In this diploma thesis were created voice activity detectors according to the standard ITU-T G.729 and G.723.1. The voice activity detectors were implements in the digital signal processor TMS320C6416 made by Texas Instruments. At the same time detectors were designed using by MATLAB programming language. The diploma thesis can be divided into two parts. In the theoretical section provides information on how to report detectors in the standard ITU-T G.729 and G.723.1. In the implementation part is described steps in the implementation of the detector in signal processor TMS320C6416 and there are discussed various differences compared to the documentation.

The aim of this diploma thesis is to introduce methods of detection of the QRS complex and the subsequent detection of P waves. The intention is to create a program by specified method in the software Matlab which will be able to implement this method. The thesis describes the basic and important methods of detection and subsequent algorithm to detect P waves. Solution of the algorithm is tested on real data. It also describes the automatic signal evaluation and the results of this automatic function.

Dans cette thèse, nous développons une nouvelle méthode de détection de ruptures "Off-line", appelée Dérivée Filtrée avec p-value, sur des paramètres d'une suite de variables aléatoires indépendantes, puis sur le paramètre de Hurst d'un mouvement Brownien multifractionnaire. Cette thèse est composée de trois articles. Dans un premier article paru dans Sequential Analysis nous posons les bases de la méthode Dérivée Filtrée avec p-value (FDpV) en l'appliquant à une suite de variables aléatoires indépendantes. La méthode a une complexité linéaire en temps et en mémoire. Elle est constituée de deux étapes. La première étape utilisant la méthode Dérivée Filtrée détecte les bons instants de ruptures, mais également certaines fausses alarmes. La deuxième étape attribue une p-value à chaque instant de rupture potentiel détecté à la première étape, et élimine les instants dont la p-value est inférieure à un certain seuil critique. Nous démontrons les propriétés asymptotiques nécessaires à la calibration de la méthode. L'efficacité de la méthode a été prouvé tant sur des données simulées que sur des données réelles. Ensuite, nous nous sommes attaqués à l'application de la méthode pour la détection de ruptures sur le paramètre de Hurst d'un mouvement Brownien multifractionnaire. Cela s'est fait en deux phases. La première phase a fait l'objet d'un article à paraitre dans ESAIM P&S où nous avons établi un Théorème Central Limite pour l'estimateur du paramètre de Hurst appelé Increment Ratio Statistic (IRS). Puis, nous avons proposé une version localisée de l'IRS et démontré un TCL local pour estimer la fonction de Hurst d'un mouvement Brownien multifractionnaire. Les preuves sont intuitives et se distinguent par leur simplicité. Elles s'appuient sur le théorème de Breuer-Major et une stratégie originale appelée "freezing of time". La deuxième phase repose sur un nouvel article soumis pour publication. Nous adaptons la méthode FDpV pour détecter des ruptures sur l'indice de Hurst d'un mouvement Brownien fractionnaire constant par morceaux. La statistique sous-jacent de l'algorithme FDpV est un nouvel estimateur de l'indice de Hurst, appelé Increment Zero-Crossing Statistic (IZCS) qui est une variante de l'IRS. La combinaison des méthodes FDpV + IZCS constitue une procédure efficace et rapide avec une complexité linéaire en temps et en mémoire. / This Ph.D dissertation deals with "Off-line" detection of change points on parameters of time series of independent random variables, and in the Hurst parameter of multifrcational Brownian motion. It consists of three articles. In the first paper, published in Sequential Analysis, we set the cornerstones of the Filtered Derivative with p-Value method for the detection of change point on parameters of independent random variables. This method has linear time and memory complexities, with respect to the size of the series. It consists of two steps. The first step is based on Filtered Derivative method which detects the right change points as well as the false ones. We improve the Filtered Derivative method by adding a second step in which we compute the p-values associated to every single potential change point. Then we eliminate false alarms, i.e. the change points which have p-value smaller than a given critical level. We showed asymptotic properties needed for the calibration of the algorithm. The effectiveness of the method has been proved both on simulated data and on real data. Then we moved to the application of the method for the detection of change point on the Hurst parameter of multifractional Brownian motion. This was done in two phases. In the first phase, a paper is to be published in ESAIM P&S where we investigated the Central Limit Theorem of the Increment Ratio Statistic of a multifractional Brownian motion, leading to a CLT for the time varying Hurst index. The proofs are quite simple relying on Breuer-Major theorems and an original freezing of time strategy.The second phase relies on a new paper submitted for publication. We adapted the FDpV method to detect change points on the Hurst parameter of piecewise fractional Brownian motion. The underlying statistics of the FDpV technology is a new statistic estimator for Hurst index, so-called Increment Zero-Crossing Statistic (IZCS) which is a variation of IRS. Both FDpV and IZCS are methods with linear time and memory complexities, with respect to the size of the series.

