1997 IEEE International Conference on Acoustics, Speech, and Signal Processing

21-24 April 1997

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  • 1997 IEEE International Conference On Acoustics, Speech, And Signal Processing

    Publication Year: 1997, Page(s):iii - xv
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    Freely Available from IEEE
  • Robust impulse noise suppression using adaptive wavelet de-noising

    Publication Year: 1997, Page(s):3417 - 3420 vol.5
    Cited by:  Papers (6)  |  Patents (2)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (396 KB)

    It is widely acknowledged that the effect of impulsive noise is a major source of performance degradation within a wide range of communication systems. This is due to the fact that non-Gaussian interference is neglected within the system design philosophy for reasons of complexity and tractability. We directly address this problem using a novel 'de-noising' technique in which significant performan... View full abstract»

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  • Robust wavelet thresholding for noise suppression

    Publication Year: 1997, Page(s):3421 - 3424 vol.5
    Cited by:  Papers (5)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (365 KB)

    Approaches to wavelet-based denoising (or signal enhancement) have so far relied on the assumption of normally distributed perturbations. To relax this assumption, which is often violated in practice, we derive a robust wavelet thresholding technique based on the minimax description length principle. We first determine the least favorable distribution in the /spl epsi/-contaminated normal family a... View full abstract»

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  • Independence/decorrelation measures with applications to optimized orthonormal representations

    Publication Year: 1997, Page(s):3425 - 3428 vol.5
    Cited by:  Papers (4)  |  Patents (3)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (339 KB)

    Extended forms of contrast functions are introduced to provide statistical measures of independence for orthogonal mixtures. We also define semicontrasts based on second-order statistics which, in some cases, may be sufficient to separate the mixed sources. The corresponding criteria are then used to obtain an optimized representation of a stochastic process in an orthonormal basis of wavelet pack... View full abstract»

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  • Signal estimation using wavelet-Markov models

    Publication Year: 1997, Page(s):3429 - 3432 vol.5
    Cited by:  Papers (5)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (451 KB)

    Current wavelet-based statistical signal and image processing techniques such as shrinkage and filtering treat the wavelet coefficients as though they were statistically independent. This assumption is unrealistic; considering the statistical dependencies between wavelet coefficients can yield substantial performance improvements. We develop a new framework for wavelet-based signal processing that... View full abstract»

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  • Multiple-window wavelet transform and local scaling exponent estimation

    Publication Year: 1997, Page(s):3433 - 3436 vol.5
    Cited by:  Papers (3)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (395 KB)

    We propose here a multiple-window wavelet transform for the purpose of identifying non-stationary self-similar structures in random processes and estimating the time-varying scaling exponent H(t) that controls the local regularity and correlation of the process. More specifically, our final aim is to be able to track even rapidly varying trajectories (t, H(t)). The solution described here combines... View full abstract»

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  • Blind SDMA with a signal space geometry matched algorithm

    Publication Year: 1997, Page(s):3437 - 3440 vol.5
    Cited by:  Papers (2)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (402 KB)

    We address the problem of the blind reconstruction of binary sequences transmitted by P sources, sharing simultaneously the same frequency channel. This is the situation in space division multiple access (SDMA) systems, where an array receiver is used to discriminate the spatial signatures of the sources. We exploit the geometry induced by the finite nature of the sources alphabet in order to deri... View full abstract»

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  • Using fractional cyclic moments of CPFSK signals in blind adaptive beamforming

    Publication Year: 1997, Page(s):3441 - 3444 vol.5
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (439 KB)

    This paper explains how fractional cyclic moments of CPFSK signals can be used in adaptive beamforming. It is shown that CPFSK signals have non-zero fractional cyclic moments because they generate spectral lines when they are raised to the inverse of its modulation index, which is generally a fractional number. To exploit this property, an optimization criterion is proposed to compute the antenna ... View full abstract»

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  • Separation of zero/constant modulus signals

    Publication Year: 1997, Page(s):3445 - 3448 vol.5
    Cited by:  Papers (16)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (407 KB)

    Zero/constant modulus (ZCM) signals are complex signals for which every sample is either zero or has modulus 1. Such signals arise after imprecise carrier-to-baseband conversion of binary {0,1}-modulated signals, or with intermittent phase-modulated signals. We consider the separation of linear superpositions of such signals using analytic techniques. An application is the separation of multiple p... View full abstract»

