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NONSTATIONARY LEARNING CHARACTERISTICS OF THE LMS ALGORITHM

IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS 1987年第10期34卷 1199-1207页

作者： GARDNER, WA Signal and Image Processing Laboratory Department of Electrical and Computer Engineering University of California Davis USA

Upper and lower bounding first-order linear recursions for the mean-squared error realized with the LMS algorithm subjected to a sequence of independent nonstationary training vectors are derived. These bounds coincide to give the exact evolution of mean-squared error for the problem of identification of a nonrecursive time-varying system with white-noise excitation. This leads to an exact formula for time-averaged mean-squared error that is used to study optimization of the step-size parameter for minimum time-average misadjustment. New results on dependence of the minimal step size and the minimum misadjustment on the degree of nonstationarity are obtained.

关键词： Least squares approximation System identification Adaptive filters Algorithm design and analysis Vectors Time varying systems Gaussian distribution Signal processing image processing

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REAL-VALUED FAST FOURIER-TRANSFORM ALGORITHMS

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IEEE TRANSACTIONS ON ACOUSTICS SPEECH AND SIGNAL processing 1987年第6期35卷 849-863页

作者： SORENSEN, HV JONES, DL HEIDEMAN, MT BURRUS, CS Department of Electrical and Computer Engineering Rice University Houston TX USA Digital Image Processing Laboratory Lockheed Missiles and Space Company Incorporated Palo Alto CA USA

This tutorial paper describes the methods for constructing fast algorithms for the computation of the discrete Fourier transform (DFT) of a real-valued series. The application of these ideas to all the major fast Fourier transform (FFT) algorithms is discussed, and the various algorithms are compared. We present a new implementation of the real-valued split-radix FFT, an algorithm that uses fewer operations than any other real-valued power-of-2-length FFT. We also compare the performance of inherently real-valued transform algorithms such as the fast Hartley transform (FHT) and the fast cosine transform (FCT) to real-valued FFT algorithms for the computation of power spectra and cyclic convolutions. Comparisons of these techniques reveal that the alternative techniques always require more additions than a method based on a real-valued FFT algorithm and result in computer code of equal or greater length and complexity.

关键词： Fast Fourier transforms Discrete Fourier transforms Signal processing algorithms Convolutional codes Discrete transforms Application software Algorithm design and analysis NASA Digital images

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RECURSIVE BLOCK CODING - A NEW APPROACH TO TRANSFORM CODING

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IEEE TRANSACTIONS ON COMMUNICATIONS 1986年第2期34卷 161-179页

作者： FARRELLE, PM JAIN, AK Signal and Image Processing Laboratory Department of Electrical and Computer Engineering University of California Davis CA USA

The concept of fast KL transform coding introduced earlier [7], [8] for first-order Markov processes and certain random fields has been extended to higher order autoregressive (AR) sequences and practical images yielding what we call recursive block coding (RBC) algorithms. In general, the rate-distortion performance for these algorithms is significantly superior to that of the conventional block KL transform algorithm. Moreover, these algorithms permit the use of small size transforms, thereby removing the need for fast transforms and making the hardware implementation of such coders more appealing. This improved performance has been verified for practical image data and results in suppression of the block-boundary effect commonly observed in traditional transform coding techniques. This is illustrated by comparing RBC with cosine transform coding using both one- and twodimensional algorithms. Examples of RBC encoded images at various rates are given.

关键词： Transform coding Karhunen-Loeve transforms Block codes Data compression image coding Signal processing image processing Bit rate Markov processes Rate-distortion

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ON THE SPECTRUM OF PSEUDO NOISE

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PROCEEDINGS OF THE IEEE 1986年第4期74卷 608-609页

作者： GARDNER, WA CHEN, CK Signal and Image Processing Laboratory Department of Electrical and Computer Engineering University of California Davis CA USA

Although the magnitude of the discrete Fourier transform of a maximal-length shift-register sequence is flat, except for its value at zero frequency, the higher resolution spectral content given by the Fourier-series transform is highly erratic. This little-known fact is described, and its ramifications on fast Fourier transforms of one-digit-extended pseudo noise and zero-padded pseudo noise are explained.

