Now showing items 1-50 of 50

  • An Adaptive Optimal-Kernel Time-Frequency Representation 

    Jones, Douglas L.; Baraniuk, Richard G. (1995-10-01)
    Time-frequency representations with fixed windows or kernels figure prominently in many applications, but perform well only for limited classes of signals. Representations with signal- dependent kernels can overcome this ...
  • Adaptive Wavelet Transforms via Lifting 

    Claypoole, Roger L.; Baraniuk, Richard G.; Nowak, Robert David (1999-05-01)
    This paper develops new algorithms for adapted multiscale analysis and signal adaptive wavelet transforms. We construct our adaptive transforms with the <i>lifting scheme</i>, which decomposes the wavelet transform into ...
  • Adaptive Weighted Highpass Filters Using Multiscale Analysis 

    Nowak, Robert David; Baraniuk, Richard G. (1998-07-01)
    In this paper, we propose a general framework for studying a class of weighted highpass filters. Our framework, based on a multiscale signal decomposition, allows us to study a wide class of filters and to assess the ...
  • Conditional and Relative Multifractal Spectra 

    Riedi, Rudolf H.; Scheuring, Istvan (1997-03-01)
    In the study of the involved geometry of singular distributions the use of fractal and multifractal analysis has shown results of outstanding significance. So far, the investigation has focused on structures produced by ...
  • Detecting Periodic Behavior in Nonstationary Signals 

    Venkatachalam, Vidya; Aravena, Jorge.L. (1998-10-20)
    This paper presents results on the multiresolution analysis of nonstationary signals with the objective of detecting underlying periodic phenomena. Wavelet packet analysis with coefficient thresholding is the basis for the ...
  • Detection of Target Speakers in Audio Databases 

    Magrin-Chagnolleau, Ivan; Rosenberg, Aaron; Parthasarathy, S. (1999-01-15)
    The problem of speaker detection in audio databases is addressed in this paper. Gaussian mixture modeling is used to build target speaker and background models. A detection algorithm based on a likelihood ratio calculation ...
  • Effect of Utterance Duration and Phonetic Content on Speaker Identification Usind Second Order Statistical Methods 

    Magrin-Chagnolleau, Ivan; Bonastre, Jean-Francois; Bimbot, Frederic (1995-01-01)
    Second-order statistical methods show very good results for automatic speaker identification in controlled recording conditions. These approaches are generally used on the entire speech material available. In this paper, ...
  • Efficient Methods for Identification of Volterra Filters 

    Nowak, Robert David; Van Veen, Barry D. (1996-02-01)
    A major drawback of the truncated Volterra series or "Volterra filter" for system identification is the large number of parameters required by the standard filter structure. The corresponding estimation problem requires ...
  • Empirical Mode Decomposition Based Frequency Attributes 

    Magrin-Chagnolleau, Ivan; Baraniuk, Richard G. (1999-11-01)
    This paper describes a new technique, called <i>Empirical Mode Decomposition</i> (EMD), which allows the decomposition of one-dimensional signals into intrinsic oscillatory modes. Each component, called <i>Intrinsic Mode ...
  • Equivalence of Generalized Joint Signal Representations of Arbitrary Variables 

    Sayeed, Akbar M.; Jones, Douglas L. (1996-12-20)
    Joint signal representations (JSRs) of arbitrary variables generalize time-frequency representations (TFRs) to a much broader class of nonstationary signal characteristics. Two main distributional approaches to JSRs of ...
  • Exceptions to the Multifractal Formalism for Discontinuous Measures 

    Riedi, Rudolf H.; Mandelbrot, Benoit (1998-01-15)
    In an earlier paper the authors introduced the <i>inverse measure</i> <i>µ</i><sup>â  </sup>(<i>dt</i>) of a given measure <i>µ</i>(<i>dt</i>) on [0,1] and presented the 'inversion formula' <i>f</i><sup>â  </sup>(<i>a</i>) ...
  • Fast, Exact Synthesis of Gaussian and nonGaussian Long-Range-Dependent Processes 

    Crouse, Matthew; Baraniuk, Richard G. (1999-01-15)
    1/<i>f</i> noise and statistically self-similar processes such as fractional Brownian motion (fBm) are vital for modeling numerous real-world phenomena, from network traffic to DNA to the stock market. Although several ...
  • A Further Investigation on AR-Vector Models for Text Independent Speaker Identification 

