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Control, Communications and Signal Processing, 2004. First International Symposium on

Date 21-24 March 2004

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Displaying Results 1 - 25 of 248
  • Signal processing challenges for wireless communications

    Page(s): 881 - 892
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2198 KB) |  | HTML iconHTML  

    Wireless communications allow for the application of a number of signal processing techniques. However, in many instances the success of the application depends on the proper accounting for the interaction of the signal processing problem with other disciplines such as propagation and channel modeling, communication and information theory, and processor circuit architectures. We discuss the incidence of propagation studies and channel modeling on channel correlation and hence on channel estimation performance (orthogonality of pilots), the interaction between modulation technique and the ease of training based channel estimation, the interaction between transmission scheme (continuous or block-wise) and temporal fading modeling and handling, modulation and signal processing (linear preceding) for diversity exploitation, approximate normal equation solutions for various signal types (speech vs CDMA, sparse significant correlations vs. dense weak correlations), interaction between channel modeling and CDMA receiver circuit architecture, higher-level adaptivity in adaptive filtering (filter order, temporal variation scale) and robustness in receiver design with estimated parameters. View full abstract»

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  • Enhancement and GIF filtering for the improvement of the mammographique image

    Page(s): 247 - 250
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1583 KB) |  | HTML iconHTML  

    The cancer of the breast is the type of cancer that touches more of women in the world. Nowadays, one appraises that one out of ten women has a risk to be touched by this type of cancer. The best means to fight against this illness is through prevention by the precocious tracking slant. Through the intermediary of mammographic exams, these exams permit to discover the different lesions of the breast (microcalcification) and has a primordial role in the struggle against the cancer of the breast. It is in this setting that several works have started to come in to help radiologists at the time of their diagnoses. In this context, our work consists of two well-known complex problems, improvement by filtering and enhancement, whose feasibility remains to be proven again. We present in this article a technique of enhancement and GIF filtering in order to detect microcalcificationses while achieving a more effective algorithm. View full abstract»

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  • A comparative study of some simplified RLS-type algorithms

    Page(s): 705 - 708
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1567 KB) |  | HTML iconHTML  

    The recursive least squares (RLS) algorithm has established itself as the "ultimate" adaptive filtering algorithm in the sense that it is the adaptive filter exhibiting the best convergence behavior. Unfortunately, practical implementations of the algorithm are often associated with high computational complexity and/or poor numerical properties. Rather than focusing on full RLS algorithm implementations aiming directly at remedying these problems, we argue that the use of simplified or partial RLS algorithms may be a viable alternative to full RLS. In particular, we point out that two recently introduced algorithms, fast Euclidian direction search (FEDS) and recursive adaptive matching pursuit (RAMP) can indeed be interpreted as such partial RLS algorithms exhibiting a nice tradeoff between complexity and performance. We support our presentation by a comprehensive set of simulation results. View full abstract»

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  • A solution to reduce noise enhancement in pre-whitened LMS-type algorithms: the double direction adaptation

    Page(s): 717 - 720
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1495 KB) |  | HTML iconHTML  

    The LMS algorithm suffers from its slow rate of convergence, especially for high correlated input signal. The input pre-whitening based algorithms provide better convergence rate with the price of noise enhancement. To mitigate this noise enhancement, we present in this paper a technique, which consists on exciting simultaneously the adaptive filter at two directions: the input and the pre-whitened input directions. The proposed algorithm improves the rate of convergence without enhancing the noise. An analytical analysis of both convergence rate and steady state performances is presented. Simulation results are also presented to support the analysis and to compare the proposed algorithm with classical ones. View full abstract»

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  • Programmable current source dedicated to a cochlear implant

    Page(s): 251 - 254
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1505 KB) |  | HTML iconHTML  

