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Refereed/Peer-reviewed Underwater target localization is the most crucial part of the underwater wireless sensor network (UWSN). Due to limited communication range and energy constraints in underwater scenarios, only a subset of sensors can be selected to localize. This paper investigates the sensor selection schemes for hybrid angle-of-arrival (AOA) and time-of-arrival (TOA) localization in the underwater scenario. We first develop the Cramér-Rao lower bound (CRLB) for the hybrid AOA-TOA localization with correlated measurement noise model with Gaussian priors, and a Boolean vector is introduced to denote the selected sensors for hybrid measurement. Secondly, the sensor selection schemes are formulated as an optimization problem, and the optimality criterion is to minimize the trace of CRLB. The original nonconvex problem has been modified to the semidefinite problem program (SDP) by convex relaxation, and then, a randomization algorithm is chosen to advance the result of the SDP method. Finally, simulations verify that the proposed algorithm approaches the exhaustive search algorithm, and the effect of correlated measurement noise on the estimation performance in the hybrid localization system is proved.

The choice of an appropriate metric is mandatory to perform deformation analysis between two point clouds (PC)—the distance has to be trustworthy and, simultaneously, robust against measurement noise, which may be correlated and heteroscedastic. The Hausdorff distance (HD) or its averaged derivation (AHD) are widely used to compute local distances between two PC and are implemented in nearly all commercial software. Unfortunately, they are affected by measurement noise, particularly when correlations are present. In this contribution, we focus on terrestrial laser scanner (TLS) observations and assess the impact of neglecting correlations on the distance computation when a mathematical approximation is performed. The results of the simulations are extended to real observations from a bridge under load. Highly accurate laser tracker (LT) measurements were available for this experiment: they allow the comparison of the HD and AHD between two raw PC or between their mathematical approximations regarding reference values. Based on these results, we determine which distance is better suited in the case of heteroscedastic and correlated TLS observations for local deformation analysis. Finally, we set up a novel bootstrap testing procedure for this distance when the PC are approximated with B-spline surfaces.

In this paper, a novel robust sensor fault detection and isolation (FDI) strategy using the multiple model-based (MM) approach is proposed that remains robust with respect to both time-varying parameter uncertainties and process and measurement noise in all the channels. The scheme is composed of robust Kalman filters (RKF) that are constructed for multiple piecewise linear (PWL) models that are constructed at various operating points of an uncertain nonlinear system. The parameter uncertainty is modeled by using a time-varying norm bounded admissible structure that affects all the PWL state space matrices. The robust Kalman filter gain matrices are designed by solving two algebraic Riccati equations (AREs) that are expressed as two linear matrix inequality (LMI) feasibility conditions. The proposed multiple RKF-based FDI scheme is simulated for a single spool gas turbine engine to diagnose various sensor faults despite the presence of parameter uncertainties, process and measurement noise. Our comparative studies confirm the superiority of our proposed FDI method when compared to the methods that are available in the literature. 2016 Elsevier Ltd. All rights reserved. Scopus

Nowadays, mathematical model based estimation and control approaches are frequently consulted and applied for the treatment of such diseases. For the derived dynamics of the diseases, there are some states or internal variables which are very difficult to measure and needs very expensive measurement devices. Therefore, in this paper, adaptive unscented Kalman filter (AUKF) is designed for the state estimation of some vital diseases. These are Human Immunodeficiency Virus (HIV), Hepatitis-B virus (HBV) infection and Cancer such that unmeasurable states are estimated under measurement noises. The computational results show that accurate estimation of the unmeasured states are obtained and plotted for monitoring and control of possible future real-time applications. © 2018 IEEE.

Retinal blood vessel oxygenation is considered to be an important marker for numerous eye diseases. Oxygenation is typically assessed by imaging the retinal vessels at different wavelengths using multispectral imaging techniques, where the choice of wavelengths will affect the achievable measurement accuracy. Here, we present a detailed analysis of the error propagation of measurement noise in retinal oximetry, to identify optimal wavelengths that will yield the lowest uncertainty in saturation estimation for a given measurement noise level. In our analysis, we also investigate the effect of hemoglobin packing in discrete blood vessels (pigment packaging), which may result in a nonnegligible bias in saturation estimation if unaccounted for under specific geometrical conditions, such as subdiffuse sampling of smaller blood vessels located deeper within the retina. Our analyses show that using 470, 506, and 592 nm, a fairly accurate estimation of the whole oxygen saturation regime [0 1] can be realized, even in the presence of the pigment packing effect. To validate the analysis, we developed a scanning laser ophthalmoscope to produce high contrast images with a maximum pixel rate of 60 kHz and a maximum 30-deg imaging field of view. Confocal reflectance measurements were then conducted on a tissue-mimicking scattering phantom with optical properties similar to retinal tissue including narrow channels filled with absorbing dyes to mimic blood vessels. By imaging at three optimal wavelengths, the saturation of the dye combination was calculated. The experimental values show good agreement with our theoretical derivations.

Conference of ICU International Congress on Ultrasonics, ICU 2015 ; Conference Date: 11 May 2015 Through 14 May 2015; International audience; In the present work, the Synthetic Transmit Aperture (STA) imaging is applied on coarse grained steels using a contact phased-array probe. In order to reduce the noise introduced by the heterogeneous structure, as well as artifacts due to surface guided waves, the Decomposition of the Time Reversal Operator method is performed before calculating STA images.

