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  • 1.
    Casselgren, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Angular spectral response from covered asphalt2007Ingår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 46, nr 20, s. 4277-4288Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    By measuring the spectral reflection from the four different road conditions dry, wet, icy, and snowy asphalt, a method of classification for the different surfaces -- using two and three wavelengths -- is developed. The method is tested against measurements to ascertain the probability of wrong classification between the surfaces. From the angular spectral response, the fact that asphalt and snow are diffuse reflectors and water and ice are reflective are confirmed.

  • 2.
    Casselgren, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Model-based winter road classification2012Ingår i: International Journal of Vehicle Systems Modelling and Testing, ISSN 1745-6436, E-ISSN 1745-6444, Vol. 7, nr 3, s. 268-284Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An investigation of different road conditions has been conducted using a short-wave infrared (SWIR) light online sensor to examine the possibility of estimating road condition parameters such as porosity, depth and roughness. These parameters are essential for non-contact road friction estimation. The investigation show that it is possible to detect changes of depths of water and ice as well as classify different types of ice, by utilising polarised short-wave infrared (SWIR) light and a modified Hapke directional reflectance model

  • 3. Castro, Julio E.
    et al.
    Leblanc, James
    Rapajic, Predrag
    A multidimensional adaptive linear receiver for CDMA transmission corrupted by SD-MTI1999Ingår i: Asilomar Conference on Signal, Systems, and Computers, IEEE Communications Society, 1999, s. 927-930Konferensbidrag (Refereegranskat)
  • 4. Castro, Julio E.
    et al.
    Leblanc, James
    Rapajic, Predrag
    Multidimensional extension of MMSE linear adaptive receiver for DSSS systems1999Ingår i: Signal Processing and Its Applications: ISSPA '99. Proceedings, Piscataway, NJ: IEEE Communications Society, 1999, s. 915-918Konferensbidrag (Refereegranskat)
    Abstract [en]

    We extend the single channel adaptive linear receiver (ALR) to the multidimensional case. The extension is used for the cancellation of strong spatially-distributed narrowband interference in direct sequence spread spectrum communications. Simulations show a gain of 8 dB for the case of two interferences occupying 30% of the bandwidth of the spread spectrum signal

  • 5. Jr., C. Richard Johnson,
    et al.
    Bennett, P.C.E.
    Leblanc, James
    Krishnamurthy, Vikram
    Blind adaptive equalizer average stationary point stability analysis with admissibility consequences1992Ingår i: Proceedings of the 1992 Conference on Information Sciences and Systems, [March 18, 19, 20, 1992 at Princeton University], Princeton, NJ: Princeton University / Department of Electrical Engineering , 1992Konferensbidrag (Refereegranskat)
  • 6. Jr., C. Richard Johnson
    et al.
    Leblanc, James
    Krishnamurthy, Vikram
    Godard blind equalizer misbehavior with correlated sources: two examples1993Ingår i: Journal Marocain d'Automatique, d'Informatique et de Traitement du Signal, Vol. 2, s. 1-39Artikel i tidskrift (Refereegranskat)
  • 7. Krishnamurthy, Vikram
    et al.
    Dey, Subhrakanti
    Leblanc, James
    Blind equalization of IIR channels using hidden Markov models and extended least squares1995Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 43, nr 12, s. 2994-3006Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we present a blind equalization algorithm for noisy IIR channels when the channel input is a finite state Markov chain. The algorithm yields estimates of the IIR channel coefficients, channel noise variance, transition probabilities, and state of the Markov chain. Unlike the optimal maximum likelihood estimator which is computationally infeasible since the computing cost increases exponentially with data length, our algorithm is computationally inexpensive. Our algorithm is based on combining a recursive hidden Markov model (HMM) estimator with a relaxed SPR (strictly positive real) extended least squares (ELS) scheme. In simulation studies we show that the algorithm yields satisfactory estimates even in low SNR. We also compare the performance of our scheme with a truncated FIR scheme and the constant modulus algorithm (CMA) which is currently a popular algorithm in blind equalization.

  • 8. Leblanc, James
    Multichannel autoregressive modeling and spectral estimation methods for airborne radar environment: final report for Summer faculty research program - Rome Develoment Laboratory1996Rapport (Övrigt vetenskapligt)
  • 9. Leblanc, James
    On fractionally-spaced equalizer design for digital microwave radio channels1995Ingår i: Conference Record of the Twenty-Ninth Asilomar Conference on Signals, Systems and Computers, IEEE Communications Society, 1995, s. 290-294Konferensbidrag (Refereegranskat)
    Abstract [en]

    Advances in blind identification of fractionally-spaced models for digital communication channels and blind fractionally-spaced equalizer adaptation rely on the assumption that the time span chosen for the fractionally-spaced equalizer exceeds that of the channel. This paper considers time-domain design formulas minimizing the mean-squared symbol recovery error achieved by a finite-length FIR fractionally-spaced equalizer with a time span shorter than the channel impulse response time span for white zero-mean QAM sources in the presence of white zero-mean channel noise. For minimum mean-squared error designs the symbol error rates achievable are plotted versus the ratio of the source variance to the channel noise variance (with the channel model power normalized to achieve a received signal of unit variance) for different fractionally-spaced equalizer lengths on 64-QAM for several T/2-spaced channel models derived from experimental data. Our intent is to fuel the ongoing debate about fractionally-spaced equalizer length selection .