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  • Estimating equations for source separation

    Publication Year: 1997, Page(s):3449 - 3452 vol.5
    Cited by:  Papers (6)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (413 KB)

    This paper proposes a unifying view of source separation via the concepts of 'estimating function' and 'estimating equation'. We exhibit the estimating functions corresponding to various known techniques like ICA, JADE, infomax, maximum likelihood, cumulant matching, etc... We also show how equivariant batch and adaptive algorithms stem from each particular estimating function and discuss their st... View full abstract»

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  • Improved contrast dedicated to blind separation in communications

    Publication Year: 1997, Page(s):3453 - 3456 vol.5
    Cited by:  Papers (36)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (365 KB)

    Contrast-based separation of sources have a number of advantages. Among others, they are optimal (in a precise sense) in the presence of noise of unknown statistics. Here a new contrast is proposed that allows not only to obtain the optimal solution analytically, but also yields better performances in terms of variance of the estimated mixing matrix. This contrast needs the source kurtosis to have... View full abstract»

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  • A new multichannel blind equalization criterium based on a generalized Rayleigh quotient

    Publication Year: 1997, Page(s):3457 - 3460 vol.5
    Cited by:  Papers (3)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (353 KB)

    Recent works have presented novel techniques that exploit cyclostationarity for channel identification (equalization) in data communication systems using only second order statistics. In particular, the feasibility of blind identification based on the 'forward shift' structure of the correlation matrices of the source has been shown. In this paper we propose an alternative algorithm based on this ... View full abstract»

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  • A test statistic for sequential identification of co-channel digital signals using a deflation approach

    Publication Year: 1997, Page(s):3461 - 3464 vol.5
    Cited by:  Papers (1)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (315 KB)

    When sequentially separating a linear combination of co-channel digital signals, it is necessary at each step to test the validity of the currently estimated signal prior to proceeding to extract the next one. We describe a procedure for use with sequential algorithms which uses a deflation-based approach combined with a simple test statistic. The deflation step removes the contributions of the cu... View full abstract»

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  • Second-order blind identifiability of certain classes of multipath channels using antenna arrays

    Publication Year: 1997, Page(s):3465 - 3468 vol.5
    Cited by:  Papers (2)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (374 KB)

    Recently, a number of classes of multipath channels which are not blindly identifiable from fractionally spaced samples and second-order cyclic spectra have been presented. In this paper, we consider the blind identification problem of these channels using multiple antennas and show that they will not in general give rise to any common roots among the sub-channels formed from the antennas, and hen... View full abstract»

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  • Blind source separation using time-frequency distributions: algorithm and asymptotic performance

    Publication Year: 1997, Page(s):3469 - 3472 vol.5
    Cited by:  Papers (12)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (374 KB)

    This paper addresses the problem of the blind source separation which consists of recovering a set of signals of which only instantaneous linear mixtures are observed. A blind source separation approach exploiting the difference in the time-frequency (t-f) signatures of the sources is considered. The approach is based on the diagonalization of a combined set of 'spatial time-frequency distribution... View full abstract»

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  • Blind signal extraction based on higher-order cyclostationarity properties

    Publication Year: 1997, Page(s):3473 - 3476 vol.5
    Cited by:  Papers (2)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (461 KB)

    The paper deals with signal extraction performed by processing data received by an array of sensors. The proposed method is blind, i.e., it does not require any a priori knowledge of directional information associated with the signals of interest (SOI's). Such information is obtained directly from the received data by exploiting the higher-order cyclostationarity (HOCS) properties exhibited by mos... View full abstract»

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  • A new least squares approach to blind beamforming

    Publication Year: 1997, Page(s):3477 - 3480 vol.5
    Cited by:  Papers (3)  |  Patents (20)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (297 KB)

    We present a new two-step approach to blind beamforming based on the least squares criterion. The first step consists of "whitening" the array received vector, i.e., transforming its response matrix to some unknown unitary matrix. The second step consists of estimating the unitary matrix from the fourth order cumulants by a least squares criterion. In contrast to the corresponding "joint diagonali... View full abstract»

