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Signal Processing Letters, IEEE

Issue 5 • Date May 2004

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Displaying Results 1 - 21 of 21
  • Table of contents

    Page(s): c1 - c4
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  • IEEE Signal Processing Letters publication information

    Page(s): c2
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  • Variation on variation on Euclid's algorithm

    Page(s): 457 - 458
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (77 KB) |  | HTML iconHTML  

    In a paper entitled "Variation on Euclid's Algorithm for Plynomials", Calvez et al. has shown that the extended Euclid's algorithm can be partially obtained by the nonextended one; in fact, it can obtain only two of the three unknowns of the Bezout's theorem. This letter goes further and shows that all polynomials given by the extended Euclid's algorithm and all the intermediate values can be obtained directly by the nonextended Euclid's algorithm. Consequently, only remainder computations are used. Avoiding multiplications and divisions of polynomials decreases the computational complexity. This variation of Calvez et al. justifies the title of the present letter. View full abstract»

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  • Split vector-radix-2/8 2-D fast Fourier transform

    Page(s): 459 - 462
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (464 KB) |  | HTML iconHTML  

    This letter presents an efficient split vector-radix-2/8 fast Fourier transform (FFT) algorithm. The split vector-radix-2/8 FFT algorithm saves 14% real multiplications and has much lower arithmetic complexity than the split vector-radix-2/4 FFT algorithm. Moreover, this algorithm reduces 25% data loads and stores compared with the split vector-radix-2/4 FFT algorithm. View full abstract»

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  • New distributed arithmetic algorithm for low-power FIR filter implementation

    Page(s): 463 - 466
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB) |  | HTML iconHTML  

    This letter proposes a new distributed arithmetic (DA) algorithm for low-power finite-impulse response (FIR) filter implementation. The characteristic of the proposed algorithm is that the FIR filters using the proposed algorithm do not need to employ two's complement representation in lookup tables as well as multiply-and-accumulation blocks. Thus, the proposed algorithm can minimize the dynamic power consumption of the FIR filters. The experimental results show that the lowpass FIR filter using the proposed algorithm achieves 29% and 26% power consumption reduction compared to that using the conventional algorithm for zero-mean random inputs and speech inputs, respectively. View full abstract»

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  • On passband criterion for eigenfilter design

    Page(s): 467 - 469
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (144 KB) |  | HTML iconHTML  

    In this letter, we propose a new passband criterion for eigenfilters. Instead of choosing the response at a particular frequency in the passband as the desired response, the new criterion chooses the average passband gain as the desired response. The new criterion does not increase the design cost. Simulations show that the proposed criterion leads to better filters both in least square sense and in minimax sense. View full abstract»

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  • Identifiability issues in noisy ICA

    Page(s): 470 - 473
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (120 KB) |  | HTML iconHTML  

    We consider the identifiability of the statistical model for noisy independent component analysis showing that while the mixing process is identifiable, the noise covariance is only partially so. This raises questions as to the performance of certain maximum-likelihood algorithms for blind source separation in the presence of noise. View full abstract»

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  • Competitive splitting for codebook initialization

    Page(s): 474 - 477
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (192 KB) |  | HTML iconHTML  

    Codebook initialization usually has a significant effect on the performance of vector quantization algorithms. This letter presents a new scheme of codebook initialization in which the competitive learning and code vector splitting are incorporated together to produce a good initial codebook. Based mainly on the geometrical measurements of the learning tracks of the code vectors, the competitive splitting mechanism shows an ability to appropriately allocate code vectors according to the spatial distribution of the input data and, therefore, tends to give a better initial codebook. Comparisons with other initialization techniques demonstrate the effectiveness of the new scheme. View full abstract»

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  • Kernel-based nonlinear beamforming construction using orthogonal forward selection with the fisher ratio class separability measure

    Page(s): 478 - 481
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB) |  | HTML iconHTML  

    This letter shows that the wireless communication system capacity is greatly enhanced by employing nonlinear beamforming and that the optimal Bayesian beamformer outperforms the standard linear beamformer significantly in terms of a reduced bit error rate, at a cost of increased complexity. A block-data adaptive implementation of the Bayesian beamformer is realized based on an orthogonal forward selection procedure with the Fisher ratio for class separability measure. View full abstract»

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  • An efficient fixed-point implementation of residual resampling scheme for high-speed particle filters

    Page(s): 482 - 485
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (192 KB)  

    A novel low-complexity residual resampling scheme for particle filters is presented. The proposed scheme uses a simple but effective "particle-tagging" method to compensate for a possible error that can be caused by finite-precision quantization in the resampling step of particle filtering. The scheme guarantees that the number of particles after resampling is always equal to the number of particles before resampling. The resulting scheme is suitable for high-speed physical realization when the number of particles is a power of two. View full abstract»

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  • Sparse spike train deconvolution using the hunt filter and a thresholding method

    Page(s): 486 - 489
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB) |  | HTML iconHTML  

    A new deconvolution method of sparse spike trains is presented. It is based on the coupling of the Hunt filter with a thresholding. We show that a good model for the probability density function of the Hunt filter output is a Gaussian mixture, from which we derive the threshold that minimizes the probability of errors. Based on an interpretation of the method as a maximum a posteriori (MAP) estimator, the hyperparameters are estimated using a joint MAP approach. Simulations show that this method performs well at a very low computation time. View full abstract»

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  • Cramer-Rao lower bound for estimating quadrupole resonance signals in non-Gaussian noise

    Page(s): 490 - 493
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB) |  | HTML iconHTML  

