Now showing items 1-20 of 130

    • 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 limitation. However, while they often perform well, most existing schemes are block-oriented techniques unsuitable for on-line ...
    • Adaptive Wavelet Transforms via Lifting 

      Claypoole, Roger L.; Baraniuk, Richard G.; Nowak, Robert David (1998)
      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 prediction and update stages. We adapt the prediction stage to the signal structure and design the update stage to preserve the ...
    • 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 merits of each. We derive an automatic procedure to tune a filter to the local structure of the image under consideration. The entire ...
    • Automatic Generation of Prime Length FFT Programs 

      Selesnick, Ivan W.; Burrus, C. Sidney (1996-01-01)
      We describe a set of programs for circular convolution and prime length FFTs that are short, possess great structure, share many computational procedures, and cover a large variety of lengths. The programs make clear the structure of the algorithms and clearly enumerate independent computational branches that can be performed in parallel. Moreover, ...
    • Bayesian Tree-Structured Image Modeling using Wavelet-domain Hidden Markov Models 

      Romberg, Justin; Choi, Hyeokho; Baraniuk, Richard G. (2001-07-01)
      Wavelet-domain hidden Markov models have proven to be useful tools for statistical signal and image processing. The hidden Markov tree (HMT) model captures the key features of the joint probability density of the wavelet coefficients of real-world data. One potential drawback to the HMT framework is the need for computationally expensive iterative ...
    • Beyond Time Frequency Analysis: Energy Densities in One and Many Dimensions 

      Baraniuk, Richard G. (1998-09-01)
      Given a unitary operator A representing a physical quantity of interest, we employ concepts from group representation theory to define two natural signal energy densities for A. The first is invariant to A and proves useful when the effect of A is to be ignored; the second is covariant to A and measures the "A" content of signals. The ...
    • Broadcast Detection Structures with Applications to Sensor Networks 

      Lexa, Michael; Johnson, Don (2006-03-01)
      Data broadcasting is potentially an effective and efficient way to share information in wireless sensor networks. Broadcasts offer energy savings over multiple, directed transmissions, and they provide a vehicle to exploit the statistical dependencies often present in distributed data. In this paper, we examine two broadcast structures in the context ...
    • A Canonical Covariance Based Method for Generalized Joint Signal Representations 

      Jones, Douglas L.; Sayeed, Akbar M. (1996-04-20)
      Generalized joint signal representations extend the scope of joint time-frequency representations to a richer class of nonstationary signals. Cohen's marginal-based generalized approach is canonical from a distributional viewpoint, whereas, in some other applications, for example, in a signal detection framework, a covariance-based formulation is ...
    • Coherent Multiscale Image Processing using Quaternion Wavelets 

      Chan, Wai Lam; Choi, Hyeokho; Baraniuk, Richard G. (2006-10-01)
      The quaternion wavelet transform (QWT) is a new multiscale analysis tool for geometric image features. The QWT is a near shift-invariant tight frame representation whose coefficients sport a magnitude and three phases: two phases encode local image shifts while the third contains image texture information. The QWT is based on an alternative theory ...
    • Complex Wavelet Transforms with Allpass Filters 

      Fernandes, Felix; Selesnick, Ivan W.; van Spaendonck, Rutger; Burrus, C. Sidney (2003-08-20)
      Complex discrete wavelet transforms have significant advantages over real wavelet transforms for certain signal processing problems. Two approaches to the implementation of complex wavelet transforms have been proposed earlier. Both approaches require discrete-time allpass systems having approximately linear-phase and (fractional) delay. This paper ...
    • 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 one single mechanism which were analyzed with respect to the ordinary metric or volume. Most prominent examples include self-similar ...
    • The Connexions Project: Promoting Open Sharing of Knowledge for Education 

      Henry, Geneva; Baraniuk, Richard G.; Kelty, Christopher (2003-07-01)
      The Connexions project at Rice University has created an open repository of educational materials and tools to promote sharing and exploration of knowledge as a dynamic continuum of interrelated concepts. Available free of charge to anyone under open-content and open-source licenses, Connexions offers high-quality, custom-tailored electronic course ...
    • Constrained Least Square Design of FIR Filters Without Specified Transition Bands 

      Selesnick, Ivan W.; Lang, Markus; Burrus, C. Sidney (1996-01-15)
      We consider the design of digital filters and discuss the inclusion of explicitly specified transition bands in the frequency domain design of FIR filters. We put forth the notion that explicitly specified transition bands have been introduced in the filter design literature as an indirect and sometimes inadequate approach for dealing with discontinuities ...
    • Covariant Time Frequency Representations Through Unitary Equivalence 

      Baraniuk, Richard G. (1996-03-01)
      We propose a straightforward characterization of all quadratic time-frequency representations covariant to an important class of unitary signal transforms (namely, those having two continuous-valued parameters and an underlying group structure). Thanks to a fundamental theorem from the theory of Lie groups, we can describe these representations ...
    • Development of Digital Signal Processor controlled Quantum Cascade Laser based Trace Gas Sensor Technology 

      So, Stephen; Wysocki, Gerard; Frantz, Patrick; Tittel, Frank K. (2006-08-01)
      This work reports the design and integration of a custom digital signal processor (DSP) system into a pulsed quantum cascade laser (QCL) based trace gas sensor to improve its portability, robustness and operating performance. Specifically, this work describes the implementation of a custom prototype DSP data acquisition/system controller based on the ...
    • Diverging moments and parameter estimation 

      Goncalves, Paulo; Riedi, Rudolf H. (2004-01-15)
      Heavy tailed distributions enjoy increased popularity and become more readily applicable as the arsenal of analytical and numerical tools grows. They play key roles in modeling approaches in networking, finance, hydrology to name but a few. The tail parameter is of central importance as it governs both the existence of moments of positive order and ...
    • The Dual-Tree Complex Wavelet Transform 

      Selesnick, Ivan W.; Baraniuk, Richard G.; Kingsbury, Nicholas G. (2005-11-01)
      The paper discusses the theory behind the dual-tree transform, shows how complex wavelets with good properties can be designed, and illustrates a range of applications in signal and image processing. The authors use the complex number symbol C in CWT to avoid confusion with the often-used acronym CWT for the (different) continuous wavelet transform. ...
    • Efficient Approximation of Continuous Wavelet Transforms 

      Jones, Douglas L.; Baraniuk, Richard G. (1991-04-01)
      An efficient method, based on the chirp-z transform, for computing equally spaced time samples of a continuous wavelet transform at arbitrary scale samples is developed. Applications include efficient computation of samples of the continuous wavelet transform and the broadband ambiguity function for time-frequency and time-scale signal analysis, and ...
    • Efficient Methods for Identification of Volterra Filters 

      Nowak, Robert David; Van Veen, Barry D. (1994)
      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 the solution of a large system of simultaneous linear equations. Two methods for simplifying the estimation problem are discussed ...
    • Efficient VLSI architectures for multiuser channel estimation in wireless base-station receivers 

      Rajagopal, Sridhar; Bhashyam, Srikrishna; Cavallaro, Joseph R.; Aazhang, Behnaam (2002-06-20)
      This paper presents a reduced-complexity, fixed-point algorithm and efficient real-time VLSI architectures for multiuser channel estimation, one of the core baseband processing operations in wireless base-station receivers for CDMA. Future wireless base-station receivers will need to use sophisticated algorithms to support extremely high data rates ...