  • 10. Leblanc, James
    et al.
    Castro, Julio
    New Mexico State University.
    Model order selection for multidimensional innovations based detection in airborne radar1998Ingår i: Challenges in radar systems and solutions: proceedings of the 1998 IEEE Radar Conference, Dallas, Texas, May 11 - 14, 1998 / [ed] Scott Ramey, Piscataway, NJ: IEEE Communications Society, 1998, s. 141-146Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper investigates the model order selection problem for use with the multidimensional autoregressive (MAR) process in airborne radar detection processing which uses an innovations based detection algorithm (IBDA). Results indicate that a low order model should be used to accurately portray the return signal spectrum. Specifically, this paper investigates the use of the Akaike (1971) information criterion for model order selection. Examples are included for physically modeled data sets as well as actual radar data sets

  • 11. Leblanc, James
    et al.
    Chaine, M.D.
    Proximity effects of `unused' output buffers on ESD performance [CMOS]1991Ingår i: Reliability physics 1991: 29th annual proceedings, [1991 International Reliability Physics Symposium], Las Vegas, Nevada, April 9, 10, 11, 1991, New York: IEEE Communications Society, 1991, s. 327-330Konferensbidrag (Refereegranskat)
    Abstract [en]

    A unique failure mechanism, identified on an unused output buffer located near a used input protection device, occurs when excessive substrate current is generated during an electrostatic discharge (ESD) event. This new mechanism, the proximity effect, plays an important role when the n moat region of an input ESD circuit is within 20 μm of an unrelated n moat diffusion region contacted to the power supply, V cc. The operation of the most commonly used ESD input protection circuitry when stressed with respect to Vcc is reviewed. A laser cut experiment has verified that disconnecting the Vcc bus from the unused n moats eliminates this type of ESD failure. Device metal mask changes have confirmed these findings. This ESD failure mechanism, has been demonstrated on a variety of I/O buffer layouts, and a solution has been identified

  • 12. Leblanc, James
    et al.
    Chung, Wonzoo
    Cornell University, Ithaca.
    The local minima of fractionally-spaced CMA blind equalizer costfunction in the presence of channel noise1998Ingår i: Proceedings of the 1998 IEEE International Conference on Acoustics, Speech, and Signal Processing: May, 12 - 15, 1998, Washington State Convention and Trade Center, Seattle, Washington, USA, Piscataway, NJ: IEEE Communications Society, 1998, s. 3345-3348Konferensbidrag (Refereegranskat)
    Abstract [en]

    We study the local minima relocation of the fractionally spaced constant modulus algorithm (FSE-CMA) cost function in the presence of noise. Local minima move in a particular direction as the noise power increases and their number may be eventually reduced. In such cases the performance of FSE-CMA may fail to adequately reduce intersymbol interference (ISI), but achieve an approximated MMSE by reducing its equalizer noise gain under certain constraints. We analyze the mechanism of relocation of the FSE-CMA cost function local minima in terms of the auto-correlation matrix of the sub-channel convolution matrix and its eigenvectors

  • 13. Leblanc, James
    et al.
    Dogancay, K.
    Kennedy, Rodney A.
    Jr., C. Richard Johnson,
    Effects of input data correlation on the convergence of blind adaptive equalizers1994Ingår i: ICASSP-94: 1994 IEEE International Conference on Acoustics, Speech and Signal Processing, April 19 - 22, 1994, Adelaide Convention Centre, Adelaide, South Australia; [proceedings], Piscataway, NJ: IEEE Communications Society, 1994, s. III/313-III/316Konferensbidrag (Refereegranskat)
    Abstract [en]

    A variety of blind equalization algorithms exist. These algorithms, which draw on some theoretical justification for the demonstration or analysis of their purportedly ideal convergence properties, almost invariably rely on the input data being independent and identically distributed (i.i.d.). In contrast, in this paper we show that input correlation can have a marked effect on the character of algorithm convergence. We demonstrate that under suitable input data correlation and channels: (i) undesirable local minima present in the i.i.d. case are absent for certain correlated sources implying ideal global convergence for some situations and, (ii) the most commonly employed practical algorithm can exhibit ill-convergence to closed-eye minima even under the popular single spike initialization when an eye-opening equalizer parameterization is possible.

  • 14.
    Leblanc, James
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Fijalkow, Inbar
    University of Cergy-Pontoise.
    Blind adapted, pre-whitened constant modulus algorithm2001Ingår i: Where minds meet: 2001 IEEE International Conference on Communications ; ICC 2001. June 11 - 14, 2001 ; Helsinki ; conference re / [ed] Yrjö Neuvo, Piscataway, NJ: IEEE Communications Society, 2001, Vol. 8, s. 2438-2442Konferensbidrag (Refereegranskat)
    Abstract [en]

    We examine the use of a blind adaptive “pre-whitening” filter to precede an equalizer adapted by the constant modulus algorithm (CMA). The idea is based on results presented in which the use of a (fixed, or non-adaptive) pre-whitening filter provides an isometry (i.e. geometry preserving transformation) between the combined channel-equalizer (or global space) and the equalizer tap space. As much analysis found in CMA literature is done in “global space” now applies to the pre-whitened “equalizer tap space”, considerable exploitation of a known geometric structure is now possible. This paper’s main result demonstrates a method for improving the convergence rates of CMA adapted equalizers using the results of prewhitening analysis. The slow convergence of CMA equalizers is a common negative point associated with this well-known, robust blind equalization algorithm.