One of the main challenges in indoor time-of-arrival (TOA)-based wireless localization systems is to mitigate non-line-of-sight (NLOS) propagation conditions, which degrade the overall positioning performance. The positive skewed non-Gaussian nature of TOA observations under LOS/NLOS conditions can be modeled as a heavy-tailed skew t-distributed measurement noise. The main goal of this article is to provide a robust Bayesian inference framework to deal with target localization under NLOS conditions. A key point is to take advantage of the conditionally Gaussian formulation of the skew t-distribution, thus being able to use computationally light Gaussian filtering and smoothing methods as the core of the new approach. The unknown non-Gaussian noise latent variables are marginalized using Monte Carlo sampling. Numerical results are provided to show the performance improvement of the proposed approach. © 2017, The Author(s).

Joint transmission (JT)-based Coordinated Multipoint (CoMP) systems achieve high performance gains by allowing full coordination among multiple cells, transforming unwanted intercell interference into useful signal power. In this paper, we present an analytical model to perform adaptive modulation for a typical JT CoMP system, consisting of three transmission points, under a target bit error rate (BER) constraint. Probability density functions of the signal-to-interference-plus-noise ratio (SINR) are derived for different JT CoMP schemes, and based on them, closed-form expressions for the average spectral efficiency (ASE) are obtained when adopting continuous-rate adaptive modulation. The study of ASE is also extended for the case of discrete-rate modulations, where the performance comparison of different practical quantized modulation schemes is carried out. © 2016 IEEE.

Retinal blood vessel oxygenation is considered to be an important marker for numerous eye diseases. Oxygenation is typically assessed by imaging the retinal vessels at different wavelengths using multispectral imaging techniques, where the choice of wavelengths will affect the achievable measurement accuracy. Here, we present a detailed analysis of the error propagation of measurement noise in retinal oximetry, to identify optimal wavelengths that will yield the lowest uncertainty in saturation estimation for a given measurement noise level. In our analysis, we also investigate the effect of hemoglobin packing in discrete blood vessels (pigment packaging), which may result in a nonnegligible bias in saturation estimation if unaccounted for under specific geometrical conditions, such as subdiffuse sampling of smaller blood vessels located deeper within the retina. Our analyses show that using 470, 506, and 592 nm, a fairly accurate estimation of the whole oxygen saturation regime [0 1] can be realized, even in the presence of the pigment packing effect. To validate the analysis, we developed a scanning laser ophthalmoscope to produce high contrast images with a maximum pixel rate of 60 kHz and a maximum 30-deg imaging field of view. Confocal reflectance measurements were then conducted on a tissue-mimicking scattering phantom with optical properties similar to retinal tissue including narrow channels filled with absorbing dyes to mimic blood vessels. By imaging at three optimal wavelengths, the saturation of the dye combination was calculated. The experimental values show good agreement with our theoretical derivations.

In this study, sign-error, sign-data, and sign-sign modifications of the multirate least mean squares (LMS) filter are proposed as an alternative to the existing multirate LMS and normalized LMS filters for reconstructing the high rate desired signal from its several low rate noisy observations. The performance of all the existing and the proposed methods are compared by using an adaptive noise cancellation simulation example applied to an audio signal. It is seen from the simulation results that some of the proposed methods lead to better results than the existing ones especially in the convergence speed sense. © 2016 IEEE.

Simultaneous measurement is considered for the working medium level and density by means of a system of two pressure sensors placed in the liquid at different levels and the use of a Kalman filter for filtering out the noise in this system. © 2007 Springer Science+Business Media, Inc.

Multirate adaptive filtering is related to the problem of reconstructing a high-resolution signal from two or more observations that are sampled at different rates. A popular existing method for solving this problem uses the multirate adaptive filter structure that is based on the least mean squares (LMS) approach. However, its low convergence rate restricts the use of this method. In this study, a multirate normalized LMS (NLMS) filter is proposed as an alternative to that of LMS based filter, for the reconstruction of the high-resolution signal from several low-resolution noisy observations. In the simulation example performed on an audio signal, it is observed that the proposed method leads to the better results than the existing method especially in the convergence rate. © 2015 IEEE.

This paper describes four experiments which have been carried out to evaluate the speech output component of the INSPIRE spoken dialogue system, providing speech control for di.erent devices located in a ‘‘smart’’ home environment. The aim is to quantify the impact of different factors on the quality of the system, when addressed either in the home or from a remote location (office, car). Factors analyzed in the experiments include the characteristics of the machine agent during the interaction (voice, personality), the physical characteristics of the usage environment (acoustic user interface, background noise, electrical transmission path), as well as task-related characteristics (listening-only vs. interaction situation, parallel tasks). The results show a significant impact of agent and environmental factors, but not of task factors. Potential reasons for this .nding are discussed. They serve as a basis for design decisions which have been taken for the final system.

We examine the effects of transmission-line nonidealities like series loss, terminal impedance mismatch, circuit noise, and transconductor input and output capacitances on the performance of traveling-wave (TWA) and transversal finite-impulse response (FIR) filters. A general framework is presented for the analysis and simulation of such filters in the context of a real communication channel. Simulation results for adaptive equalizers operating at a data rate of 10 Gbps are given. Intuition is derived for the vastly superior performance of TWA-FIR filters. We also show that the effects of series losses can be counteracted in some measure by deliberately misterminating the transmission lines with a resistance lower than their characteristic impedance. � 2006 IEEE.

