In recent years, linear prediction voice encoders have become very efficient in terms of computing execution time and channel bandwidth usage while providing, in the absence of im- pulsive noise, natural sounding synthetic speech signals. This good performance has been achieved via the use of a maximum likelihood parameter estimation of an auto-regressive model of order ten that best fits the speech signal under the assumption that the signal and the noise are Gaussian stochastic processes. However, this method breaks down in the presence of impulse noise, which is common in practice, resulting in harsh or non-intelligible audio signals. In this paper, we propose a robust estimator of correlation, the Phase-Phase correlator that is able to cope with impulsive noise. Utilizing this correlator, we develop a Robust Mixed Excitation Linear Prediction encoder that provides improved audio quality for voiced, unvoiced, and transition speech segments. This is achieved by applying a statistical test to robust Mahalanobis distances for identifying the outliers in the corrupted speech signal, which are then replaced with filtered signals. Simulation results reveal that the proposed method outperforms in variance, bias, and breakdown point three other robust approaches based on the arcsin law, the polarity coincidence correlator, and the median- of-ratio estimator without sacrificing the encoder bandwidth efficiency and the compression gain while remaining compatible with real-time applications. Furthermore, in the presence of impulsive noise, the proposed speech encoder speech perceptual quality also outperforms the state of the art in terms of mean opinion score. / Doctor of Philosophy / Impulsive noise is a natural phenomenon in everyday experience. Impulsive noise can be analogous to discontinuities or a drastic change in natural progressions of events. Specifically in this research the disrupting events can occur in signals such as speech, power transmission, stock market, communication systems, etc. Sudden power outage due to lighting, maintenance or other catastrophic events are some of the reasons why we may experience performance degradation in our electronic devices. Another example of impulsive noise is when we play an old damaged vinyl records, which results in annoying clicking sounds. At the time instance of each click, the true music or speech or simply the audible waveform is completely destroyed. Other examples of impulse noise is a sudden crash in the stock market; a sudden dive in the market can destroy the regression and future predictions. Unfortunately, in the presence of impulsive noise, classical methods methods are unable to filter out the impulse corruptions. The intended filtering objective of this dissertation is specific, but not limited, to speech signal processing. Specifically, research different filter model to determine the optimum method of eliminating impulsive noise in speech. Note, that the optimal filter model is different for time series signal model such as speech, stock market, power systems, etc. In our studies we have shown that our speech filter method outperforms the state of the art algorithms. Another major contribution of our research is in speech compression algorithm that is robust to impulse noise in speech. In digital signal processing, a compression method entails in representing the same signal with less data and yet convey the the same same message as the original signal. For example, human auditory system can produce sounds in the range of approximately 60 Hz and 3500 Hz, another word speech can occupy approximately 4000 Hz in frequency space. So the challenge is, can we compress speech in one of half of that space, or even less. This is a very attractive proposition because frequency space is limited but the wireless service providers desires to service as many users as possible without sacrificing quality and ultimately maximize the bottom line. Encoding impulse corrupted speech produces harsh quality of synthesized audio. We have shown if the encoding is done with the proposed method, synthesized audio quality is far superior to the sate of the art.

In an extensive outdoor propagation study, low antenna heights of 1.7 m are used at both the transmitter and the receiver to measure over 3500 wideband power-delay profiles (PDPs) of the channel for a peer-to-peer communications system. Rural and urban areas are studied in 22 different transmitter-receiver links. The results are used to characterize the narrowband path loss, mean delay, root-mean-square (RMS) delay spread, and timing jitter of the peer-to-peer wideband channel. Small-scale fading characteristics are measured in detail by measuring and analyzing 160 PDPs within each local area. This thesis shows the measurement setup for the calculation of fading rate variance and angular spread and reports the first known attempt to calculate angular spread from track power measurements. New analysis presented in this thesis shows the effect of measurement error in the calculation of angular spread. The expected characteristics of angular spread are derived using two different angle-of-arrival (AOA) models from the literature. Measurement results show initial validation of Durgin's angular spread theory. A new measurement-based algorithm for simulating wideband fading processes is developed and implemented. This simulation technique shows promise in the simulation of high-bit rate peer-to-peer radio communication systems. / Master of Science

