Estimação Robusta do Desvio-Padrão de Ruídos Acústicos Aplicada ao Realce de Sinais de Voz

R. Tavares, R. Coelho

DOI: 10.14209/sbrt.2013.118

Keywords: speech enhancement robust estimation Ddimentional trimmed estimator

Abstract

This paper presents a method of speech enhancement performed in the time domain using a technique robust standard deviation. The technique was evaluated from three experiments, one using only the method and the other two as a proposal for post processing. The techniques used for the initial treatment applied to speech signals corrupted in the second experiment are SS (spectral subtraction) and IMCRA (improved minima controlled recursive averaging). The results presented by the gain of SegSNR indicate that the method provides a gain compared to IMCRA and SS compared individually. Already in experiment post-processing using the method in speech signals processed by SS showed gains, which did not occur as this method was applied to IMCRA.

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Codificação analógica via projeções de reticulados

Antonio Campello, Sueli I. R. Costa

DOI: 10.14209/sbrt.2013.121

Keywords: Analog Modulation Lattices Piecewise Linear Mappings

Abstract

In this paper we study a class of codes for the transmission of a discrete-time continuous alphabet source over a Gaussian channel. Our proposal differs from the ones found in the literature, that mostly deal with one dimensional continuous sources, in the sense that the scheme proposed here encodes sources with k-dimensional support to be transmitted over n-dimensional channels in the bandwidth expansion regime (n > k). The codes considered are associated to a piecewise continuous application. We describe the geometry of such codes, highlighting their connection with the search for good families of projections of the cubic lattice Zn. From this relation, we design an efficient decoding algorithm and exhibit some explicit construction with good simulation performance.

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Desempenho da Compressão de Imagens pra Transmissão de Imagens em Canais HF

Italo R. M. Soares, Edmar C. Gurjao, Francisco M. de Assis

DOI: 10.14209/sbrt.2013.122

Keywords: HF channel wavelet transform vector quantization modulation performance.

Abstract

Transmission in high-frequency (HF) is an alternative to high range and low cost systems, as image transmission in surveillance systems. Due to the effects of this channel in the transmitted signals and its low bandwidth, it is necessary to both use techniques to protect the transmitted signal (equalization , error control coding, etc.) and signal compression to reduce the representation of the source. In previous work, for image transmission in HF channels it was proposed the use of discrete wavelet transform and vector quantization, whose dictionary vectors must be directly mapped in points of a signal constellation. In this work we extend this work by using a more appropriated modulation to the HF channel and a specially projected dictionary. The modification here proposed has good results compared to other dictionary topology in low signal-to-noise situations.

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Data Compression and Sampling Period of Daily Energy Consumption

A. Carolina Flores, G. Fraidenraich

DOI: 10.14209/sbrt.2013.119

Keywords: Smart Grid Smart Meter data compression entropy.

Abstract

Data compression will be extremely necessary in order to solve the problem of large data volume generated by smart meters. The aim of this work, is to investigate the source coding theory, which establishes the entropy as a fundamental limit on the performance of conventional data compression algorithms applied to daily load curve of a typical resident consumer. We have proposed the applying of Pulse Code Modulation+Huffman and Differential Pulse Code Modulation+Huffman as methods to represent the consumption as few bits are possible, and we have explored the performance of compression when the typical sampling period of 15 minutes is reduced. Furthermore we have determined the second and third order entropies as a limit to data source compression schemes.

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Canais Matriciais Multiplicativos sobre Anéis de Cadeia Finitos

Roberto W. Nóbrega, Chen Feng, Danilo Silva, Bartolomeu F. Uchôa-Filho

DOI: 10.14209/sbrt.2013.123

Keywords: Anéis de cadeia finitos canais matriciais multiplicativos codificação de rede linear aleatória.

Abstract

Motivado pela perspectiva de codificação de rede na camada fı́sica baseada em reticulados aninhados, este artigo considera comunicação em canais matriciais multiplicativos sobre anéis de cadeia finitos. Tais canais são descritos pela expressão Y = AX, em que X e Y são as matrizes de entrada e saı́da, respectivamente, e A é a matriz de transferência. É assumido que as instâncias da matriz de transferência são desconhecidas pelo transmissor, mas disponı́veis ao receptor. Como contribuições, é obtida uma forma fechada para a capacidade do canal e é proposto um esquema de codificação que alcança a capacidade em complexidade de tempo polinomial. Os resultados aqui apre- sentados estendem os correspondentes para corpos finitos.