A Monte Carlo simulation code has been developed in order to analyse avalanche gain and excess noise factor variation of the well-defined silicon avalanche photodiode (APD) geometry as a function of the neutron fluences up to 2 x 10(13) neutrons/cm(2). The results show that the neutron fluence has an influence on the excess noise factor for the same mean avalanche gain for the PbWO4 light. (c) 2005 Elsevier B.V. All rights reserved. Univ Florence; Ist Nazl Fis Nucl

The ridges obtained from chaotic signals can give the relevant information about the phase structures of the dynamical systems. Therefore, a new wavelet ridge determination method for the noisy signals and nonstationary signals, which is based on the singular value decomposition (SVD) has been proposed in this paper. The proposed method has been compared with Carmona method for monocomponent signals, and multicomponent signals. The proposed method is computationally more effective than the Carmona method to determine the actual ridges. Also, the ridges of the periodic limit cycles and chaotic attractors have been determined by using the SVD-based method to find the degree of chaoticity.

The basic principles and theory of phased subarray (PSA) imaging imaging provides the flexibility of reducing I he number of front-end hardware channels between that of classical synthetic aperture (CSA) imaging-which uses only one element per firing event-and full-phased array (FPA,) imaging-which uses all elements for each firing. The performance of PSA generally ranges between that obtained by CSA and FPA using the same array, and depends on the amount of hardware complexity reduction. For the work described in this paper, we performed FPA, CSA, and PSA imaging of a resolution phantom using both simulated and experimental data from a 3-MHz, 3.2-cm, 128-element capacitive micromachined ultrasound transducer (CMUT) array. The simulated system point responses in the spatial and frequency domains are presented as a means of studying the effects of signal bandwidth, reconstruction filter size, and subsampling rate on the PSA system performance. The PSA and FPA sector-scanned images were reconstructed using the wideband experimental data with 80% fractional bandwidth, with seven 32-element subarrays used for PSA imaging. The measurements on the experimental sector images indicate that, at the transmit focal zone, the PSA method provides a 10% improvement in the 6-dB lateral resolution, and the axial point resolution of PSA imaging is identical to that of FPA imaging. The signal-to-noise ratio (SNR) of PSA image was 58.3 dB, 4.9 dB below that of the FPA image, and the contrast-to-noise ratio (CNR) is reduced by 10%. The simulated and experimental test results presented in this paper validate theoretical expectations and illustrate the flexibility of PSA imaging as a way to exchange SNR and frame rate for simplified front-end hardware. Publisher's Version Q2 WOS:000226812800007 PubMed ID: 15742562

In this paper, we use the adjoint network theory to get quick estimates of the noise contributed by various elements in linear time-invariant opamp based circuits. The noisy operational amplifier is represented using a nullor with an input referred noise voltage and current source. The adjoint model for this representation is derived. This makes the noise analysis of operational amplifier based circuits very simple and the contribution of the operational amplifiers to the output noise can be obtained very often by inspection. The method is applicable to amplifiers, active RC and MOSFET-C filters. Examples of circuits analyzed include the universal active filter and gyrator topologies. ? 2004 IEEE.

Phase-shifting techniques in photoelasticity have a peculiar problem of isoclinic-isochromatic interaction, which lead to ambiguous zones in phase map. A comprehensive discussion on the reason for the formation of ambiguous zones is presented in this paper. A new method is developed to remove this ambiguity in the phase map. The new methodology is validated with theoretically and experimentally generated phase maps. A flexible algorithm for phase unwrapping is developed using tiling. The applicability of this is demonstrated using various benchmark problems consisting of simply and multiply connected bodies and slices cut from stress frozen models. ? 2004 Elsevier Ltd. All rights reserved.

This paper reports the design and testing of forward-viewing annular arrays fabricated using capacitive micromachined ultrasonic transducer (CMUT) technology. Recent research studies have shown that CMUTs have broad frequency bandwidth and high-transduction efficiency. One- and two-dimensional CMUT arrays of various sizes already have been fabricated, and their viability for medical imaging applications has been demonstrated. We fabricated 64-element, forward-viewing annular arrays using the standard CMUT fabrication process and carried out experiments to measure the operating frequency, bandwidth, and transmit/receive efficiency of the array elements. The annular array elements, designed for imaging applications in the 20 MHz range, had a resonance frequency of 13.5 MHz in air. The immersion pulse-echo data collected from a plane reflector showed that the devices operate in the 5-26 MHz range with a fractional bandwidth of 135%. The output pressure at the surface of the transducer was measured to be 24 kPa/V. These values translate into a dynamic range of 131.5 dB for I-V excitation in 1-Hz bandwidth with a commercial low noise receiving circuitry. The designed, forward-viewing annular CMUT array is suitable for mounting on the front surface of a cylindrical catheter probe and can provide Doppler information for measurement of blood flow and guiding information for navigation through blood vessels in intravascular ultrasound imaging. Publisher's Version Q2 WOS:000222678000018 PubMed ID: 15301009