    In this paper, a novel architecture of a programmable current-source based on miniaturized digital-to-analog converters (DAC) was proposed. Such new design would be dedicated to cochlear implant circuit. In this study, our main objective was to look for one model that could include, as close as possible, several criteria related to the implant functionality such as reliability, flexibility, energy efficiency and integration area. Hence, this 6-bit DAC architecture was conceived in order to be adequate for a programmable current-source. Our design was able to generate a 2mA maximum current through a 1KΩ load, which is around the typical nerve impedance. Simulation results showed good linearity, low power consumption and a low area occupation. Resulting circuit was simulated by PSPICE tool using the 0.35μm CMOS technology. View full abstract»

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  • Estimation of closely-spaced paths via particle filters for WCDMA positioning

    Page(s): 791 - 794
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1532 KB) |  | HTML iconHTML  

    Multipath delay estimation is an important and challenging issue for any mobile communication system. Severe transmission conditions in fast changing environment, such as strong interference, shadowing or closely spaced multipaths may affect the capability of estimating correctly the channel parameters. In mobile positioning, accurate estimates of line-of-sight delay with a resolution less than one chip are needed to locate correctly the mobile receiver. Another challenging issue in multipath delay estimation in CDMA networks is the nonlinear dependency of the channel with respect to the multipath delays. In this paper, we introduce a particle-based sequential Monte Carlo filter for joint estimation of channel coefficients and delays in multiuser closely spaced paths WCDMA environment. The simulation results show that the proposed algorithm is stable, fast converging, and outperforms the classic extended Kalman filter-based approach. View full abstract»

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  • Phase approximation in linear and logarithmic frequency domain

    Page(s): 709 - 712
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1480 KB) |  | HTML iconHTML  

    The goal of this paper is to give a comparison between two methods for phase approximations: non-compact gain technique for linear frequency domain and the approach based on logarithmic sampling of gain for logarithmic frequency domain. The first procedure cannot be employed when the gain characteristic has slopes different from zero at zero and at high frequency. The Bode transfer functions do not satisfy the last requirement. To overpass this inconvenient, we have proposed the modified Bode transfer functions. Computer simulations are also presented. View full abstract»

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  • Genetic networks inferred from time series of gene expression data

    Page(s): 755 - 758
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1536 KB) |  | HTML iconHTML  

    The paper considers the problem of building genetic networks from time series of gene expression data. The class of models of interest is that of systems of differential equations specifying gene-gene interactions and the goal is to infer the network structure from experimental gene expression data. As a mean to regularize the inverse problem, we assume the biologically plausible constraint which imposes limits on the number of genes interacting with any given gene. The existing algorithms for inferring gene network structure heavily rely on the transformation of the system of differential equations into an approximative discretized system. In contrast, our proposed algorithms infer the structure of the gene networks by operating with the exact solutions of the differential equations. For the case of time series of non-uniformly sampled gene expressions, we first fit an optimal sum of exponentials model to each gene, where the best fit is defined by the minimum description length (MDL) principle, the optimal model being subsequently used for interpolating the data at a finer and equidistant grid in time. As a simulating environment we take simple genetic networks, assumed to be the ground truth, where the dynamical interactions between genes are postulated to be linear differential equations. We show that we can recover the sparse structure of the original model using the data generated by the system for a wide range of model parameters (i.e. strengths of the gene-gene interactions). View full abstract»

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  • Algorithmic methods for bottom-up generation of system-level RF macromodels

    Page(s): 57 - 62
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1877 KB) |  | HTML iconHTML  

    During the design of electronic circuits and systems, particularly those for RF communications, the need to abstract a subsystem from a greater level of detail to one at a lower level of detail arises frequently. One important application is to generate simple, yet accurate, system-level macromodels that capture circuit-level non-idealities such as distortion. In recent years, computational ("algorithmic") techniques have been developed that are capable of automating this abstraction process for broad classes of differential-equation-based systems (including non-linear ones). In this paper, we review the main ideas and techniques behind such algorithmic macromodelling methods. View full abstract»

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  • Model order estimation of InSAR signals corrupted by multiplicative noise using the Capon method

    Page(s): 873 - 876
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1479 KB) |  | HTML iconHTML  