关键词： Discrete Fourier transforms Autocorrelation Frequency Interpolation Fourier transforms White noise Fast Fourier transforms Prediction algorithms Fourier series Signal processing

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THE ROLE OF SPECTRAL CORRELATION IN DESIGN AND PERFORMANCE ANALYSIS OF SYNCHRONIZERS

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IEEE TRANSACTIONS ON COMMUNICATIONS 1986年第11期34卷 1089-1095页

作者： GARDNER, WA Signal and Image Processing Laboratory Department of Electrical and Computer Engineering University of California Davis CA USA

The popular class of synchronizers that consist of a quadratic nonlinearity followed by a phase-lock loop is investigated, and it is shown that the optimum design of the quadratic transformation is characterized in terms of a spectral correlation function for the signal to be synchronized to. It is also shown that the SNR performance of this quadratic transformation, and the mean-square phase jitter of the phaselock loop are both characterized in terms of spectral correlation functions. The conditions under which the optimum quadratic transformations, for symbol synchronization of BPSK, QPSK, SQPSK, and MSK, and for carrier synchronization of BPSK, reduce to the well-known matched-filter-squarer are identified. In addition, the well-known zeromean-square-phase-jitter condition is generalized from PAM to all synchronizable signals, and is characterized in terms of the spectral correlation function. The low-SNR maximum-likelihood synchronizer for all quadratically synchronizable signals is characterized in terms of a multiplicity of maximum-SNR quadratic spectral-line generators. A closed form implementation in terms of a matched filter, squarer, and symbol-rate-synchronized averager is obtained for BPSK and QPSK signals.

关键词： Performance analysis Frequency synchronization Binary phase shift keying Quadrature phase shift keying Timing Jitter Signal generators Matched filters Oscillators Clocks

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ZERO CROSSINGS, BANDWIDTH COMPRESSION, AND RESTORATION OF NONLINEARLY DISTORTED BAND-LIMITED SIGNALS

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS image SCIENCE AND VISION 1986年第5期3卷 651-654页

作者： MARVASTI, F JAIN, AK Computer Vision and Image Processing Laboratory Department of Electrical and Computer Engineering University of California at Davis Davis California 95616 USA

This paper discusses the relationship between the zero crossings or zeros of band-limited signals and their nonlinear transformations. It is proved that the bandwidth of a signal can be compressed by a ratio of 1/ n if and only if the signal has n th-order zero crossings or zeros (if complex). Also, a monotonic nonlinearity in the observation of a band-limited signal can be identified from the zero crossings (or zeros) of the derivative of the observed signal. (The results are for one-dimensional signals. Extensions to two-dimensional signals remain to be addressed.)

关键词： Coherent systems Distortion Electronic imaging Imaging systems Modulation Phase shift

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Ray tracing parametric surface patches utilizing numerical techniques and ray coherence 86

Ray tracing parametric surface patches utilizing numerical t...

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13th Annual Conference on computer Graphics and Interactive Techniques, SIGGRAPH 1986

作者： Joy, Kenneth I. Bhetanabhotla, Murthy N. Signal and Image Processing Laboratory Computer Science Division Department of Electrical and Computer Engineering University of California Davis United States

ISBN: (纸本)0897911962

A new algorithm for ray tracing parametric surface patches is presented. The method uses quasi-Newton iteration to solve for the ray/surface intersection and utilizes ray-to-ray coherence by using numerical information from adjoining rays as initial approximations to the quasi-Newton algorithm. Techniques based upon object space subdivision are used to insure convergence to the correct intersection point. Examples are given of the use of the algorithm in scenes containing Bézier surface patches. Results show that a significant number of ray/surface intersections on these parametric surface patches can be found using very few iterations, giving a significant computational savings. © 1986 ACM.