Wir stellen die Resultate einer Untersuchung von Strom-Strom-Korrelatoren beruhend auf den Grundprinzipien der Quantenchromodynamik vor. Wir benutzen die nicht-perturbativen Methoden der sogenannten twisted mass Gitter-QCD mit dynamischem up- und down-Quark unter Ausnutzung der automatischen O(a)-Verbesserung. Als Anwendung diskutieren wir die Berechnung des hadronischen Beitrags zur Korrektur in führender Ordnung in der elektromagnetischen Kopplung zum anomalen magnetischen Moment des Myons. Dieses gilt als eine sehr geeignete Größe für die aktuelle Suche nach neuer Physik jenseits des Standardmodells, besonders im Hinblick auf die Diskrepanz zwischen der Vorhersage aus dem Standardmodell und dem experimentell gemessenen Wert. Innerhalb der theoretischen Bestimmung ist der hadronische Anteil führender Ordnung mit der größten Unsicherheit behaftet und genießt derzeit somit naturgemäß Priorität. Wir beschreiben unsere Studie aller systematischen Unsicherheiten der Gitterrechnung auf Grundlage von drei Gittervolumina, zwei Gitterabständen, Pionmassen im Bereich von 650 MeV bis 290 MeV und den Quark-unverbundenen Beiträgen. Für die Extrapolation zum physikalischen Punkt stellen wir eine neue Methode vor, welche die Abhängigkeit von der Pionmasse hinreichend abschwächt und eine lineare Extrapolation ermöglicht. Im Ergebnis bestimmen wir den Beitrag von up- und down-Quark zu a_mu^hlo(N_f=2) = 5.69 (15) 10^(-8). Die dargelegten Methoden werden auf das Elektron- und das Tau-Lepton erweitert mit dem Resultat a_el^hlo(N_f=2) = 1.512 (43) 10^(-12) bzw. a_tau^hlo(N_f=2) = 2.635 (54) 10^(-6). Wir schätzen den Beitrag des charm-Quarks zu a_mu^hlo in der Partially Quenched tmLQCD mit dem Resultat a_mu^hlo(charm) = 1.447 (24) (30) 10^(-9) in Übereinstimmung mit der Vorhersage über die Dispersionsrelation unter Hinzunahme experimenteller Daten für das hadronische R-Verhältnis. / We present an investigation of hadronic current-current correlators based on the first principles of Quantum Chromodynamics. Specifically we apply the non-perturbative methods of twisted mass lattice QCD with dynamical up and down quark taking advantage of its automatic O(a) improvement. As a special application we discuss the calculation of the hadronic leading order contribution to the muon anomalous magnetic moment. The latter is regarded as a promising quantity for the search for physics beyond the standard model. The origin of the strong interest in the muon anomaly lies in the persistent discrepancy between the standard model estimate and its experimental measurement. In the theoretical determination the hadronic leading order part is currently afflicted with the largest uncertainty and a dedicated lattice investigation of the former can be of strong impact on future estimates. We discuss our study of all systematic uncertainties in the lattice calculation, including three lattice volumes, two lattice spacings, pion masses from 650 MeV to 290 MeV and the quark-disconnected contribution. We present a new method for the extrapolation to the physical point that softens the pion mass dependence of a_mu^hlo and allows for a linear extrapolation with small statistical uncertainty at the physical point. We determine the contribution of up and down quark as a_mu^hlo(N_f=2) = 5.69 (15) 10^(-8). The methods used for the muon are extended to the electron and tau lepton and we find a_el^hlo(N_f=2) = 1.512 (43) 10^(-12) and a_tau^hlo(N_f=2) = 2.635 (54) 10^(-6). We estimate the charm contribution to a_mu^hlo in partially quenched tmLQCD with the result a_mu^hlo(charm) = 1.447 (24) (30) 10^(-9) in very good agreement with a dispersion-relation based result using experimental data for the hadronic R-ratio.