  • 15. Leblanc, James
    et al.
    Fijalkow, Inbar
    ENSEA/ETIS.
    Huber, Birkett
    Cornell University, Ithaca.
    Jr., C. Richard Hohnson,
    Cornell University, Ithaca.
    Fractionally spaced CMA equalizers under periodic and correlated inputs1995Ingår i: Conference proceedings ICASSP-95: ICASSP-95, Piscataway, NJ: IEEE Communications Society, 1995, s. 1041-1044Konferensbidrag (Refereegranskat)
    Abstract [en]

    CMA fractionally spaced equalizers (CMA-FSEs) have been shown, under certain conditions, to be globally asymptotically convergent to a setting which provides perfect equalization. Such a result relies heavily on the assumptions of a white source and no channel noise (as is the case in much of the literature's analysis of CMA). Herein, we relax the white source assumption and examine the effect of source correlation on CMA. Analytic results are meshed with examples showing CMA-FSE source correlation effects. Techniques for finding all stationary and saddle points on the CMA-FSE error surface are presented using recent developments in the algebraic-geometry community.

  • 16. Leblanc, James
    et al.
    Fijalkow, Inbar
    ENSEA/ETIS.
    Jr., C. Richard Johnson
    Cornell University, Ithaca.
    CMA fractionally spaced equalizers: stationary points and stability under i.i.d. and temporally correlated sources1998Ingår i: International journal of adaptive control and signal processing (Print), ISSN 0890-6327, E-ISSN 1099-1115, Vol. 12, nr 2, s. 135-155Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A common assumption in blind equalization schemes using the Constant Modulus Algorithm (CMA) is that the source sequence is an independent identically distributed (i.i.d.) sequence with equiprobable symbols. Much of the analysis demonstrating the global convergence of CMA in a noiseless channel to an open-eye setting uses this assumption. This work investigates the effect of source statistics (distributions and correlations) on the location of CMA stationary points in the fractionally sampled equalizer case under the conditions of equalizability. The work identifies the stationary points as the solution set of a system of multivariate polynomial equations with monomial coefficients given by the source moments.

  • 17. Leblanc, James
    et al.
    Fijalkow, Inbar
    ENSEA/ETIS.
    Jr, C. Richard Johnson,
    Cornell University, Ithaca.
    Fractionally-spaced constant modulus algorithm blind equalizer error surface characterization: effects of source distributions1996Ingår i: Conference Proceedings: ICASSP 96, Piscataway, NJ: IEEE Communications Society, 1996, s. 2944-2947Konferensbidrag (Refereegranskat)
    Abstract [en]

    The constant modulus algorithm (CMA) is a popular blind equalization algorithm. A common device used in demonstrating the convergence properties of CMA is the assumption that the source sequence is i.i.d. (independent, identically distributed). Previous results in the literature show that a finite length fractionally-spaced equalizer allows for perfect equalization of moving average channels (under certain channel conditions known as zero-forcing criteria). CMA has previously been shown to converge to such perfectly equalizing settings under an independent, platykurtic source. This paper investigates the effect of the distribution from which an independent source sequence is drawn on the CMA error surface and stationary points in the perfectly-equalizable fractionally-sampled equalizer case. Results include symbolic identification of all stationary points, as well as the eigenvalues and eigenvectors associated with their Hessian matrix. Results show quantitatively the loss of error surface curvature (in both direction and magnitude) at all stationary points. Simulations included demonstrate the affect this has on convergence speed.

  • 18. Leblanc, James
    et al.
    Gatine, G.
    Marquet, D.
    Management unit for reliable power supply stations for use in telecommunication facilities1989Ingår i: Eleventh International Telecommunications Energy Conference. INTELEC '89. Conference Proceedings, Poscataway, NJ: IEEE Communications Society, 1989, s. 9.3/1-9.3/4Konferensbidrag (Refereegranskat)
    Abstract [en]

    Following a general presentation of the system architectures for two types of reliable energy stations, GEODE and ALFATEL, used in telecommunication facilities, the authors describe the concept of a centralized management system covering several energy stations situated at different geographical locations. The role of communication with the power supply station monitoring units is then described. This makes it possible to define the functions carried out by the management unit, some of which may be operated through remote control by staff on standby duty. The functions of remote monitoring of processes, statistical studies, inventories, background records, man/machine relationships, and maintenance assistance are backed up by a PC-type machine .