    Magrin-Chagnolleau, Ivan; Bimbot, Frederic (1996-01-01)
    In this paper, we investigate on the role of dynamic information on the performances of AR-vector models for speaker recognition. To this purpose, we design an experimental protocol that destroys the time structure of ...
  • Hybrid Linear / Bilinear Time-Scale Analysis 

    Pasquier, Martin; Goncalves, Paulo; Baraniuk, Richard G. (1999-01-01)
    We introduce a new method for the time-scale analysis of non-stationary signals. Our work leverages the success of the "time-frequency distribution series / cross-term deleted representations" into the time-scale domain ...
  • Image enhancement by nonlinear wavelet processing 

    Odegard, Jan E. (1994-10-20)
    In this paper we describe how the theory of wavelet thresholding introduced by Donoho and Johnstone can successfully be applied to two distinct problems in image processing where traditional linear filtering techniques are ...
  • An Improved Multifractal Formalism and Self Affine Measures 

    Riedi, Rudolf H. (1993-01-20)
    This document is a six page summary of my Ph.D. thesis in which multifractal formalism based on counting on coarse levels (as opposed to a dimensional approach) is developed. This formalism is then applied to self-affine ...
  • An Improved Multifractal Formalism and Self Similar Measures 

    Riedi, Rudolf H. (1995-01-01)
    To characterize the geometry of a measure, its so-called generalized dimensions D(<i>q</i>) have been introduced recently. The mathematically precise definition given by Falconer turns out to be unsatisfactory for reasons ...
  • Improved Time-Frequency Filtering of Signal-Averaged Electrocardiograms 

    Sayeed, Akbar M.; Jones, Douglas L. (1995-01-15)
    A recently proposed time-frequency filtering technique has shown promising results for the enhancement of signal-averaged electrocardiograms. This method weights the short-time Fourier transform (STFT) of the ensemble-averaged ...
  • Inverse Measures, the Inversion formula, and Discontinuous Multifractals 

    Mandelbrot, Benoit; Riedi, Rudolf H. (1997-01-20)
    The present paper is part I of a series of three closely related papers in which the inverse measure m' of a given measure m on [0,1] is introduced. In the first case discussed in detail, both these measures are multifractal ...
  • Inversion Formula for Continuous Multifractals 

    Riedi, Rudolf H.; Mandelbrot, Benoit (1997-01-20)
    In a previous paper the authors introduced the inverse measure <i>µ</i><sup>â  </sup> of a probability measure <i>µ</i> on [0,1]. It was argued that the respective multifractal spectra are linked by the 'inversion formula' ...
  • Joint Distributions of Arbitrary Variables Made Easy 

    Baraniuk, Richard G. (1998-10-01)
    In this paper, we propose a simple framework for studying certain distributions of variables beyond time-frequency and time-scale. When applicable, our results turn the theory of joint distributions of arbitrary variables ...
  • Low Rank Estimation of Higher Order Statistics 

    Nowak, Robert David; Van Veen, Barry D. (1995-12-01)
    Low rank estimators for higher order statistics are considered in this paper. Rank reduction methods offer a general principle for trading estimator bias for reduced estimator variance. The bias-variance tradeoff is analyzed ...
  • Multifractal Formalism for Infinite Multinomial Measures 

    Riedi, Rudolf H.; Mandelbrot, Benoit (1995-01-20)
    There are strong reasons to believe that the multifractal spectrum of DLA shows anomalies which have been termed left sided. In order to show that this is compatible with strictly multiplicative structures Mandelbrot et ...
  • Multifractal Properties of TCP Traffic: a Numerical Study 

    Riedi, Rudolf H.; Vehel, Jacques (1997-10-20)
    We analyze two traces of TCP--traffic recorded at the gateway of a LAN corre­ sponding to two hours at Berkeley and to eight hours at CNET labs respectively. We are mainly interested in a multifractal approach, which we ...
  • Noise Reduction Using an Undecimated Discrete Wavelet Transform 

    Lang, Markus; Guo, Haitao; Odegard, Jan E.; Burrus, C. Sidney; Wells, R.O. (1995-01-15)
    A new nonlinear noise reduction method is presented that uses the discrete wavelet transform. Similar to Donoho and Johnstone, we employ thresholding in the wavelet transform domain but, following a suggestion by Coifman, ...
  • Nonlinear Wavelet Processing for Enhancement of Images 

