the proposed method significantly outperforms presently used standard-cell based architectures. The described LDPC designs can be modified to accommodate widely different requirements, such as those arising in recording systems, as well as wireless and optical data transmission devices.