  • 19. Leblanc, James
    et al.
    Jr, C. Richard Johnson
    Cornell University, Ithaca.
    Global CMA error surface characteristics, source statistic effects: polytopes and manifolds1997Ingår i: 1997 13th International Conference on Digital Signal Processing proceedings, Piscataway, NJ: IEEE Communications Society, 1997Konferensbidrag (Refereegranskat)
    Abstract [en]

    This work focuses on gaining insight to CMA behavior through identi cation of global properties of CMA stationary point locations due to source statistics (distributions and temporal correlation). The CMA error function under source correlation effects is viewed as a deformation of the iid CMA error surface. As deformations are the realm of topology, we look at some of the topological aspects connected with CMA source correlation. Some general characteristics of CMA under iid source are presented, noting relations to Morse Theory, polytopes, and Euler Characteristics.

  • 20. Leblanc, James
    et al.
    Jr., C. Richard Johnson,
    Toward operational guidelines for memoryless-error-function-style blind equalizers1992Ingår i: Proceedings 2nd COST 229 Workshop on Adaptive Algorithms in Communications, 1992, s. 5-17Konferensbidrag (Refereegranskat)
  • 21. Leblanc, James
    et al.
    Kennedy, Rodney A.
    Ryan, William E.
    Pre-cursor extended RAM-DFE canceler (PERC) nonlinear equalizer for nonlinear ISI channels1998Ingår i: Proceedings 1998 DSP Workshop, IEEE Signal Processing Society, 1998Konferensbidrag (Refereegranskat)
    Abstract [en]

    We consider a nonlinear equalizer structure that provides effective and computationally efficient intersymbol interference (ISI) reduction for channels with nonlinearities. The technique makes use of a RAM-DFE structure enhanced with the ability to cancel pre-cursor nonlinear ISI. In many nonlinear channels, the distortion caused by the nonlinear element (such as a nonlinear power amplifier) and bandlimiting filters creates nonlinear ISI. Such distortion typically limits the system to loworder constellations (such as QPSK). Higher order constellation are possible only if effective reduction of the nonlinear ISI is achieved. The applicability of our nonlinear equalizer and its performance for a nonlinear satellite channel is included.

  • 22. Leblanc, James
    et al.
    Leon, Philiph L. De
    New Mexico State University.
    Speech separation by kurtosis maximization1998Ingår i: Proceedings of the 1998 IEEE International Conference on Acoustics, Speech, and Signal Processing: May, 12 - 15, 1998, Washington State Convention and Trade Center, Seattle, Washington, USA, Piscataway, NJ: IEEE Communications Society, 1998, s. 1029-1032Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present a computationally efficient method of separating mixed speech signals. The method uses a recursive adaptive gradient descent technique with the cost function designed to maximize the kurtosis of the output (separated) signals. The choice of kurtosis maximization as an objective function (which acts as a measure of separation) is supported by experiments with a number of speech signals as well as spherically invariant random processes (SIRPs) which are regarded as excellent statistical models for speech. Development and analysis of the adaptive algorithm is presented. Simulation examples using actual voice signals are presented

  • 23. Leblanc, James
    et al.
    Léon, Philip L. De
    New Mexico State University.
    Source separation of speech signals using kurtosis maximization1997Ingår i: Proceedings of the 35th Allerton Conference on Communication, Control and Computing, University of Illinois Press, 1997Konferensbidrag (Refereegranskat)
  • 24. Leblanc, James
    et al.
    McLaughlin, Steven W.
    Enhanced RAM-based equalizers for nonlinear channels1999Ingår i: 32nd Asilomar Conference on Signal, Systems and Computers, IEEE Communications Society, 1999Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present a detection method for nonlinear channels with memory. This method uses a linear feedforward equalizer in conjunction with a random access memory (RAM) based (nonlinear) equalizer. The design criterion for the feedforward equalizer is non-traditional, with the intent to improve performance of the RAM-based equalizer. Development of the design criterion and a training-mode based adaptive implementation along with examples of this equalizer with a Pre-Cursor Enhanced RAM-DFE Canceller are included.

  • 25. Leblanc, James
    et al.
    McLaughlin, Steven W.
    Georgia Institute of Technology.
    Minimum mean square error channel truncation for magnetic channels1999Ingår i: Digest of INTERMAG 99, Piscataway, NJ: IEEE Communications Society, 1999, s. FS07-Konferensbidrag (Refereegranskat)
  • 26. Leblanc, James
    et al.
    McLaughlin, Steven W.
    Non-equiprobable constellation shaping and blind constant modulus algorithm equalization1996Ingår i: Proceedings of the 1996 Conference on Information Science and Systems : [CISS '96 held March 20,21, and 22, 1996 at Princeton University, Princeton, NJ], Princeton, NJ: Princeton University Press, 1996Konferensbidrag (Refereegranskat)
  • 27. Leblanc, James
    et al.
    Meyer, W.E.
    Blind adaptive fractionally-spaced CMA in the presence of channel noise1996Ingår i: Proceedings of the 1996 Conference on Information Science and Systems: CISS'96, 1996, s. 373-374Konferensbidrag (Refereegranskat)
  • 28.
    Leblanc, James
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Pääjärvi, Patrik
    Online adaptive blind deconvolution based on third-order moments2005Ingår i: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 12, nr 12, s. 863-866Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Traditional methods for online adaptive blind deconvolution using higher order statistics are often based on even-order moments, due to the fact that the systems considered commonly feature symmetric source signals (i.e., signals having a symmetric probability density function). However, asymmetric source signals facilitate blind deconvolution based on odd-order moments. In this letter, we show that third-order moments give the benefits of faster convergence of algorithms and increased robustness to additive Gaussian noise. The convergence rates for two algorithms based on third- and fourth-order moments, respectively, are compared for a simulated ultra-wideband communication channel.