We present a comparative study of high frequency dynamics and low frequency noise in elliptical magnetic tunnel junctions with lateral dimensions under 100 nm presenting current-switching phenomena. The analysis of the high frequency oscillation modes with respect to the current reveals the onset of a steady-state precession regime for negative bias currents above J = 10 7 A / cm 2, when the magnetic field is applied along the easy axis of magnetization. By the study of low frequency noise for the same samples, we demonstrate the direct link between changes in the oscillation modes with the applied current and the normalised low frequency (1/f) noise as a function of the bias current. These findings prove that low frequency noise studies could be a simple and powerful technique to investigate spin-torque based magnetization dynamics, We would like to acknowledge the support by the Spanish MINECO (MAT2012-32743), and the Comunidad de Madrid through NANOFRONTMAG-CM (S2013/MIT- 2850) and CCC-UAM (SVORTEX)

In this paper, we consider an amplify-and-forward hybrid satellite-terrestrial co-operative network in the presence of cochannel interference (CCI). More specifically, we assume that both the satellite-destination and the satellite-relay links undergo the shadowed-Rician fading and the relay-destination link follows the Nakagami-m fading. By applying the amplify-and-forward (AF) protocol at the terrestrial relay, both the relay and the destination are corrupted by cochannel interference from the terrestrial network. Based on this setup, we first derive the approximate statistical distributions signal-to-interference-plus noise ratio (SINR) and then analyze the system performance. To obtain more insights into the system performance, some asymptotical bit-error rate (BER) results are provided. Moreover, we extend our analysis to a multiple-relay network and analyze the asymptotic performance. Finally, some numerical results are provided to verify our analysis. Scopus

Future mobile networks are converging towards being heterogeneous, owing to the co-existence of multi-tier networks within the same geographical area, including macro, pico- and femto-cells. The deployment of such networks is generally based on user demand, which is irregular and random, implying that the deployment of base stations (BSs) is random as well. As a result, analyzing the communication protocols over heterogeneous networks (HetNets) is very challenging. A popular approach is to use stochastic geometry and treat the location of the BSs as points distributed according to a spatial Point Process. Most of the related work on the interference modeling normally assumes homogeneous Poisson point process (PPP). This assumption holds when the nodes are uniformly distributed in space, such as sensor networks or ad-hoc networks. Due to geographical factors, it may be the case for mobile users to cluster around highly populated cities and the PPP assumption does not provide an accurate model for the interference in these conditions. This motivates us to find better ways to characterize the aggregate interference when the transmitting nodes are clustered following a Poisson Cluster Process (PCP). Furthermore, the BSs belonging to different tiers may differ in terms of the transmit power, the node densities, and their link reliabilities. To this end, we consider K-tier HetNets, where, by using the Laplace transform approach, we characterize the aggregate interference at a given destination as a heavy-tailed distribution. Using the derived distribution, we investigate the probability of outage and coverage for such networks. Due to some difficulty in obtaining closed-form expressions for these measures, we derive tight bounds and verify that through numerical examples. We also compare the performance of HetNets when the nodes are clustered and otherwise. We observe that using the PPP results in larger success probability, but using the clustered process results in a larger coverage probability. We also observe that there is an optimal intensity, i.e., number of nodes, that achieves the maximum coverage probability for the given SINR (signal-to-interference-plus-noise ratio) threshold. Qatar National Research Fund Scopus

In this paper we present the excellent results obtained by mechanical decoupling of our thermal detectors from the cryostat. The starting point of this work is the necessity to improve the performances of thermal detectors and, besides, to eliminate the non-constant noise resulting from the overall cryogenic facility; this second point results to be crucial for rare-events experiments and the fundamental task for Dark Matter search. Tested on our bolometer, consisting of a 750 g tellurium oxide absorber coupled with an NTD thermistor and operated at &9 mK in an Oxford 200 dilution refrigerator, this powerful technique can, moreover, provide advantages for a large variety of thermal detectors. A good energy resolution of 3.9 keV FWHM was obtained for 2.615 MeV c-rays. The 4.2 keV average FWHM resolution for the 5407 keV 210Po a decay line is the best ever obtained for a-particles with any type of detector. ( 2000 Elsevier Science B.V. All rights reserved.

Cataloged from PDF version of article. Techniques to improve the accuracy of the finite-difference time-domain (FDTD) solutions employing sinusoidal excitations are developed. The FDTD computational domain is considered as a sampled system and analyzed with respect to the aliasing error using the Nyquist sampling theorem. After a careful examination of how the high-frequency components in the excitation cause sinusoidal steady-state errors in the FDTD solutions, the use of smoothing windows and digital low-pass filters is suggested to reduce the error. The reduction in the error is demonstrated for various cases.

This paper describes a new procedure for identification of plant parameters using limit cycles of specified period when output measurements are heavily corrupted by noise. A simple and elegant scheme is presented in which the plant output is not applied directly to the input of the relay to excite the limit cycles. Instead, the noise-corrupted error signal of the feedback control system is sampled, filtered through a special cyclic filter and a DC eliminator and then applied to the input terminal of the relay. The net result is a stable oscillation of definite period which is synchronous with respect to the sampling pulse train. Thus the effect of noise in the output measurements is easily eliminated. The cyclic filtering scheme enables simple on-line identification procedures such as the minimum norm and LSQ methods to be applied to yield highly accurate results. The dynamics of the cyclic filter introduced does not affect the parameters to be estimated in any manner. To accelerate the convergence of the parameters, the input to the system is also cyclically averaged. ? 1997 by John Wiley & Sons, Ltd.