The growth of multimedia content in recent years motivated the research on audio classification and content retrieval area. In this thesis, a general environmental audio classification and retrieval approach is proposed in which higher level semantic classes (outdoor, nature, meeting and violence) are obtained from lower level acoustic classes (emergency alarm, car horn, gun-shot, explosion, automobile, motorcycle, helicopter, wind, water, rain, applause, crowd and laughter). In order to classify an audio sample into acoustic classes, MPEG-7 audio features, Mel Frequency Cepstral Coefficients (MFCC) feature and Zero Crossing Rate (ZCR) feature are used with Hidden Markov Model (HMM) and Support Vector Machine (SVM) classifiers. Additionally, a new classification method is proposed using Genetic Algorithm (GA) for classification of semantic classes. Query by Example (QBE) and keyword-based query capabilities are implemented for content retrieval.

[pt] IoT refere-se a um sistema de dispositivos de computação inter-relacionados que visa transferir dados através de uma rede sem exigir interação humanohumano ou humano-para-computador. Esses sistemas de comunicação modernos, exigem restrições de baixo consumo de energia e baixa complexidade no receptor. Nesse sentido, o conversor analógico-digital representa um gargalo para o desenvolvimento das aplicações dessas novas tecnologias, pois apresenta alto consumo de energia devido à sua alta resolução. A pesquisa realizada em relação aos conversores analógico-digitais com quantização grosseira mostrou que esses dispositivos são promissores para o projeto de futuros sistemas de comunicação. Para equilibrar a perda de informações, devido à quantização grosseira, a resolução no tempo é aumentada através da superamostragem. Esta tese considera um sistema com quantização de 1 bit e superamostragem no receptor com um canal de downlink MIMO multiusuário com banda ilimitada e apresenta, como principal contribuição, a nova modulação de cruzamento de zeros que implica que a informação é transmitida no instante de tempo zero-crossings. Este método é usado para a pré-codificação temporal através da otimização do design da forma de onda para dois pré-codificadores diferentes, a maximização temporal da distância mínima até o limiar de decisão com forçamento a zero espacial e a pré-codificação MMSE no espácio-temporal. Os resultados da simulação mostram que a abordagem de cruzamento de zeros proposta supera o estado da arte em termos da taxa de erro de bits para os dois pré-codificadores estudados. Além disso, essa nova modulação reduz a complexidade computacional, permite dispositivos de complexidade muito baixa e economiza recursos de banda em comparação com o método mais avançado. Análises adicionais mostram que a abordagem do cruzamento de zeros é benéfica em comparação com o método mais avançado em termos de maior distância mínima até o limiar de decisão e menor MSE para sistemas com limitações de banda. Além disso, foi desenvolvido um esquema de mapeamento de bits para modulação de cruzamento por zero, semelhante à codificação de Gray para reduzir ainda mais a taxa de erro de bits. / [en] The IoT refers to a system of interrelated computing devises which aims to transfer data over a network without requiring human-to-human or humanto- computer interaction. This Modern communication systems demand restrictions of low energy consumption and low complexity in the receiver. In this sense, the analog-to-digital converter represents a bottleneck for the development of the applications of these new technologies since it has a high energy consumption due to its high resolution. The research carried out concerning to the analog-to-digital converters with coarse quantization has shown that such devices are promising for the design of future communication systems. To balance the loss of information, due to the coarse quantization, the resolution in time is increased through oversampling. This thesis considers a system with 1-bit quantization and oversampling at the receiver with a bandlimited multiuser MIMO downlink channel and introduces, as the main contribution, the novel zero-crossing modulation which implies that the information is conveyed within the time instant of the zero-crossings. This method is used for the temporal precoding through the waveform design optimization for two different precoders, the temporal maximization of the minimum distance to the decision threshold with spatial zero forcing and the space-time MMSE precoding. The simulation results show that the proposed zero-crossing approach outperforms the state-of-theart in terms of the bit error rate for both precoders studied. In addition, this novel modulation reduces the computational complexity, allows very low complexity devices and saves band resources in comparison to the state-ofthe- art method. Additional analyses show that the zero-crossing approach is beneficial in comparison to the state-of-the-art method in terms of greater minimum distance to the decision threshold and lower MSE for systems with band limitations. Moreover, it was devised a bit-mapping scheme for zero-crossing modulation, similar to Gray-coding to further reduce the bit error rate.