    In this paper, we compare the performance of the Capon approach and the efficient detection criteria when applied to model order estimation of InSAR signals corrupted by multiplicative noise and additive white noise. This study is done in terms of the normalized baseline, the number of looks, the signal to noise ratio and the interferometric phase separation. Through the numerical simulations, we show, except the case of very closed sources, that the Capon method has the best performances. View full abstract»

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  • Transcutaneous electrical nerve stimulation for pain relief

    Page(s): 255 - 258
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1473 KB) |  | HTML iconHTML  

    In this article, we propose to study and to conceive a programmable signal generator allowing inhibition of certain types of pain. This system would be provided with an electrode which could be applied in the periphery level of the patient's spinal cord in order to excite the nervous zone responsible for pain transmission. The conceived system would be commanded with variable voltages and piloted by a dedicated microcontroller. This would allow us to have different possibilities in conceiving various shapes of stimulating waves. The purpose is to offer flexibility during clinical adjustments especially when programming the various parameters of electrical stimuli. A PC connection was also provided in order to visualize and to adjust stimulating wave parameters. Our system could be then considered as an original one since it is enhanced by flexibility and maneuverability during clinical trials. View full abstract»

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  • Design of DCT_2D toward FPGA

    Page(s): 713 - 716
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1599 KB) |  | HTML iconHTML  

    Long term objective is to conceive a system on chip of the JPEG coding chain. This article presents the VHDL specification, simulation and also synthesis results, of the two-dimensional discrete cosine transform DCT_2D, which constitutes the first block of the JPEG chain. For that, we kept LOEFLER's algorithm which is the best for the DCT implementation, according to a comparison with other architectures. And we targeted the FPGAs as integration technology. Besides, seeing that the DCT is separable as transformation, the two-dimensional discrete cosine transform (DCT_2D) can be formed by two one-dimensional discrete cosine transform (DCT_1D). View full abstract»

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  • Adaptive source and channel re-encoding to maximize tandem link performance

    Page(s): 583 - 586
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1587 KB) |  | HTML iconHTML  

    We investigate the issues in voice communications over tandem heterogeneous network connections, which require multiple source decoding/encoding operations. While it is known from speech coding research that tandem connections of different speech coders can extract a substantial performance penalty, it is shown that the use of error concealment and source re-encoding can improve system performance in the presence of channel impairments such as bit errors and packet losses. A new protocol is proposed for wireless LANs that reduces retransmissions and discarded packets, and hence reduces system delay and facilitates packet loss concealment. View full abstract»

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  • Analysis of phase noise effects in multi-user OFDM

    Page(s): 63 - 66
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1490 KB) |  | HTML iconHTML  

    This paper analyzes the effects of phase noise in multi-user OFDM systems. The impact on system performance of different phase noise characteristics and received power among users is considered. The main conclusion that can be achieved is the importance of power control in order to avoid a near-fact effect. Besides, the presence of transceivers with bad phase noise characteristics can ruin the performance of better (more expensive) ones. View full abstract»

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  • Digital rights management for visual content in mobile applications

    Page(s): 95 - 98
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1584 KB) |  | HTML iconHTML  

    With the emergence of wide bandwidth wireless networks, mobile Internet is set to provide a significant channel of multimedia content distribution. In the absence of proper digital rights management (DRM) systems, there is a real risk for content owners and producers to lose important revenues due to their intellectual property rights. To avoid market fragmentation and ensure interoperability, the Open Mobile Alliance (OMA) has set to define open DRM specification in their standardization process. In this paper, we review the specified methods of DRM within OMA. We present a scheme that utilizes watermarking as complementary solution for DRM on mobile devices, and we discuss how it could enhance the security of copyrighted media distribution. We focus the attention on the application of DRM methods for visual content in mobile devices. View full abstract»

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  • Neural networks and fuzzy nonlinear controllers applied to an induction machine

    Page(s): 483 - 486
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1544 KB) |  | HTML iconHTML  