The theory, design, and measured performance of an integrated circuit which enables closed-loop control of electrostatic micromotors is presented. The micromotor control integrated circuit (MCIC) consists of low-noise sense electronics designed to detect critical rotor angles to a resolution of 0.5/spl deg/ (0.05 fF) at a 1-MHz sampling rate, and control logic which cycles the micromotor drive state during continuous rotation to maintain maximum torque, independent of loading. Noise due to MOSFET switches and amplifiers in the analog section is modeled and shown to be 32 /spl mu/V referred to the system input, i.e., about half the desired switching resolution. The MCIC was fabricated using a 2-/spl mu/m, n-well CMOS process and functions as expected. The noise probability density function was measured using MCIC's digital output for different values of input-to-ground capacitance in order to verify the noise model. Good agreement with theory was observed, although the comparator exhibited some offset and hysteresis.

For the vector broadcast channel (BC), the case of erroneous channel state information (CSI) at the receiver is considered. Employing a well established lower bound for the mutual information with Gaussian signaling, a rate balancing problem is formulated where the rates of the different users are maximized under a transmit power constraint, but the rates of the different users have fixed ratios. A duality w.r.t. the signal-to-interference-and-noise ratio (SINR) between the vector BC with erroneous receiver CSI and an appropriately constructed vector multiple access channel (MAC) is established. Based on the observation that an interference function can be defined in the dual vector MAC that is standard, an iterative algorithm can be found for an appropriately formulated quality-of-service (QoS) optimization that is used for solving the balancing problem.

A numerical study was made at 1.5 ?m of high-concentration EDFAs pumped codirectionally and contradirectionally at various wavelengths. The model included the effects of signal upconversion and pump excited state absorption losses. An experimental verification of this study was made at the pump wavelength of 514 nm. The results of the experimental and numerical study show that contradirectional pumping gives lower gain and lower noise figures above a certain pump power, which is a function of fiber length and pump wavelength. ? 1996 John Wiley & Sons, Inc.

The Wigner-Ville distribution (WVD) has been a powerful signal processing tool for time-frequency signal analysis. Consequently, many algorithms have been proposed in the literature for computing the WVD in real-time applications [2, 8, 7, 5]. Recently, Pei and Yang proposed an efficient algorithm which uses discrete Hartley transform (DHT) to evaluate the WVD entirely in the real domain [5]. In this paper, a fixed-point error analysis of this algorithm has been carried out. An expression for output noise-to-signal ratio (NSR) is derived. The results indicate that this algorithm has better noise properties when compared to the FFT-based algorithm, even though the FFT has better noise properties than the FHT.

In long term evolution (LTE) systems, the achievable cell spectral efficiency is often limited by the inter carrier interference (ICI) or coverage shortage of base stations. Hence, in LTE-Advanced, cooperative communication has been proposed as an efficient technique to extend coverage, and improve throughput and link reliability. However, its performance gain is degraded in the presence of co-channel interference. In this paper, we propose cooperative communications scheme with interference management for LTE-A systems. The proposed scheme is based on best sub-channel selection (BSS) technique. BSS maximizes the received signal to interference plus noise ratio (SINR) for each orthogonal frequency-division multiplexing (OFDM) subcarrier while keeping the interference levels below a certain threshold. The scheme is using decoding and forward (DF) relaying protocol, and maximum ratio combined (MRC) receiver to combine the direct link (DL) and selected relaying signals. We derive exact closed form expressions of outage probability, ergodic capacity, and average bit error probability for the proposed scheme. In addition, we analysis the optimal sub-channel selection period for LTE-A system under users mobility. Simulations are used to validate the analytical expressions. The results confirm the advantage of the proposed scheme in enhancing interference management and link reliability. Scopus

Cellular networks are in a major transition from a carefully planned set of large tower-mounted base-stations (BSs) to an irregular deployment of heterogeneous infrastructure elements that often additionally includes micro, pico, and femtocells, as well as distributed antennas. In this paper, we develop a tractable, flexible, and accurate model for a downlink heterogeneous cellular network (HCN) consisting of K tiers of randomly located BSs, where each tier may differ in terms of average transmit power, supported data rate and BS density. Assuming a mobile user connects to the strongest candidate BS, the resulting Signal-to-Interference-plus-Noise-Ratio (SINR) is greater than 1 when in coverage, Rayleigh fading, we derive an expression for the probability of coverage (equivalently outage) over the entire network under both open and closed access, which assumes a strikingly simple closed-form in the high SINR regime and is accurate down to -4 dB even under weaker assumptions. For external validation, we compare against an actual LTE network (for tier 1) with the other K-1 tiers being modeled as independent Poisson Point Processes. In this case as well, our model is accurate to within 1-2 dB. We also derive the average rate achieved by a randomly located mobile and the average load on each tier of BSs. One interesting observation for interference-limited open access networks is that at a given SINR, adding more tiers and/or BSs neither increases nor decreases the probability of coverage or outage when all the tiers have the same target-SINR., Comment: IEEE Journal on Selected Areas in Communications, vol. 30, no. 3, pp. 550 - 560, Apr. 2012

金沢大学理工研究域電子情報学系, An associative memory using fixed and variable hysteresis thresholds in learning and recalling processes, respectively, has been proposed by authors. This model can achieve a large memory capacity and very low noise sensitivity. However, a relation between weight change Δ w and the hysteresis threshold ± T has not been well discussed. In this paper, a new learning algorithm is proposed, which is based on a delta rule. However, in order to stabilize the learning process, a method of using double hysteresis thresholds is proposed. Unit states are updated using ± T. The error, used for adjusting weights, is evaluated using ± (T+dT). This means 'over correction'. Stable and fast convergence can be obtained. Relations between η =dT/T and convergence rate and noise sensitivity are discussed, resulting the optimum selection for η. Furthermore, the order of presenting training data is optimized taking correlation, into account. In the recalling process, a threshold control method is further proposed in order to achieve fast recalling from noisy patterns.