关键词： Ray tracing

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FIR Anisotropic filters for image enhancement

FIR Anisotropic filters for image enhancement

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International Conference on Acoustics, Speech, and Signal processing (ICASSP)

作者： V. Algazi Signal and Image Processing Laboratory Department Electrical and Computer Engineering University of California Davis USA

This paper describes a technique for the enhancement of images by FIR filters which compensates for the decreased response of human vision at high spatial frequencies. Because many images contain mainly horizontal and vertical features, and because vision is less acute along diagonals, it is possible to design anisotropic enhancement filters which do not increase greatly the background noise. The anisotropic design methodology also incorporates other results on filter design based on human vision which have recently been reported by the author and coworkers.

关键词： Finite impulse response filter Anisotropic filters image enhancement Humans Nonlinear filters Frequency response Additive noise image processing Anisotropic magnetoresistance Visual perception

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Improved pitch detection algorithm for noisy speech

Improved pitch detection algorithm for noisy speech

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International Conference on Acoustics, Speech, and Signal processing (ICASSP)

作者： Sanguoon Chung V. Algazi Signal and Image Processing Laboratory Department of Electrical and Computer Engineering University of California Davis CA USA

We propose a new, robust pitch detection algorithm for speech degraded by additive noise. Our algorithm exploits the high correlation between adjacent pitch periods that does not exist for the segment as a whole and performs well in the vicinity of voiced/unvoiced regions where the local SNR is low. The algorithm works as follows. We first determine an estimate of the pitch period near the short time peak energy where the local SNR is highest. We then adaptively estimate the local pitch period from the peak towards the transition region by using pitch synchronous cross-correlation with an updated waveform. The performance of this new algorithm is compared to the SIFT and CEPSTRUM algorithms.

关键词： Detection algorithms Speech enhancement Cepstrum Acoustic noise Working environment noise Detectors Cepstral analysis Algorithm design and analysis Time measurement Speech synthesis

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LEARNING CHARACTERISTICS OF STOCHASTIC-GRADIENT-DESCENT ALGORITHMS - A GENERAL STUDY, ANALYSIS, AND CRITIQUE

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SIGNAL processing 1984年第2期6卷 113-133页

作者： GARDNER, WA Signal and Image Processing Laboratory Department of Electrical and Computer Engineering University of California Davis 95616 USA

A comprehensive analysis of the mean-square learning characteristics of stochastic-descent algorithms is presented. The approach is based on the commonly exploited simplifying assumption of stationary independent training vectors. Characteristics analyzed include stability, steady-state misadjustment, initial rate of convergence, optimum step size, and steady-state autocovariance and spectral characteristics of the weight-vector. Effects on these characteristics due to degree of randomness of stochastic gradient, particular data distribution, and data corruption are isolated and analyzed. An objective of the work is to keep the number of simplifying assumptions and approximations to a minimum. Comparison of results with previous more approximate analyses are made. Lernkurven von stochastischen Gradienten Algorithmen werden untersucht. Die vereinfachende Annahme von stationären, unabhängigen Trainingsvektoren wird benutzt. Charakteristiken die untersucht werden beinhalten Stabilität, ‘steady state’ Fehlanpassung, Start Konvergenz, optimaler Schritt sowie ‘steady state’ Autokovarianz und spektrale Charakteristik des Gewichtsvektors. Die Effekten auf diese Charakteristiken von dem Zufälligkeitsgrad des stichastischen Gradienten, besonderer Daten Verteilung und Daten Verderbung werden isoliert und analysiert. Ein Zielpunkt dieser Arbeit ist es die Anzahl vereinfachenden Annahmen und Approximationen auf ein minimum zu beschränken. Vergleiche mit Resultaten die von approximativeren Analysen stammen werden gezogen. Une analyse d'ensemble des caractéristiques de convergence de l'erreur quadratique moyenne dans les algorithmes utilisant la décroissance du gradient stochastique est presentée. Cette approche est basée sur l'hypothése simplificatrice classique de stationnarité et indépendance des vecteurs de test. Les caractéristiques analysées comprennent la stabilité, l'écart d'état stable, la vitesse initiale de convergence, le pas optimum d'incrémentation, et l'autocovarian

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