    Odegard, Jan E.; Lang, Markus; Guo, Haitao; Gopinath, Ramesh A.; Burrus, C. Sidney (1994-05-20)
    In this note we apply some recent results on nonlinear wavelet analysis to image processing. In particular we illustrate how the (soft) thresholding algorithm due to Donoho and Johnstone can successfully be used to remove ...
  • Nonstationary Signal Enhancement Using The Wavelet Transform 

    Venkatachalam, Vidya; Aravena, Jorge.L. (1996-03-20)
    Conventional signal processing typically involves frequency selective techniques which are highly inadequate for nonstationary signals. In this paper, we present an approach to perform time-frequency selective processing ...
  • Numerical Estimates of Generalized Dimensions D_q for Negative q 

    Riedi, Rudolf H. (1996-01-01)
    Usual fixed-size box-counting algorithms are inefficient for computing generalized fractal dimensions D(<i>q</i>) in the range of <i>q</i><0. In this Letter we describe a new numerical algorithm specifically devised to ...
  • On the Equivalence of the Operator and Kernel Methods for Joint Distributions of Arbitrary Variables 

    Sayeed, Akbar M. (1997-04-20)
    Generalizing the concept of time-frequency representations, Cohen has recently proposed a general method, based on operator correspondence rules, for generating joint distributions of arbitrary variables. As an alternative ...
  • Opitmal Phase Kernels for Time-Frequency Analysis 

    Wisur-Olsen, Fridtjof; Baraniuk, Richard G. (1996-05-01)
    We consider the design of kernels for time-frequency distributions through the phase, rather than amplitude, response. While phase kernels do not attenuate troublesome cross-components, they can translate them in the ...
  • An Overview of the AT&T Spoken Document Retrieval System 

    Choi, John; Hindle, Don; Hirschberg, Julia; Magrin-Chagnolleau, Ivan; Nakatani, Christine; Pereira, Fernando; Singhal, Amit; Whittaker, Steve (1998-01-15)
    We present an overview of a spoken document retrieval system developed at AT&T Labs-Research for the HUB4 Broadcast News corpus. This overview includes a description of the intonational phrase boundary detection, ...
  • Pseudo Affine Wigner Distributions 

    Goncalves, Paulo; Baraniuk, Richard G. (1996-05-01)
    In this paper, we introduce a new set of tools for time-varying spectral analysis: the pseudo affine Wigner distributions. Based on the affine Wigner distributions of J. and P. Bertrand, these new time-scale distributions ...
  • Pseudo Affine Wigner Distributions: Definition and Kernel Formulation 

    Goncalves, Paulo; Baraniuk, Richard G. (1998-06-01)
    In this paper, we introduce a new set of tools for time-varying spectral analysis: the pseudo affine Wigner distributions. Based on the affine Wigner distributions of J. and P. Bertrand, these new time-scale distributions ...
  • A Pseudo-Bertrand Distribution for Time-Scale Analysis 

    Goncalves, Paulo; Baraniuk, Richard G. (1996-03-01)
    Using the pseudo-Wigner time-frequency distribution as a guide, we derive two new time-scale representations, the pseudo-Bertrand and the smoothed pseudo-Bertrand distributions. Unlike the Bertrand distribution, these ...
  • Recent advances in Imaging and Spectroscopy with T-rays 

    Mittleman, Daniel M.; Neelamani, Ramesh; Gupta, Maya; Baraniuk, Richard G.; Nuss, Martin C. (1998-12-01)
    Recent work in terahertz "T-Ray" imaging is reported. With the ongoing development of commercially viable THz-TDS imaging system, opitmail signal processing strategies for the THz waveforms must be developed. Algorithms ...
  • SCAN - Speech Content Based Audio Navigator: A Systems Overview 

    Choi, John; Hindle, Don; Hirschberg, Julia; Magrin-Chagnolleau, Ivan; Nakatani, Christine; Pereira, Fernando; Singhal, Amit; Whittaker, Steve (1998-01-15)
    SCAN (Speech Content based Audio Navigator) is a spoken document retrieval system integrating speaker-independent, large-vocabulary speech recognition with information-retrieval to support query-based retrieval of information ...
  • Second-Order Statistical Measures for Text-Independent Speaker Identification 

    Bimbot, Frederic; Magrin-Chagnolleau, Ivan (1995-08-20)
    This article presents an overview of several measures for speaker recognition. These measures relate to second-order statistical tests, and can be expressed under a common formalism. Alternate formulations of these measures ...
  • A Simple Scheme for Adapting Time-Frequency Representations 