Recent issues concerning low frequency aircraft noise around airports (groundnoise) and a legal verdict about the application of low frequency noise criteria in the Netherlands have been the motivation to start a research commissioned by the Dutch Ministry of Housing, Spatial Planning and the Environment. One of the objectives is to investigate the possibilities of the development of a rating procedure for low frequency noise. This paper gives an overview of the nature and impact of the low frequency groundnoise on the community, based on noise measurements and the experiences of residents around the airport. Keywords : low frequency noise, rating procedure, airport groundnoise, noise measurements, annoyance

An amplitude-modulated (AM) ultrasonic range finder using an online parameter estimation procedure is presented, which uses the sliding discrete Fourier transform (SDFT) algorithm for extracting the sinusoidal envelope from the received reference and ultrasonic signals. The received ultrasonic envelope contains an additive noise, which resembles another sine wave whose frequency is very close to that of the envelope. This gives rise to a low-frequency beat in the phase shift between the transmitted and received envelopes. Consequently, the estimated phase shows an equivalent phase jitter. The desired sinusoidal envelope signal cannot easily be separated from the noise signal, even by sharply tuned SDFT filters with phase-locked loops (PLLs). A parameter estimation procedure has been applied to remove these interharmonic signals with the help of comb filters. The PLL was strengthened by a cosine lookup table (LUT). By locating the envelope frequency far away from the interharmonic noise frequency, the convergence time could greatly be reduced. Simulation studies were conducted in the MatlabSimulinkDSP builder environment, and ideas were implemented in a Cyclone-II field-programmable gate array (FPGA)-based range finder fabricated in the laboratory. The test results of the AM ultrasonic range finder are presented to show its performance for static and slowly moving objects. � 2006 IEEE.

Recent issues concerning low frequency aircraft noise around airports (groundnoise) and a legal verdict about the application of low frequency noise criteria in the Netherlands have been the motivation to start a research commissioned by the Dutch Ministry of Housing, Spatial Planning and the Environment. One of the objectives is to investigate the possibilities of the development of a rating procedure for low frequency noise. This paper gives an overview of the nature and impact of the low frequency groundnoise on the community, based on noise measurements and the experiences of residents around the airport. Keywords : low frequency noise, rating procedure, airport groundnoise, noise measurements, annoyance

In this paper we propose a method of snectrum estimation using group delay functions. This method exploits the additive property of the Fourier transform (FT) phase to extract spectral information of the signal in the presence of noise. The phase is generally featureless due to random polarity and wrapping; but the group delay function can be processed to derive significant information such as peaks in the spectral envelope. In the spectral estimates obtained using this method, the resolution properties of the periodogram estimate are preserved while the variance is reduced. Variance caused by the sidelobe leakage due to windows and additive noise are significantly reduced even in the spectral estimate obtained using a single realization of the observation peak. Resolution is primarily dictated by the size of the data window according to the standard time bandwidth product relation. The method works even for high noise levels (SNR = 0 dB or less). The results of this spectrum estimation procedure are demonstrated through several illustrative examples. In particular, two cases are considered namely, 1) estimation of sinusoids in noise and 2) estimation of the narrow-band autoregressive process in noise. ? 1992 IEEE

In this paper we develop innovation-based adaptive Kalman filter (IAKF) based on linear time-varying (LTV) state-space model. Thorough argumentation of process and measurement noise covariance adaptation based on innovation sequence covariance is provided. As a result of implementing the proposed methods the process noise and measurement noise covariance matrices are adapted within a sliding window of a fixed depth. © 2009 IEEE. Russian Found. Basic Res. RBFR proj. 09-07-06004;Tomsk State University of Control Systems and Radioelectronics;Radar R and D

Low noise level is an essential feature when installing ventilation systems today. To achieve attenuation over a broad frequency range, the passive silencers traditionally used to attenuate ventilation noise can be combined with an active noise control (ANC) system. To insure reliable operation and desirable levels of attenuation when applying ANC to duct noise, it is highly important to be able to suppress the contamination of the microphone signals due to the turbulent pressure fluctuations arising as the microphones are exposed to the airflow in the duct. This paper is the first in a series of two, that treats the problem of turbulence induced noise originating from the airflow inside the ducts. Part I is concerned with theoretical and experimental investigations of the influence of the turbulence induced noise on the adaptive algorithm in the ANC system. Part II is concerned with design and investigations of microphone installations for turbulence suppression and results concerning the performance of an ANC system with the different microphone installations are presented. Some of the results were obtained at an acoustic laboratory according to an ISO-standard. The attenuation achieved with ANC was approximately 15-25 dB between 50-315 Hz even for airflow speeds up to 20 m/s. Also published in IJAV. The authors wish to acknowledge IIAV to which the copyrights are transferred to, for approving publication in this database as well.