Durant ces travaux, nous nous sommes intéressés à l’étude des transferts thermiques aux nano-échelles dans les couches minces par spectroscopie pompe-sonde femtoseconde. Dans un premier temps, nous nous sommes intéressés à la mesure haute-cadence de la conductivité thermique d’alliages de Fe-Si-Ge et Ti-Ni-Sn, dans le but d’optimiser leur processus de fabrication et de créer une base de données des propriétés thermiques de ces matériaux. Afin de pouvoir mesurer une grande quantité d’échantillons en un temps réduit, un système de mesure haute cadence entièrement automatisé a été développé et utilisé avec succès. Dans un second temps,ces travaux ont portés sur l’étude du transport thermique dans trois matériaux (Ge, GaAs In-GaAs) par spectroscopie pompe-sonde femtoseconde. Une nouvelle méthode de mesure de la réponse spectrale des nanomatériaux sur une gamme de fréquences allant de quelques centaines de kHz jusqu’au THz a été développée. Les mesures à l’aide de cette méthode ont permis de confirmer la présence d’un régime de transport qualifié de quasi-balistique dans certains matériaux,et une méthode d’extraction de propriétés thermiques à partir de la réponse spectrale mesurée, et prenant en compte ces effets quasi-balistiques, a été développée. L’ensemble des résultats obtenus par ces nouvelles méthodes confirment les travaux précédents décrits dans la littérature. Enfin, la mesure de la réponse spectrale d’un nano-matériau à haute fréquence est en grande partie limitée par la gigue des cavités lasers utilisées par l’expérience. Ainsi, la dernière étape a été de développer un système de mesure de cette gigue et de synchronisation de cavités laser qui pourra permettre de repousser la limite des fréquences mesurables par spectroscopie pompe-sonde femtoseconde. / In this work, we studied ultrafast thermal transport at nanoscale in thin films by femtosecond pump-probe thermal spectroscopy. We first developed a high-throughput heterodyne thermoreflectance setup that allows the extraction of thermal properties of a large number of sample in a minimum time, aiming at creating a database of these properties for a large numberof thin film ternary alloys with thermoelectric potential. In the second part of this work, wefocused on the study of thermal transport in three materials : Ge, GaAs and InGaAs. A high resolution phonon spectroscopy setup, along with a spectral reconstruction method allowed usto measure the response of these materials up to several tens of GHz in Fourier domain, which highlighted the presence of non-diffusive thermal transport in InGaAs. Non-diffusive theory,based on Lévy dynamics, allowed us to model this superdiffusion phenomenon and to extract coherent, frequency-independant thermal properties of these materials. Also, high frequency(>GHz) measurements of these spectral responses have shown interesting effects related to the ultrafast thermalisation in transducer-like very thin films. Finally, high-frequency thermal spectroscopy is inherently limited by the intrinsic timing jitter of laser cavities. Thus, the last partof this work was dedicated to developing a timing jitter measurement and active laser synchronisation system in order to increase the signal-to-noise ratio and access higher frequencies in pump-probe thermal spectroscopy experiments.

Made available in DSpace on 2016-06-02T19:03:58Z (GMT). No. of bitstreams: 1 5593.pdf: 13078959 bytes, checksum: 1cc88a226e87c0a4ca26af32176acea5 (MD5) Previous issue date: 2013-08-19 / Financiadora de Estudos e Projetos / The requirements imposed by the new applications presents great challenges to the computation. There is not a perfect computer architecture, capable to attend to all the requirements. The parallel and hybrid computer arrangement rise as a solution to this scenario i.e., the CPU-Coprocessor pair arrangement can form a specialized computerized instrument for a special application task. This doctoral thesis proposes a parallel and hybrid computational platform denoted CoP-WS, that uses the interoperability technology known as Web Services. As coprocessor it is used the graphic processing unit, known as the GPU, functioning recently as parallel thread level processing of general use applications. The platform test of feasibility was inspired in radio astronomy, and it has been implemented two applications: a complex correlator of signals provided by a radio interferometric arrangement, and a flare recognition system with a solar radio interferometer image. Both processings can be inserted in the context of pipeline execution, using sufficient configuration of CPU-GPU pairs, having on one side the interferometric arrangement antenna signal input and in the other side the result of the solar flare recognition. The obtained results of the both applications show the feasibility of the CoP-WS platform, for greater volume of data being processed in quasi real time. In the case of the correlator the average processing time in each integration period was around 160 ms, and in the case of the solar flare recognition, 48 ms for each solar disk image. / Os requisitos impostos pelas novas aplicações, sejam estas científicas, ou não, apresentam grandes desafios à computação. Não existe uma arquitetura de computadores "perfeita" que seja capaz de atender a todos estes requisitos. A configuração de arranjos paralelos e híbridos de computadores se apresenta como uma solução para este cenário, ou seja, a configuração de arranjos de pares CPU-Coprocessador, pode ser especializada para o processamento de uma aplicação distintas. Este trabalho de doutorado propõe uma plataforma computacional paralela e híbrida distribuída denominada CoP-WS, que utiliza a tecnologia de interoperabilidade conhecida como Web Services. Como coprocessador é utilizada a unidade de processamento gráfico conhecida como GPU, cuja função tem sido de processamento paralelo ao nível de threads, para aplicações gerais nos últimos tempos. A prova de viabilidade da plataforma implementada foi inspirada na radioastronomia, tendo sido implementados dois aplicativos: um correlacionador complexo de sinais provindos dos arranjos interferométricos e um sistema para o reconhecimento de explosões solares, numa imagem de radiointerferometria solar. Ambos os processamentos podem ser inseridos num contexto de execução em pipeline, usando uma configuração suficiente de pares CPU-GPU, tendo de um lado a entrada dos sinais das antenas do arranjo interferométrico e do outro lado o resultado do processamento de reconhecimento de explosões solares. Em ambas aplicações os resultados foram satisfatórios sendo que no caso do correlacionador o tempo médio de processamento de cada ciclo de integração foi de aproximadamente 160 ms, e para a aplicação de reconhecimento de explosões solares, de 48 ms por imagem de disco solar.

