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Signal Processing Letters, IEEE

Issue 4 • Date April 2002

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Displaying Results 1 - 8 of 8
  • Optimal speech enhancement under signal presence uncertainty using log-spectral amplitude estimator

    Page(s): 113 - 116
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (222 KB)  

    We present an optimally modified log-spectral amplitude estimator, which minimizes the mean-square error of the log-spectra for speech signals under signal presence uncertainty. We propose an estimator for the a priori signal-to-noise ratio (SNR), and introduce an efficient estimator for the a priori speech absence probability. Speech presence probability is estimated for each frequency bin and each frame by a soft-decision approach, which exploits the strong correlation of speech presence in neighboring frequency bins of consecutive frames. Objective and subjective evaluation confirm superiority in noise suppression and quality of the enhanced speech. View full abstract»

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  • Robust image transmission using JPEG2000 and turbo-codes

    Page(s): 117 - 119
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (226 KB)  

    A method of combined source and channel coding is described that provides robustness to errors from a binary symmetric channel and uses the JPEG2000 (JP2) image compression standard. The source code rate and channel code rate are jointly optimized to produce a stream of fixed-size channel packets, such that the rate allocation complexity grows O(N/sup 2/) with the number of transmitted packets, N. Punctured turbo codes are used for channel coding, providing strong error protection. The rate allocation scheme presented obtains all necessary information from the JP2 encoder, and does not require image decompression. View full abstract»

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  • Axiomatic quantification of multidimensional image resolution

    Page(s): 120 - 122
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (209 KB)  

    We generalize the axiomatic quantification of one-dimensional (1-D) image resolution to the multidimensional case. The imaging system of interest is characterized by a nonnegative spatially invariant point spread function. The axioms extended from the 1-D counterparts include nonnegativity, continuity, translation invariance, rotation invariance, luminance invariance, homogeneous scaling, and serial combination properties. It is proved that the only resolution measure consistent with the axioms is proportional to the square root of the trace of the covariance matrix of the point spread function. View full abstract»

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  • Maximum likelihood estimation of OFDM carrier frequency offset

    Page(s): 123 - 126
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    We develop a maximum likelihood estimate for orthogonal frequency division multiplexing (OFDM) carrier frequency offset in the presence of virtual carriers. It is found that the resulting estimate has an identical form to that of a previously proposed blind OFDM carrier frequency offset estimate by Liu and Tureli (see IEEE Commun. Lett., vol.2, p.104-106, 1998). Insights are provided as to why these two algorithms are equivalent. View full abstract»

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  • An iterative algorithm for estimation of linear frequency modulated signal parameters

    Page(s): 127 - 129
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (199 KB)  

    We consider the problem of estimation of a nonstationary signal. The time-frequency characteristics and, more precisely, the instantaneous frequency (IF) of such a signal can be highlighted by the Wigner-Ville transform (WVT). Using the properties of the cross WVT, we develop an iterative algorithm taking into consideration the presence of wrong frequencies in the estimated IF sequence of the signal. Finally, computer simulations are performed in order to illustrate the behavior of this iterative scheme. View full abstract»

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  • Spectral estimation of nonstationary ARMA processes using the evolutionary cepstrum

    Page(s): 130 - 132
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (205 KB)  

    The spectral estimation problem of nonstationary autoregressive moving-average (ARMA) processes is considered and a new method is proposed for the estimation of the time-varying spectral content of such signals. The proposed method can be viewed as an extension of the estimator proposed earlier by the authors to the time-varying case. The AR part of the model is estimated by solving the time-varying modified Yule-Walker equations using an estimated time-varying autocorrelation function. An evolutionary cepstrum estimator is proposed, which is then used in a simple recursion to obtain the MA parameters of the model. View full abstract»

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  • On the completeness of the lattice factorization for linear-phase perfect reconstruction filter banks

    Page(s): 133 - 136
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (227 KB)  

    In this letter, we re-examine the completeness of the lattice factorization for M-channel linear-phase perfect reconstruction filter bank (LPPRFB) with filters of the same length L=KM as discussed by Tran et al. (see IEEE Trans. Signal Processing, vol.48, p.133-47, Jan. 2000). We point out that the assertion of completeness is incorrect. Examples are presented to show that the proposed lattice structure of Tran et al. is not complete when K>2. In addition, we verify that the lattice structure is complete only when K/spl les/2. View full abstract»

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  • Optimized orthogonal matching pursuit approach

    Page(s): 137 - 140
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (230 KB)  

    An adaptive procedure for signal representation is proposed. The representation is built up through functions (atoms) selected from a redundant family (dictionary). At each iteration, the algorithm gives rise to an approximation of a given signal, which is guaranteed (1) to be the orthogonal projection of a signal onto the subspace generated by the selected atoms and (2) to minimize the norm of the corresponding residual error. The approach is termed optimized orthogonal matching pursuit because it improves upon the earlier proposed matching pursuit and orthogonal matching pursuit approaches. View full abstract»

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Aims & Scope

The IEEE Signal Processing Letters is a monthly, archival publication designed to provide rapid dissemination of original, cutting-edge ideas and timely, significant contributions in signal, image, speech, language and audio processing.

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Meet Our Editors

Editor-in-Chief
Peter Willett
University of Connecticut
Storrs, CT 06269
peter.willett@uconn.edu