Perception tests establish the effects of spatially band-limited noise and blur on human observer performance. Previously, Bijl showed that the contrast threshold of a target image with spatially band-limited noise is a function of noise spatial frequency. He used the method of adjustment to find the contrast thresholds for each noise frequency band. A noise band exists in which the target contrast threshold reaches a peak relative to the threshold for higher- or lowernoise frequencies. Bijl also showed that the peak of this noise band shifts as high frequency information is removed from the target images. To further establish these results, we performed forced-choice experiments. First, a Night Vision and Electronics Sensors Directorate (NVESD) twelve (12)-target infrared tracked vehicle image set identification (ID) experiment, second, a barpattern resolving experiment, and third, a Triangle Orientation Discrimination (TOD) experiment. In all of the experiments, the test images were first spatially blurred, then spatially band-limited noise was added. The noise center spatial frequency was varied in half-octave increments over seven octaves. Observers were shown images of varying target-to-noise contrasts, and a contrast threshold was calculated for each spatial noise band. Finally, we compared the Targeting Task Performance (TTP) human observer model predictions for performance in the presence of spatially band-limited noise with these experimental results.

The sliding discrete Fourier transform splits periodic signals into selected harmonic components, as on-line time functions. Ordinarily, the sampling frequency is equal to the product of the nominal signal frequency and the window width N. However, when the signal frequency drifts, to avoid the phase and magnitude errors, the sampling frequency can be adaptively adjusted using the phase-error itself. An integrated phase-locked loop scheme and its parameters like hold-in, pull-in ranges, lock time, steady-state errors are presented in this brief. � 2007 IEEE.

In photoelasticity, the method of obtaining the individual values of principal stresses/normal stresses separately is referred to as stress separation. Shear difference is one of the widely used techniques for stress separation in photoelasticity and one needs the value of fringe order and the isoclinic angle free of noise at every pixel over the domain. For accurate parameter determination, a ten-step phase shifting approach which uses a plane polariscope for isoclinic determination and a circular polariscope for isochromatic determination is proposed. A new quality guided approach for isoclinic unwrapping is developed. Isochromatic phasemap free of ambiguous zones is obtained by a new methodology and is unwrapped by a quality-guided approach. Whole field evaluation of stress components and its representation is then presented. The models used in this study are intentionally subjected to moderate loads showing a high level of isochromatic-isoclinic interaction. In view of this, the isoclinic data has several kinks which is found to cause streak formation in the whole field representation of separated stress components. An outlier smoothing algorithm is proposed for getting a smooth variation of the digital photoelastic parameters over the domain. Use of such smoothed data for stress separation has removed the streaks and has also greatly improved the accuracy of the separated stress components. � 2007 Elsevier Ltd. All rights reserved.

We present psychophysical data on the perception of static colored noise. In our experiments, we use the CIE94 color difference formula to quantify the noise strength and for describing our threshold data. In Experiment 1 we measure the visual detection thresholds for fixed pattern noise on a uniform background color. The noise was present in one of three perceptual color dimensions lightness (L*), chroma (C*), or hue (h). Results show that the average detection threshold for noise in L* is independent of hue angle and significantly lower than that for noise in C* or h. Thresholds for noise in C* and h depend on hue angle in an opponent fashion. The measured detection thresholds, expressed in terms of the components ?L*/kLSL, ?C*/kCSC, and ?H*/kHSH that build up the CIE94 color difference formula are used to tune CIE94 to our experimental conditions by adjusting the parametric scaling factors kL, kC, and kH. In Experiment 2, we measure thresholds for recognizing the orientation (left, right, up, down) of a test symbol that was incremental in L*, C*, or h, masked by supra-threshold background noise levels in L*, C*, or h. On the basis of the CIE94 color difference formula we hypothesized (a) a constant ratio between recognition threshold and noise level when the test symbol and background noise are in the same perceptual dimension, and (b) a constant recognition threshold when in different dimensions. The first hypothesis was confirmed for each color dimension, the second however, was only confirmed for background noise in L*. The L*, C*, h recognition thresholds increase with increasing background noise in C* or h. On the basis of some 16,200 visual observations we conclude that the three perceptual dimensions L*, C*, and h require different scaling factors (hue dependent for C* and h) in the CIE94 color difference formula, to predict detection threshold data for color noise. In addition these dimensions are not independent for symbol recognition in color noise. © 2008 Wiley Periodicals, Inc.

We present psychophysical data on the perception of static colored noise. In our experiments, we use the CIE94 color difference formula to quantify the noise strength and for describing our threshold data. In Experiment 1 we measure the visual detection thresholds for fixed pattern noise on a uniform background color. The noise was present in one of three perceptual color dimensions lightness (L*), chroma (C*), or hue (h). Results show that the average detection threshold for noise in L* is independent of hue angle and significantly lower than that for noise in C* or h. Thresholds for noise in C* and h depend on hue angle in an opponent fashion. The measured detection thresholds, expressed in terms of the components ?L*/kLSL, ?C*/kCSC, and ?H*/kHSH that build up the CIE94 color difference formula are used to tune CIE94 to our experimental conditions by adjusting the parametric scaling factors kL, kC, and kH. In Experiment 2, we measure thresholds for recognizing the orientation (left, right, up, down) of a test symbol that was incremental in L*, C*, or h, masked by supra-threshold background noise levels in L*, C*, or h. On the basis of the CIE94 color difference formula we hypothesized (a) a constant ratio between recognition threshold and noise level when the test symbol and background noise are in the same perceptual dimension, and (b) a constant recognition threshold when in different dimensions. The first hypothesis was confirmed for each color dimension, the second however, was only confirmed for background noise in L*. The L*, C*, h recognition thresholds increase with increasing background noise in C* or h. On the basis of some 16,200 visual observations we conclude that the three perceptual dimensions L*, C*, and h require different scaling factors (hue dependent for C* and h) in the CIE94 color difference formula, to predict detection threshold data for color noise. In addition these dimensions are not independent for symbol recognition in color noise. © 2008 Wiley Periodicals, Inc.