The subject of this work deals with the problem of channel estimation for CDMA systems. This method of multiple access when individual users share the same full bandwidth simultaneously and are differentiated with any of pseudorandom sequences, is now the most perspective method. That is proved by its wide implementation in mobile networks of the third generation and higher systems. This work describes basic theory principles of spread spectrum, above all DS-CDMA (Direct Sequence-CDMA) and furthermore some phenomena of radio wireless channel that affect changes in transmitted signal in its way from transmitter to receiver. Terms of fading, multipath propagation, loss, refraction, scattering of the wave and Rice and Rayleigh probability density functions are mentioned. The third chapter deals with yet known and used capabilities of channel estimation. Differences, advantages and disadvantages of so-called blind estimation or training-based estimation are discussed. Two algorithms: LS method and sliding correlator are analyzed in more detail. There is also description of their simulations in Matlab and some results of these simulations are discussed. The last chapter deals with comparison of main characteristics and achievable accuracy of wireless channel impulse response estimation by both methods, and their possible utilization in real live.

Ultra-wideband (UWB) communication technology offers inherent advantages such as the ability to coexist with previously allocated Federal Communications Commission (FCC) frequencies, simple transceiver architecture, and high performance in noisy environments. Spread spectrum techniques offer additional improvements beyond the conventional pulse-based UWB communications. This dissertation implements a multiple-access UWB communication system using a surface acoustic wave (SAW) correlator receiver with orthogonal frequency coding and software defined radio (SDR) base station transmitter. Orthogonal frequency coding (OFC) and pseudorandom noise (PN) coding provide a means for spreading of the UWB data. The use of orthogonal frequency coding (OFC) increases the correlator processing gain (PG) beyond that of code division multiple access (CDMA); providing added code diversity, improved pulse ambiguity, and superior performance in noisy environments. Use of SAW correlators reduces the complexity and power requirements of the receiver architecture by eliminating many of the components needed and reducing the signal processing and timing requirements necessary for digital matched filtering of the complex spreading signal. The OFC receiver correlator code sequence is hard-coded in the device due to the physical SAW implementation. The use of modern SDR forms a dynamic base station architecture which is able to programmatically generate a digitally modulated transmit signal. An embedded Xilinx Zynq ™ system on chip (SoC) technology was used to implement the SDR system; taking advantage of recent advances in digital-to-analog converter (DAC) sampling rates. SDR waveform samples are generated in baseband in-phase and quadrature (I & Q) pairs and upconverted to a 491.52 MHz operational frequency. The development of the OFC SAW correlator ultimately used in the receiver is presented along with a variety of advanced SAW correlator device embodiments. Each SAW correlator device was fabricated on lithium niobate (LiNbO3) with fractional bandwidths in excess of 20%. The SAW correlator device presented for use in system was implemented with a center frequency of 491.52 MHz; matching SDR transmit frequency. Parasitic electromagnetic feedthrough becomes problematic in the packaged SAW correlator after packaging and fixturing due to the wide bandwidths and high operational frequency. The techniques for reduction of parasitic feedthrough are discussed with before and after results showing approximately 10:1 improvement. Correlation and demodulation results are presented using the SAW correlator receiver under operation in an UWB communication system. Bipolar phase shift keying (BPSK) techniques demonstrate OFC modulation and demodulation for a test binary bit sequence. Matched OFC code reception is compared to a mismatched, or cross-correlated, sequence after correlation and demodulation. Finally, the signal-to-noise power ratio (SNR) performance results for the SAW correlator under corruption of a wideband noise source are presented.

Radio astronomy is the science of observing the heavens at radio frequencies, from a few kHz to approximately 300 GHz. In recent years, radio astronomy has faced a growing interference problem as radio frequency (RF) bandwidth has become an increasingly scarce commodity. A programmable real-time DSP least-mean-square interference canceller was developed and demonstrated as a successful method of excising satellite down-link signals from both an experimental platform at BYU, and the Green Bank Telescope at the National Radio Astronomy Observatory in West Virginia. A performance analysis of this cancellation system in the radio astronomy radio frequency interference (RFI) mitigation regime constitutes the main contribution of this thesis. The real-time BYU test platform consists of small radio telescopes, low noise RF receivers, and a state-of-the-art DSP platform. This programmable real-time radio astronomy RFI mitigation tool is the first of its kind. Basic tools needed for radio astronomy observations and the analysis and implementation of interference mitigation algorithms were also implemented in the DSP platform, including a power spectral density estimator, a beamformer, and an array signal correlator.