    Quadrupole resonance (QR) technology for the detection of explosives is of crucial importance in an increasing number of applications. For landmine detection, where the detection system cannot be shielded, QR has proven to be highly effective if the QR sensor is not exposed to radio-frequency interference (RFI). However, strong non-Gaussian RFI in the field is unavoidable. A statistical model of such non-Gaussian RFI noise is given in this letter. In addition, the asymptotic Cramer-Rao lower bound for estimating a deterministic QR signal in this non-Gaussian noise is presented. The performance of several convenient estimators is compared to this bound. View full abstract»

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  • Bifurcation analysis for third-order phase-locked loops

    Page(s): 494 - 496
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (88 KB) |  | HTML iconHTML  

    Second-order phase-locked loops (PLLs) are extensively used in applications related to recovering clock signals for synchronous demodulation in telecommunication networks. In situations where an improvement of the transient response of the local clocks is necessary, third-order PLLs are employed. Here, we use concepts taken from dynamical system theory for analytically determining the capture range of three nonlinear third-order PLLs subject to a ramp input. We show that saddle-node, saddle-saddle, and Hopf bifurcations can be produced by varying the values of the input signal velocity and of the PLL parameters, providing criteria for designing such PLLs. View full abstract»

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  • Time-varying multichirp rate modulation for multiple access systems

    Page(s): 497 - 500
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB) |  | HTML iconHTML  

    We propose a modulation scheme that is based on wideband time-varying chirp signals for use in frequency-hopped code division multiple-access systems. The scheme is designed such that each user is assigned unique modulating chirp signals that efficiently occupy the hop bandwidth for identification at the receiver. We explain how the chirp modulation reduces multiple-access interference, and we demonstrate with simulations our improved performance for various fading channels. The bandwidth efficiency of the chirp signaling is further exploited by assigning multiple chirp rates to each user. View full abstract»

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  • Source localization with isotropic arrays

    Page(s): 501 - 504
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (136 KB) |  | HTML iconHTML  

    We consider the effect of unknown signal propagation velocity on direction-of-arrival (DOA) estimation performance using an array of sensors. For general arrays, the DOA estimation variance, as measured by the Crame´r-Rao bound (CRB), degrades when the propagation velocity is unknown. In this letter, we show that for both two- and three-dimensional arrays, the CRB on the DOA angle is independent of whether or not the propagation velocity is known if and only if the sensor locations satisfy the isotropy conditions given in earlier work. The results hold for both narrowband and wideband signals. View full abstract»

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  • Improving DC coding models of JPEG arithmetic coder

    Page(s): 505 - 508
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (144 KB) |  | HTML iconHTML  

    While conducting experiments with JPEG binary arithmetic coding, we noticed that if a natural photographic image is rotated by 90° and then coded, the DC code size is reduced in general. This led us to investigate the discrete cosine transform and statistical models of JPEG arithmetic coder, and formulate two modifications to DC coefficient coding. We propose that the DC of a block should be predicted from the block just above. This modification reduces the DC code size further by about 9% on average. This change is more important for arithmetic coding than Huffman DC coding. We also propose a change in the binary decision coding order specified by the DC statistical model; it produces only a minor reduction in the code size. View full abstract»

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  • Nonefficiency of stochastic beamforming bearing estimates at high SNR and finite number of samples

    Page(s): 509 - 512
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    It is well known that the stochastic maximum-likelihood (SML) method yields Gaussian and efficient estimates when the number of independent identically distributed samples tends to infinity. This letter investigates the behavior of SML bearing estimation for a single source impinging on an antenna array when the SNR tends to infinity for a fixed number of samples. We prove that, rather surprisingly, the bearing estimates are not efficient and are asymptotically distributed according to a Student law. Simulation results confirm theoretical analysis. View full abstract»

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  • Direct position determination of narrowband radio frequency transmitters

    Page(s): 513 - 516
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB) |  | HTML iconHTML  

    The most common methods for location of communications or radar transmitters are based on measuring a specified parameter such as signal angle of arrival (AOA) or time of arrival (TOA). The measured parameters are then used to estimate the transmitter location. Since the AOA/TOA measurements are done at each base station separately, without using the constraint that all measurements must correspond to the same transmitter, they are suboptimal. We propose a technique that uses exactly the same data as the common methods, except that the estimation of location is based on exact maximum likelihood, and the location determination is direct. Although there are many stray parameters, including the attenuation coefficients and the signal waveform, the method requires only a two-dimensional search. Monte Carlo simulations indicate that the accuracy is equivalent to AOA, TOA, and their combination for high SNR, while for low SNR, the accuracy of the proposed method is superior. View full abstract»

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  • Cepstral domain segmental nonlinear feature transformations for robust speech recognition

    Page(s): 517 - 520
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (144 KB) |  | HTML iconHTML  

    This letter presents a new segmental nonlinear feature normalization algorithm to improve the robustness of speech recognition systems against variations of the acoustic environment. An experimental study of the best delay-performance tradeoff is conducted within the AURORA-2 framework, and a comparison with two commonly used normalization algorithms is presented. Computationally efficient algorithms based on order statistics are also presented. One of them is based on linear interpolation between sampling quantiles, and the other one is based on a point estimation of the probability distribution. The reduction in the computational cost does not degrade the performance significantly. View full abstract»

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  • An interference-suppressing RAKE receiver for the CDMA downlink

    Page(s): 521 - 524
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB) |  | HTML iconHTML  

    In this letter, we propose an interference-suppressing RAKE receiver for the code division multiple-access (CDMA) downlink. In the downlink, the received signal has a special structure that makes it possible for a RAKE receiver (which is a simple low-complexity linear receiver) with appropriately chosen weights to suppress interference efficiently. While there have been a few other interference-suppressing RAKE receivers proposed recently, our design is based on a different motivation, and we show that our approach significantly outperforms them especially when the number of active users in the cell is not large. View full abstract»

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  • IEEE Signal Processing Society Information

    Page(s): c3
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    Freely Available from IEEE

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