Perception tests establish the effects of spatially band-limited noise and blur on human observer performance. Previously, Bijl showed that the contrast threshold of a target image with spatially band-limited noise is a function of noise spatial frequency. He used the method of adjustment to find the contrast thresholds for each noise frequency band. A noise band exists in which the target contrast threshold reaches a peak relative to the threshold for higher- or lowernoise frequencies. Bijl also showed that the peak of this noise band shifts as high frequency information is removed from the target images. To further establish these results, we performed forced-choice experiments. First, a Night Vision and Electronics Sensors Directorate (NVESD) twelve (12)-target infrared tracked vehicle image set identification (ID) experiment, second, a barpattern resolving experiment, and third, a Triangle Orientation Discrimination (TOD) experiment. In all of the experiments, the test images were first spatially blurred, then spatially band-limited noise was added. The noise center spatial frequency was varied in half-octave increments over seven octaves. Observers were shown images of varying target-to-noise contrasts, and a contrast threshold was calculated for each spatial noise band. Finally, we compared the Targeting Task Performance (TTP) human observer model predictions for performance in the presence of spatially band-limited noise with these experimental results.

This work proposes a procedure for separating the 1/f noise from RTS noise in the time domain. The main advantage, respect to other methods, is that it does not assume a single hidden RTS, but it can extract the 1/f component even in presence of several RTS with different corner frequencies. The procedure has been validated through low-frequency noise measurements of the gate current in a MOSFET device.

The WiMAX standard specifies a metropolitan area broadband wireless access air interface. In order to support QoS for multimedia applications, various bandwidth request and scheduling mechanisms are suggested in WiMAX, in which a subscriber station can send request messages to a base station, and the base station can grant or reject the request according to the available radio resources. This article first compares two fundamental bandwidth request mechanisms specified in the standard, random access vs. polling under the point-to-multipoint mode, a mandatory transmission mode. Our results demonstrate that random access outperforms polling when the request rate is low. However, its performance degrades significantly when the channel is congested. Adaptive switching between random access and polling according to load can improve system performance. We also investigate the impact of channel noise on the random access request mechanism. © 2007 IEEE.

In this paper we consider the transmission of discrete data via a communication channel that is subject to (additive) noise with a known upper bound on its magnitude but otherwise completely unrestricted behavior. We are interested in the characterization of general conditions that allow perfect reconstruction of the discrete data (perhaps with some delay) under all possible realizations of channel noise and under a limit on transmission power. In particular, we investigate how linear preprocessing of the data and/or linear feedback from the receiver can be employed to aid perfect reconstruction, and we provide necessary conditions for improvements in perfect reconstruction in terms of ℓ1 norms of appropriate maps. Finally, we show that perfect reconstruction can be improved with feedback only if the feedback processing contains unstable poles. © 2007 IEEE. 2707 2712

Spectral representation of speech is complete when both the Fourier transform magnitude and phase spectra are specified. In conventional speech recognition systems, features are generally derived from the short-time magnitude spectrum. Although the importance of Fourier transform phase in speech perception has been realized, few attempts have been made to extract features from it. This is primarily because the resonances of the speech signal which manifest as transitions in the phase spectrum are completely masked by the wrapping of the phase spectrum. Hence, an alternative to processing the Fourier transform phase, for extracting speech features, is to process the group delay function which can be directly computed from the speech signal. The group delay function has been used in earlier efforts, to extract pitch and formant information from the speech signal. In all these efforts, no attempt was made to extract features from the speech signal and use them for speech recognition applications. This is primarily because the group delay function fails to capture the short-time spectral structure of speech owing to zeros that are close to the unit circle in the z-plane and also due to pitch periodicity effects. In this paper, the group delay function is modified to overcome these effects. Cepstral features are extracted from the modified group delay function and are called the modified group delay feature (MODGDF). The MODGDF is used for three speech recognition tasks namely, speaker, language, and continuous-speech recognition. Based on the results of feature and performance evaluation, the significance of the MODGDF as a new feature for speech recognition is discussed. � 2006 IEEE.

This document describes the apparatus and the procedure used to test the 1368 Multi Wire Proportional Chambers (MWPC) after front-end assembly for the LHCb Muon System. Given a fully equipped chamber, this system is able to diagnose every channel through an analysis of front-end output drivers and noise rate versus threshold response. In addition, it verifies if the noise rate at the operational threshold is within appropriate limits. Aiming at an automatic, fast and userfriendly system for mass production tests of MWPC, the project has foreseen as well electronic identification of every chamber and front-end board, and data archiving in such a way to make it available to the Experiment Control System (ECS). The results obtained on about 130 chambers tested are described.