  • 29. Leblanc, James
    et al.
    Raghuveer, M.
    New Mexico State University.
    Wavelet transform based detection of photon-limited and low contrast objects1997Ingår i: ICASSP 97: International Conference on Acoustics, Speech, and Signal Processing, Munich, Germany, April 21 - 24, 1997, Piscataway, NJ: IEEE Communications Society, 1997, s. 3657-3660Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents methods for detection and localization of photon-limited objects in noise. As opposed to the correlation based or Fourier transform based techniques which exhibit sensitivity to object scaling, we propose a method based on the continuous wavelet transform with its ability to reject noise and to localize objects in space and time as well as in scale. An advantageous twist presented here is the use of the wavelet transform on the complex envelope of the signal of interest. This has the advantage of reducing "rippling" effects seen in the transform of the original waveform. An example of further post-processing on the wavelet-transformed data is provided

  • 30. Lycksam, Henrik
    et al.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gren, Per
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Wiener filtering of interferometry measurements through turbulent air using an exponential forgetting factor2008Ingår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 47, nr 16, s. 2971-2978Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The problem of imaging through turbulent media has been studied frequently in connection with astronomical imaging and airborne radars. Therefore most image restoration methods encountered in the literature assume a stationary object, e.g., a star or a piece of land. In this paper the problem of interferometric measurements of slowly moving or deforming objects in the presence of air disturbances and vibrations is discussed. Measurement noise is reduced by postprocessing the data with a digital noise suppression filter that uses a reference noise signal measured on a small stationary plate inserted in the field of view. The method has proven successful in reducing noise in the vicinity of the reference point where the size of the usable area depends on the degree of spatial correlation in the noise, which in turn depends on the spatial scales present in the air turbulence. Vibrations among the optical components in the setup tend to produce noise that is highly correlated across the field of view and is thus efficiently reduced by the filter. © 2008 Optical Society of America.

  • 31. Marquet, D.
    et al.
    Leblanc, James
    RAMO: management network for telecommunications environment equipment1993Ingår i: 27-30 September 1993, Palais des Congres de Paris, France, 15ieme Conférence Internationale sur l'Énergie dans les Télécommunications, 15th International Telecommunications Energy Conference INTELEC '93, Paris: Sitecmo Dieppe , 1993, s. 173-177Konferensbidrag (Refereegranskat)
    Abstract [en]

    The RAMO network is the fundamental tool for operating the technical environment equipment of telecommunications centres which concern the power supply, cooling system, building surveillance, access control, security, EMC and electrostatic environment. It implements functions which make it possible to analyse the quality of the equipment's performance in operation, to precisely identify equipment failures to reduce their mean time to repair. The type of equipment included in this network varies depending on the size of the centre which houses it. It comprises the power supply systems, consisting of an electrical generator, an AC distribution cabinet, a conversion and power storage cabinet from the Alfatel range, catering for all power requirements from 2.5 kVA to 60 kVA, and from the Geode range for power greater than 100 kVA, together with the cooling systems and uninterruptible power supplies. The networking of all these items of equipment on an X.25 protocol using France Telecom's operating architecture comprises the RAMO network.

  • 32.
    Nilsson, Rickard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sjöberg, Frank
    Luleå tekniska universitet.
    Leblanc, James
    A narrow-band interference canceller for OFDM-based systems2001Ingår i: Proceedings EPMCC 2001, 2001Konferensbidrag (Refereegranskat)
  • 33.
    Nilsson, Rickard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sjöberg, Frank
    Luleå tekniska universitet.
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    A rank-reduced LMMSE canceller for narrowband interference suppression in OFDM-based systems2003Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 51, nr 12, s. 2126-2140Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a narrowband interference (NBI) canceller that suppresses spectral leakage in an orthogonal frequency-division multiplexing (OFDM)-based system caused by a narrowband (NB) signal. We assume that the spectrum of the NB signal is within the spectrum of the OFDM signal. This can be the case, e.g., on digital subscriber lines (DSL) and in new unlicensed frequency bands for radio transmission. The canceller makes linear minimum mean-square error estimates of the spectral leakage by measuring the NBI on a few modulated or unmodulated OFDM subcarriers. It uses a model of the NB signal's power spectral density as a priori information. Using a frequency invariant design, it is possible to cancel NBI from signals that are changing their frequency location with significantly reduced complexity overhead. The operational complexity of the canceller can be lowered by using the theory of optimal rank reduction and using the time-bandwidth product of the NB signal. Analytical performance evaluations, as well as Monte Carlo simulations, show that, without perfect a priori information, this canceller can suppress the spectral leakage from a strong NB signal (e.g., with equal power as the OFDM signal) to well below the background noise floor for typical applications where it causes negligible signal-to-noise ratio and symbol error rate degradation.