    This paper is concerned by the use of neural networks and fuzzy logic for controlling a non-linear process namely an induction machine. In the first case study, the design procedure uses a neural model trained with the inverse model of the process. Thus, the overall controlled system is formed using this inverse model. In the second case study, a fuzzy logic controller is implemented. In both cases, the controller is cascaded with the process ensuring the robustness and the stability of the controlled system regarding parameters uncertainties and disturbances. This work analyses the advantages and the drawbacks of each controller in terms of tracking and regulation. It is shown that the fuzzy logic controller is slightly better with respect to the neural network controller in the transient while they have quite similar behaviour in the steady-state regime. View full abstract»

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  • PAPR reduction of coded OFDM signals based on iterative codeword construction

    Page(s): 763 - 766
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1523 KB) |  | HTML iconHTML  

    Orthogonal frequency division multiplexing (OFDM) allows transmission of data with high data rates over broadband radio channels without the need for powerful equalization. However, OFDM is sensitive to non-linearities in the system due to the high peak to average ratio (PAPR) in the transmitted signal. In this paper, we propose a simple method for reducing the PAPR in the OFDM signals using the well known BCH codes. The method relies on an iterative procedure to select a codeword that has a low PAPR from a translation of the code to another partition is loaded in the redundancy of the sent codeword and, therefore, no subcarriers are reserved for transmitting this information. The cost payed for this PAPR reduction is reduced error correction capability. Using this method, a reduction of the PAPR of up to 6 dB can be achieved with moderate complexity. View full abstract»

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  • An error correction strategy for digital audio watermarking scheme

    Page(s): 739 - 742
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1546 KB) |  | HTML iconHTML  

    Audio watermarking schemes are used in particular in order to embed imperceptibly data in digital audio signal. The analyzed audio watermarking scheme may be viewed as a particular communication system. However, due to the noise specificities (low SNR, piecewise stationarity, non Gaussianity), this scheme suffers of a very low BER (bit error rate). In this paper, we investigate an adequate error correction strategy based on the modification of the decoder metric. This modification is related to the a priori knowledge of the PDF (probability density function) of the noise. In this paper, the parametric generalized Gaussian distribution is used to piecewise model the time varying noise PDF. View full abstract»

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  • An adaptive equalizer for frequency modulated signals

    Page(s): 723 - 726
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1479 KB) |  | HTML iconHTML  

    The multiplicative scheme proposed for the demodulation of frequency modulated signals can deliver an error signal that, essentially, reflects the amplitude distortion of the transmission channel and, thus, can be used for blind adaptive equalization. The implementation of the corresponding LMS algorithm is discussed and illustrated by simulations. In fact, an alternative to the classical CMA approach is provided. The demodulation scheme, which belongs to the frequency discrimination family, is efficient since it requires no angle calculation or square root extraction and, in the various blocks , the sampling frequency can be chosen to minimize the computational complexity. View full abstract»

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  • Improved basic planar algorithm of vehicle guidance through waypoints by the line of sight

    Page(s): 541 - 544
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1504 KB) |  | HTML iconHTML  

    Guidance through waypoints is common for small autonomous marine vehicles. Guidance by the line of sight, the basic waypoint guidance algorithm, is very simple, computationally inexpensive, and flexible to sudden changes in the desired path specification. On the other side, the basic algorithm achieves unoptimal vehicle trajectory, ignores possible side disturbances as sea currents, and can even lead to deadlock situations. Therefore it should be improved to use in the real world applications. This paper introduces several such improvements: missed waypoint detection to prevent deadlocks, novel reference heading correction method to give smoother vehicle path in turns at waypoints, and sea current compensation method to cancel its influence. This improvements address the mentioned flaws of the basic algorithm, as is demonstrated by the simulations, and yet keep it simpler than is the case for the most used waypoint-derived guidance methods. View full abstract»

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  • Evaluation of SOVA algorithm in turbo code

    Page(s): 659 - 663
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1571 KB) |  | HTML iconHTML  