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Plataforma Computacional para Auxílio no Planejamento de Redes Celulares

Tales G. Fernandes, Renato A. Castellani, Ivan R. S. Casella

DOI: 10.14209/sbrt.2013.120

Keywords: Cellular Planning Wireless Communication

Abstract

This work presents a graphical computational simulation tool to aid in the planning of cellular networks. The developed platform makes possible to determine the received power and the signal-to-interference ratio in any position of the analyzed region for different clusters, terrains and propagation models. This platform can be used to promote future research to improve system quality and to increase the capacity of users.

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Análise de Campo do Acesso Web Por Meio de Uma Estrutura IP em Pilha Dupla

Deivis F. Pirani, Marcelo L. F. Abbade

DOI: 10.14209/sbrt.2013.41

Keywords: IPv6 Pilha Dupla HTTP Acesso Web Happy Eyeballs Análise de Campo Usuário Final.

Abstract

Este trabalho apresenta um estudo de campo sobre a comparação entre as utilizações do protocolo IPv4 e do IP em pilha dupla no acesso a páginas web. Para realizar tal análise, desenvolveu-se um conjunto de ferramentas capazes de coletar informações sobre o conteúdo e o desempenho destas páginas. Os resultados, relativos a mais de 19.000 acessos aos cinco portais de conteúdo mais visitados no Brasil, indicaram que, no pior caso, a utilização da pilha dupla causou um aumento de 32% no tempo médio de carregamento.

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Teaching DSP and Telecommunications with GNU Radio and Low Cost SDR Hardware

Joary Paulo, Francisco C. B. F. Muller, Andrey Silva, Aldebaro Klautau

DOI: 10.14209/sbrt.2013.126

Keywords: Education GNU Radio Software Defined Radio Low Cost SDR Platforms.

Abstract

Software defined radio (SDR) is an important tool for communication research nowadays. It allows for better spectrum utilization and leads to smarter communication systems. Besides, due to its flexibility, research groups have been using SDR hardware platforms for quicker implementation of new algorithms and development of products. Therefore, the availability of flexible and relatively low cost platforms has been increasing and can also be explored in the teaching environment. This work describes the GNU Radio platform and presents some GNU Radio scripts for public use in teaching basic and intermediate level aspects of communications systems. The goal of this initiative is to contribute to the telecommunications community with easyto-follow educational material that is made freely available.

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Plasmonic Fabry-Perot cavity for nano-optical filter and sensing platform

M. P. Cardoso, A. O. Silva, J. W. Costa

DOI: 10.14209/sbrt.2013.108

Keywords: Plasmonics Fabry-Perot cavity subwavelength optical filters optical sensors.

Abstract

This work deals with the nano-optical version of a Fabry-Perot cavity. By exciting plasmon modes on the metallic nanoparticles in the cavity, optical power can be squeezed into subwavelength scale without scattering effects stemmed from diffraction. As suggested by our first results, it surges feasible to use such structure as a building block for optical resonators at nanometer dimensions. Furthermore, the enhanced near-field provided by the plasmon modes yields a high-sensitive ultra- compact area, which meets potential applications for biochemical sensing.

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Super-Resolução para Síntese de Vistas em Ambientes de Resolução Mista

Camilo Dorea, Diogo C. Garcia, Ricardo L. de Queiroz

DOI: 10.14209/sbrt.2013.127

Keywords: Mixed resolution view synthesis super resolution

Abstract

Mixed resolution stereoscopic video is a popular format aimed at 3D content consumption. Nevertheless, resolution differences among views can pose significant drawbacks if adapting such a format to other multiview functionalities, such as view synthesis. In this paper we adjust standard view synthesis methodology to mixed resolution conditions. Operating within a mixed resolution, multi-view-plus-depth scenario, we then propose an improved super resolution method capable of enhancing lower-resolution views with high-frequency content available from neighboring full-resolution views. Results on publicly available data sets show that both strategies, adaptation of synthesis to asymmetry and direct enhancement of lowerresolution input views, can improve subjective and objective quality of synthesized views.

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