  • 34.
    Ovacikli, Aziz Kubilay
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik. Rubico Vibration Analysis AB.
    Pääjärvi, Patrik
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Skewness as an objective function for vibration analysis of rolling element bearings2014Ingår i: 2013 8th International Symposium on Image and Signal Processing and Analysis (ISPA 2013: Trieste, Italy, 4-6 Sept. 2013, Piscataway, NJ: IEEE Communications Society, 2014, s. 462-466Konferensbidrag (Refereegranskat)
    Abstract [en]

    The scale invariant third order moment, skewness, is analysed as an objective function to an adaptive gradient ascent algorithm. The purpose is to achieve a spectrum at the filter output that can enable identification of possible bearing defect signatures which are impulsive and periodic. Harmonically related sinusoids are used to represent such signatures and to build a signal model allowing characterization of the objective surface of skewness, providing insight to its convergent behaviour. The results are supported with an experiment from an industry setting. Robustness of the proposed algorithm is demonstrated by examining the frequency spectrum resulting from the signal model.

  • 35.
    Ovacikli, Kubilay
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik. Rubico Vibration Analysis AB.
    Pääjärvi, Patrik
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Uncovering harmonic content via skewness maximization: a Fourier analysis2014Ingår i: Proceedings of the 22nd European Signal Processing Conference (EUSIPCO 2014): Lisbon, Portugal, 1-5 Sept. 2014, Piscataway, NJ: IEEE Communications Society, 2014, s. 481-485, artikel-id 6952135Konferensbidrag (Refereegranskat)
    Abstract [en]

    Blind adaptation with appropriate objective function results in enhancement of signal of interest. Skewness is chosen as a measure of impulsiveness for blind adaptation to enhance impacting sources arising from defective rolling bearings. Such impacting sources can be modelled with harmonically related sinusoids which leads to discovery of harmonic content with unknown fundamental frequency by skewness maximization. Interfering components that do not possess harmonic relation are simultaneously suppressed with proposed method. An experimental example on rolling bearing fault detection is given to illustrate the ability of skewness maximization in uncovering harmonic content.

  • 36. Pääjärvi, Patrik
    et al.
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Blind equalization of PPM signals using third-order moments2007Ingår i: 2007 IEEE 8th Workshop on Signal Processing Advances in Wireless Communications: SPAWC 2007, Helsinki, Finland, 17 - 20 June 2007, Piscataway, NJ: IEEE Communications Society, 2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    In pulse-position modulation (PPM) signaling, the time location of short-duration pulses are used to convey information over a communication channel. For successful noncoherent reception, the channel duration must be short compared to the symbol interval. This paper analyzes the use of third moments in a blind adaptive equalizer setting to limit the effective delay spread of the channel. Results detail the global convergence properties of the proposed method, showing that the parameters approach ISI-free settings under general conditions.

  • 37. Pääjärvi, Patrik
    et al.
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Blind linear equalization of PPM signals using third-order moments2010Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 9, nr 4, s. 1298-1302Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel blind equalization strategy for pulse position modulation (PPM) based on maximizing the third-order moment of the equalizer output is presented. Compared to traditional fourth-order (e.g. kurtosis-based) methods, third-order moments give faster convergence and are less sensitive to noise. This work demonstrates that the intersymbol interference that plagues typical indoor ultra wideband (UWB) channels can be combatted using a third-moment maximizing blind equalizer which could therefore provide a cold start-up for a decision-directed scheme. Adaptation is shown to be asymptotically globally convergent with increasing time-hopped PPM frame length. Simulation experiments compare the performance to standard fourth-order schemes in practical settings, taking into account the conditions of time-hopping,multiple-access interference and a realistic UWB channel model.

  • 38. Pääjärvi, Patrik
    et al.
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Computationally efficient norm-constrained adaptive blind deconvolution using third-order moments2006Ingår i: 2006 IEEE International Conference on Acoustics, Speed [i.e. Speech] and Signal Processing: Toulouse, France, 14 - 19 May 2006, Piscataway, NJ: IEEE Communications Society, 2006, Vol. 3, s. 752-755Konferensbidrag (Refereegranskat)
    Abstract [en]

    Third-order central moments have been shown to be well suited as objective functions for blind deconvolution of impulsive signals. Online implementations of such algorithms may suffer from increasing filter norm, forcing adaptation under constrained filter norm. This paper extends a previously known efficient algorithm with self-stabilizing properties to the case of using a third-order moment objective function. New results herein use averaging analysis to determine adaptation stepsize conditions for asymptotic stability of the filter norm.