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  • Linear constraints in pre-Doppler STAP processing

    Publication Year: 1997, Page(s):3481 - 3484 vol.5
    Cited by:  Papers (1)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (436 KB)

    This paper addresses the issue of employing space-time adaptive processing (STAP) prior to Doppler filtering in radar systems. When STAP beamformer processing is applied to spatial/temporal samples that include successive radar pulses, the adaptive weights can cause modulation (spreading) of the desired target Doppler. In this paper, a linearly constrained adaptive beamformer is proposed that ensu... View full abstract»

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  • Multipath direction finding with subspace smoothing

    Publication Year: 1997, Page(s):3485 - 3488 vol.5
    Cited by:  Papers (12)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (404 KB)

    Antenna arrays can be employed in mobile communications to increase channel capacity as well as communication quality via spatially selective reception/transmission at base stations. In most wireless communications systems, directions of arrival of multipath signals need to be found for spatial selective transmission. Unfortunately, due to the coherent nature of multipath signals, it is quite diff... View full abstract»

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  • Closed-form multi-dimensional multi-invariance ESPRIT

    Publication Year: 1997, Page(s):3489 - 3492 vol.5
    Cited by:  Papers (9)  |  Patents (1)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (400 KB)

    A closed-form multi-dimensional multi-invariance generalization of the ESPRIT algorithm is introduced to exploit the entire invariance structure underlying a (possibly) multiparametric data model, thereby greatly improving estimation performance. The multiple-invariance data structure that this proposed method can handle includes: (1) multiple occurrence of one size of invariance along one or mult... View full abstract»

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  • Structured covariance estimation for space-time adaptive processing

    Publication Year: 1997, Page(s):3493 - 3496 vol.5
    Cited by:  Papers (15)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (449 KB)

    Adaptive algorithms require a good estimate of the interference covariance matrix. In situations with limited sample support such an estimate is not available unless there is structure to be exploited. In applications such as radar space-time adaptive processing (STAP) the underlying covariance matrix is structured (e.g., block Toeplitz), and it is possible to exploit this structure to arrive at i... View full abstract»

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  • Tracking moving sources using subspace-based adaptive linear methods

    Publication Year: 1997, Page(s):3497 - 3500 vol.5
    Cited by:  Papers (1)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (435 KB)

    Several works reported in the literature show that the subspace-based linear methods are computationally much more interesting than the eigendecomposition-based techniques and only slightly less accurate from the statistical point of view. They therefore have a clear potential for real time applications. Here we retain the basic ideas behind this class of methods and formulate the subspace trackin... View full abstract»

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  • Direction-of-arrival and frequency estimation using Poisson-Gaussian modeling

    Publication Year: 1997, Page(s):3501 - 3504 vol.5
    Cited by:  Papers (4)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (449 KB)

    We address the problem of identification of sinusoidal components from observed data, which is fundamental for array signal processing and spectral line decomposition. Joint detection and estimation are proposed in a unified Bayesian framework, so that no preliminary estimate of the number of signals is required. All unknown quantities are estimated from a unique regularized "stochastic" likelihoo... View full abstract»

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  • An entropy based approach for direction-of-arrival estimation in Gaussian and non-Gaussian correlated noise

    Publication Year: 1997, Page(s):3505 - 3508 vol.5
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (360 KB)

    In this paper, we present an entropy based approach for DOA estimation in Gaussian and non-Gaussian environments. The DOA estimates are obtained by minimizing an entropy measure of the array data in the noise subspace. We show that the entropy approach leads to the MAP algorithm under the Gaussian assumption. Under the non-Gaussian assumption, we apply the varimax norm as an information measure. A... View full abstract»

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  • Comparative study of IQML and MODE for direction-of-arrival estimation

    Publication Year: 1997, Page(s):3509 - 3512 vol.5
    Cited by:  Papers (2)
    Request permission for reuse | Click to expandAbstract | PDF file iconPDF (349 KB)

    We present a comparative study of using the IQML (iterative quadratic maximum likelihood) algorithm and the MODE (method of direction estimation) algorithm for direction-of-arrival estimation with a uniform linear array. The consistent condition and the theoretical mean-squared error for the parameter estimates of IQML are presented. The computational complexities of both algorithms are also compa... View full abstract»

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