    The convolutional encoding with the Viterbi decoding algorithm represents one of the most popular techniques for direct error correction in the communication systems (forward error correction: FEC). This decoding technique has been proposed by A. Viterbi, it is based on maximum likelihood theory. The modification of this algorithm by introducing the soft value on the Viterbi algorithm makes it SOVA algorithm (soft output Viterbi algorithm), this modification gives the algorithm the possibility of quantifying the values of the received bits, so it will give more precise estimation of the decoded bit. The performance of the decoder will be from far more reliable. View full abstract»

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  • An authorization and access control model for workflow

    Page(s): 141 - 148
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1707 KB) |  | HTML iconHTML  

    A workflow is a coordinated arrangement of related tasks in an automated process, the systematic execution of which, ultimately achieves some goal. Workflow management systems (WFMSs) are becoming very popular and are being used to support many of the day to day workflows in large organizations. Workflow management systems are used for critical and strategic applications. Since, security is an essential and fundamental part of workflows, the workflow management system has to manage and execute the workflows in a secure way. Security, in a workflow context, involves the implementation of access control security mechanisms to ensure that tasks are performed by authorized subjects only. In this paper we propose a workflow authorization model capable of specifying authorization in such a way that subjects gain access to required objects only during the execution of the task. We build our model over the well known RBAC framework, and that in addition extends RBAC by including new rules in order to be adaptable with workflow context. View full abstract»

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  • Signal processing of vibrations for condition monitoring of an induction motor

    Page(s): 499 - 502
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1529 KB) |  | HTML iconHTML  

    Vibration monitoring is studied for fault diagnostics of an induction motor. Several features of vibration signals are compared as indicators of broken rotor bar of a 35 kW induction motor. Regular fast Fourier transform (FFT) based power spectrum density (PSD) estimation is compared to signal processing with higher order spectra (HOS), cepstrum analysis and signal description with autoregressive (AR) modelling. The fault detection routine and feature comparison is carried out with support vector machine (SVM) based classification. The best method for feature extraction seems to be the application of AR coefficients. The result is found out with real measurement data from several motor conditions and load situations. View full abstract»

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  • Optimization of extrapolated impulse response filters using semi-infinite programming

    Page(s): 397 - 400
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1458 KB) |  | HTML iconHTML  

    Narrow band lowpass or highpass digital finite impulse response filters can be synthesized by using extrapolated impulse response techniques to achieve reduced complexity. However, the non-linear optimization problem of the extrapolated impulse response filters was simplified to a linear programming problem in previous literature leading to suboptimum. In this paper, a semi-infinite programming is proposed to jointly optimize the filter coefficients and the extrapolated scaling factors. A realization structure making use of the coefficient symmetry is also presented. An example taken from literature is included illustrating that the number of multipliers for the resulting filter is less than 65 percent of existing results. View full abstract»

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  • Use of experience plans optimisation method to design CMOS low noise amplifier for UMTS application

    Page(s): 331 - 334
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1551 KB) |  | HTML iconHTML  

    This paper presents the design of a CMOS low noise amplifier (LNA) suited for UMTS wireless standard. This standard of third wireless generation aims to focus on the already existing process in order to develop and improve actual service systems capacitance, like cordless and satellite systems. This objective can be obtained by improving system gain, increasing transmission data rate, etc. The designed amplifier uses differential structure, to ensure linearity and low noise figure. The noise model in this circuit is well mastered, however non linearity phenomenon is still very hard to encounter. For this reason, heuristics methods couldn't be applied to make transistors and passive element's sizing. In order to obtain a trade between linearity and noise figure, we propose here to use an optimization method based on experience plans. We designed an LNA with AMS 0.35μm CMOS process. It provides a 19 dB gain at 2.14 GHz timing frequency and 2.4 dB noise figure (NF). The power consumption is 90 mW at 2.5 V power supply voltage. Simulation results are compared with the theoretical prediction and have shown the efficiency of our design methodology. View full abstract»

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