  • 39.
    Pääjärvi, Patrik
    et al.
    Rubico AB, Luleå.
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Fault-impact enhancement using adaptive filtering for condition monitoring of ball bearings2010Ingår i: The Seventh International Conference on Condition Monitoring and Machinery Failure Prevention Technologies: 22 - 24 June 2010, Ettington Chase, Stratford-upon-Avon, England ; CM 2010/MFPT 2010, Northampton: Coxmoor Publishing Co. , 2010, Vol. 1, s. 517-527Konferensbidrag (Refereegranskat)
    Abstract [en]

    A new signal pre-processing algorithm for condition monitoring of rolling bearings is presented. By enhancing the statistical asymmetry of a measured vibration signal, it is shown to enhance weak impacts from outer-and inner race defects to aid feature extraction and fault detection. Unlike many popular methods such as the high-frequency resonance technique (e.g. envelope analysis), the proposed algorithm is based solely on linear time-domain processing of lowpass vibration signals and hence does not rely on non-linear processing or on the potentially difficult task of selecting an appropriate frequency band for analysis. Consequently, low computational complexity as well as ease of use and implementation can be obtained. A key feature of the method is the enhancement of fault impulses in noisy and distorted measurement data series. This is accomplished through a novel type of adaptive filtering that selectively enhances transient impulses while simultaneously suppressing noise and disturbances. Numerical results are presented demonstrating the new algorithm applied to accelerometer data from industrial environments

  • 40. Pääjärvi, Patrik
    et al.
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Skewness maximization for impulsive sources in blind deconvolution2004Ingår i: Norsig 2004: proceedings of the 6th Nordic Signal Processing Symposium : June 9-11, 2004, Espoo, Finland / [ed] Jarmo M.A. Tanskanen, Helsinki: Helsinki University of Technology , 2004, s. 304-307Konferensbidrag (Refereegranskat)
    Abstract [en]

    In blind deconvolution problems, a deconvolution filter is often determined in an iterative manner, where the filter taps are adjusted to maximize some objective function of the filter output signal. The kurtosis of the filter output is a popular choice of objective function. In this paper, we investigate some advantages of using skewness, instead of kurtosis, in situations where the source signal is impulsive, i.e. has a sparse and asymmetric distribution. The comparison is based on the error surface characteristics of skewness and kurtosis.

  • 41. Ryan, William E.
    et al.
    Leblanc, James
    Kennedy, Rodney A.
    Performance study of RAM-based decision feedback equalizers with application to nonlinear satellite channels1999Ingår i: Signal Processing and its Applications: ISSPA '99. Proceedings, Piscataway, NJ: IEEE Communications Society, 1999Konferensbidrag (Refereegranskat)
    Abstract [en]

    The performance of nonlinear decision feedback equalizer implementations based on the use a random access memory (RAM) look-up table are considered. RAM look-up tables admit the modeling, without approximation, of the nonlinear intersymbol interference of nonlinear channels with finite memory. Three equalizers are considered; the RAM-DFE; RAM-canceler; and recently developed pre-cursor enhanced RAM-DFE canceler (PERC). In contrast to the classical “feedforward” Volterra equalizers, these equalizers have the advantage that the nonlinear processing element is out of the path of the noise, thus avoiding noise amplification. Results are presented for 16-QAM which compare and demonstrate the effectiveness of these equalizers, particularly the PERC, on the nonlinear satellite channel

  • 42.
    Sandberg, Sara
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Fréin, Cormac de
    University College Dublin.
    Leblanc, James
    Vasic, Bane
    University of Arizona.
    Fagan, Anthony D.
    University College Dublin.
    Performance of LDPC coded spread OFDM with clipping2005Ingår i: Proceedings of the 8th International Symposium on Communication Theory and Applications: ISCTA 2005, 2005, s. 156-161Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present the performance of OFDM systems with coding, spreading, and clipping. Low-Density Parity-Check (LDPC) codes give coding gains and spreading by the Walsh Hadamard transform gives gains in terms of increased frequency diversity as well as reduced peak-toaverage power ratio (PAPR) of the transmitted OFDM signal. By evaluating both the IFFT transform (OFDM) and the Walsh Hadamard transform in a single step, the number of operations needed for the spread OFDM system is actually less than for the conventional OFDM system. Reducing than for the conventional OFDM system. Reducing the PAPR is important in systems with clipping since it is related to the probability of clips. Each clip introduces clipping noise to the system which reduces the performance. Results of a clipped OFDM system with LDPC coding and spreading for an ETSI indoor wireless channel model are presented and compared with other systems. It is shown that there is a gain by spreading for LDPC coded OFDM systems, and especially for systems with clipping.

  • 43.
    Sandberg, Sara
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Performance degradation due to blindness in separation of MIMO-FIR systems over COST207 channels2005Ingår i: 13th European Signal Precessing Conference (EUSIPCO): 4 - 8 September 2005, Antalya, Turkey ; [proceedings], Antalya, 2005, s. 748-751Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper considers the performance penalty of a blind, compared to a non-blind, separation technique of a MIMO-FIR channel. In the blind method the mixing filters are first identified, while they are assumed to be known in the non-blind case. The blind system identification is performed using a recently proposed method based on cumulant subspace decomposition. Separation is then achieved by the FIR part of the mixing system inverse, which minimizes the cross-channel power. The performance penalty due to blindness is investigated for the case when the channel order is underestimated. Results of average residual cross-channel power of the wireless COST207 channel model are included.