    Jones, Douglas L.; Baraniuk, Richard G. (1994-12-01)
    Signal-dependent time-frequency representations, by adapting their functional form to fit the signal being analyzed, offer many performance advantages over conventional representations. In this paper, we propose a simple, ...
  • A Simple Statistical Analysis of Wavelet-based Multifractal Spectrum Estimation 

    Goncalves, Paulo; Riedi, Rudolf H.; Baraniuk, Richard G. (1998-11-01)
    The multifractal spectrum characterizes the scaling and singularity structures of signals and proves useful in numerous applications, from network traffic analysis to turbulence. Of great concern is the estimation of the ...
  • Speaker Detection in Broadcast Speech Databases 

    Rosenberg, Aaron; Magrin-Chagnolleau, Ivan; Parthasarathy, S. (1998-01-15)
    Experiments have been carried out to assess the feasibility of detecting target speaker segments in multi-speaker broadcast databases. The experiemental database consists of NBC Nightly News broadcasts. The target speaker ...
  • Tensor Product Basis Approximations for Volterra Filters 

    Nowak, Robert David; Van Veen, Barry D. (1996-02-01)
    This paper studies approximations for a class of nonlinear filters known as Volterra filters. Although the Volterra filter provides a relatively simple and general representation for nonlinear filtering, often it is highly ...
  • Time Frequency Principal Components: Application to Speaker Identification 

    Magrin-Chagnolleau, Ivan; Durou, Geoffrey (1999-01-01)
    In this paper, we propose a formalism, called vector filtering of spectral trajectories, which allows to integrate under a common formalism a lot of speech parameterization approaches. We then propose a new filtering in ...
  • Toward an Improved Understanding of Network Traffic Dynamics 

    Riedi, Rudolf H.; Willinger, Walter (1999-06-20)
    Since the discovery of long range dependence in Ethernet LAN traces there has been significant progress in developing appropriate mathematical and statistical techniques that provide a physical-based, networking-related ...
  • Wavelet Analysis of Fractional Brownian Motion in Multifractal Time 

    Goncalves, Paulo; Riedi, Rudolf H. (1999-09-20)
    We study <i>fractional Brownian motions in multifractal time</i>, a model for multifractal processes proposed recently in the context of economics. Our interest focuses on the statistical properties of the wavelet decomposition ...
  • Wavelet Based SAR Speckle Reduction and Image Compression 

    Odegard, Jan E.; Guo, Haitao; Lang, Markus; Burrus, C. Sidney; Wells, R.O.; Novak, L.M.; Hiett, M. (1995-04-01)
    This paper evaluates the performance of the recently published wavelet based algorithm for speckle reduction of SAR images. The original algorithm, based on the theory of wavelet thresholding due to Donoho and Johnstone, ...
  • Wavelet Based Speckle Reduction with Applications to SAR based ATD/R 

    Guo, Haitao; Odegard, Jan E.; Lang, Markus; Gopinath, Ramesh A.; Selesnick, Ivan W.; Burrus, C. Sidney (1994-11-20)
    This paper introduces a novel speckle reduction method based on thresholding the wavelet coefficients of the logarithmically transformed image. The method is computational efficient and can sinificantly reduce the speckle ...
  • Wavelet-based deconvolution for ill-conditioned systems 

    Neelamani, Ramesh; Choi, Hyeokho; Baraniuk, Richard G. (2000-02-01)
    We propose a hybrid approach to wavelet-based deconvolution that comprises Fourier-domain system inversion followed by wavelet-domain noise suppression. In contrast to other wavelet-based deconvolution approaches, the ...
  • Wavelet-Based Post-Processing of Low Bit Rate Transform Coded Images 

    Gopinath, Ramesh A.; Lang, Markus; Guo, Haitao; Odegard, Jan E. (1994-11-01)
    In this paper we propose a novel method based on wavelet thresholding for enhancement of decompressed transform coded images. Transform coding at low bit rates typically introduces artifacts associated witht he basis ...
  • Wavelet-Based Transformations for Nonlinear Signal Processing 

    Nowak, Robert David; Baraniuk, Richard G. (1999-07-01)
    Nonlinearities are often encountered in the analysis and processing of real-world signals. In this paper, we introduce two new structures for nonlinear signal processing. The new structures simplify the analysis, design, ...
  • Wavelet-Domain Filtering for Photon Imaging Systems 

    Nowak, Robert David; Baraniuk, Richard G. (1999-05-01)
    Many imaging systems rely on photon detection as the basis of image formation. One of the major sources of error in these systems is Poisson noise due to the quantum nature of the photon detection process. Unlike additive ...