  • 44.
    Sandberg, Sara
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Leblanc, James
    Vasic, Bane
    University of Arizona.
    Receiver-oriented clipping-effect mitigation in OFDM - a worthy approach?2005Ingår i: OFDM Workshop 2005, 2005Konferensbidrag (Refereegranskat)
    Abstract [en]

    The high peak-to-average power ratio (PAR) in Orthogonal Frequency Division Multiplexing (OFDM) modulation systems can significantly reduce performance and power efficiency. A number of methods exist that combat large signal peaks in the transmitter. Recently several methods have emerged that alleviate the clipping distortion in the receiver. We analyze the performance of two receiver clipping mitigation methods in an OFDM system with Cartesian clipping and low-density parity-check (LDPC) coding. Surprisingly, the cost of completely ignoring clipping in the receiver is minimal, even though we assume that the receiver has perfect knowledge of the channel. The results suggest that clipping mitigation strategies should be concentrated to the transmitter.

  • 45. Sehlstedt, Martin
    et al.
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    A computability strategy for optimization of multiresolution broadcast systems: a layered energy distribution approach2006Ingår i: IEEE transactions on broadcasting, ISSN 0018-9316, E-ISSN 1557-9611, Vol. 52, nr 1, s. 11-20Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper investigates the possible system gain for a multiresolution broadcast system using multilayer transmission of multiresolution data by utilizing nonuniform layer transmission energies. It shows how to find the energy distribution that maximizes the system performance, measured in the form of a sum of a weighted layer values /spl times/ population product (representing possible revenue for service providers). Through the introduction of the relative population coverage function P(a/sub i/) it is shown for a N layer system that in many cases when P(a/sub i/) is a concave function (equivalent to -P(a/sub i/) being convex) it is possible to reduce what seems to be an N-dimensional problem to N line searches. The paper also shows how the relative population coverage function can be constructed in two ways. The first uses analytic models for signal strength and population coverage (Uniform and Rayleigh). The second uses numerical signal strength and population estimates in grid format. The paper also includes examples to illustrate how the method works and the performance gain it provides. One of the examples uses actual grid estimates for an example transmitter located in Lulea, Sweden.

  • 46. Sehlstedt, Martin
    et al.
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Bit energy distribution effects in progressively encoded video frame transmissions2002Ingår i: Proceedings: IEEE International Conference on Multimedia and Expo : August 26 - 29, 2002, Swiss Federal Institute of Technology, Lausanne, Switzerland, Piscataway, NJ: IEEE Communications Society, 2002, Vol. 1, s. 269-272Konferensbidrag (Refereegranskat)
    Abstract [en]

    We investigate physical layer opportunities resulting from multimedia streams which use progressive coding. With such progressively encoded video frames the location of the first bit error is more important than the overall bit error probability. This makes the expected error free length a reasonable metric for performance optimization. One physical layer opportunity is the adjustment of bit energy within data frames. For wireless links nonuniform bit-energy distributions result in a flexible solution that may be used in conjunction with channel coding. We identify system gains to be achieved with nonuniform bit energy distribution optimizations and also show that a simplified frame truncation technique may be used without significant loss of quality.

  • 47. Sehlstedt, Martin
    et al.
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Distribution of multiresolution data using orthogonal broadcast channels: some design issues2004Ingår i: Gate to the global information society: 2004 IEEE International Conference on Communications ; ICC 2004 ; 20 - 24 June 2004, Paris, Piscataway, NJ: IEEE Communications Society, 2004, Vol. 5, s. 2837-2841Konferensbidrag (Refereegranskat)
    Abstract [en]

    Optimization of an N-layer digital multiresolution broadcasting system with respect to some form of quality/spl times/population product objective function appears to he an N-dimensional problem. However, with a generalized broadcasting model using N orthogonal channels with BPSK signaling under the assumption of uniform population distribution the problem can be narrowed down to three cases. This paper identifies each of these three cases and explains their meaning for system performance optimization.

  • 48. Sehlstedt, Martin
    et al.
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Nonuniform bit-energy distribution in wireless video frames2001Konferensbidrag (Refereegranskat)
    Abstract [en]

    For progressive frame based video data it is possible to use more bit-energy for important bits of the frame to increase the probability that these bits are transfered correctly in a wireless link. With a progressive bit stream the usual bit error probability is less important than the position measure of the first error within the frame. Here we propose the use of two alternate metrics to dynamically fine tune the performance for a link with a low data rate feedback channel by changing the bit-energy distribution in the transmitted signal and thereby aid unequal error protection.

  • 49. Sehlstedt, Martin
    et al.
    Leblanc, James
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Fransson, Pierre
    Jonsson, Andreas
    Schelén, Olov
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Forchheimer, Robert
    Linköpings universitet.
    Transparent cross-layer rate adaption of progressive multimedia streams for wired and wireless networks2005Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Real-time multimedia transfer through the Internet becomes more difficult when wireless links are in the path, due to the time varying channel capacity, from interference and multipath fading effects which introduce additional stochastic variations beyond the wireline network traffic effects. These wireless variations create problems for existing end-to-end rate adaption using feedback. This paper introduces a framework for cross-layer solutions to the streaming video problem with a focus on graceful degradation under network congestion and/or wireless fading effects without direct coordination between source coder, channel coder, and physical layer modulator. The solution presented includes network transportation and wireless based optimizations and requires little reliance upon end-to-end rate adaption. The suggested method uses progressively coded, leaky prediction source data and physical layer based rate adaption in concert with error tolerant network protocols.

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