Uma Melhoria na Convergência do Método ICA-MAP para Remoção de Ruído em Sinal de Voz

Fabio Louvatti do Carmo, Evandro Ottoni Teatini Salles

DOI: 10.14209/sbrt.2013.137

Keywords: Speech Enhancement Maximum a posteriori MAP Independent Component Analysis (ICA) Non-Gaussian Noise Optimization

Abstract

This paper presents a modification to the ICA-MAP algorithm in order to improve its convergence. It was observed through testing that it is possible to limit the magnitude of the gradient vector, used to estimate the denoising model, and thereby improve the stability of algorithm. Such adaptation can be understood as a restriction the original optimization problem.

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Radar Meteorológico com Antenas Fixas: Projeto e Analise de Detector Ótimo

Marco Antonio Miguel Miranda, José Cândido Silveira Santos Filho, Gustavo Fraidenraich, Michel Daoud Yacoub, João Roberto Moreira Neto, Yusef Cáceres Zúñiga

DOI: 10.14209/sbrt.2013.138

Keywords: Weather radar Likelihood Ratio Detector Correlation Coefficient.

Abstract

In a recent paper, we have proposed a new lowcost framework for the construction of meteorological radars, by using two fixed widebeam antennas. In this work, we present the design of an optimal detector for this new kind of radar. The detector is designed according to the Neyman-Pearson criterion, based on the likelihood ratio of the signals received by the two antennas. Such a criterion, as well known, maximizes the detection probability for a given false-alarm probability. These probabilities are obtained in an exact closed form for the designed detector, as well as its performance is illustrated by numerical examples.

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Co-Channel Interference Effects On Spatial Multiplexing

Juan Carlos Minango, Celso de Almeida

DOI: 10.14209/sbrt.2013.144

Keywords: Spatial Multiplexing BER Co-Channel Interference.

Abstract

When spatial multiplexing (SM) technique is applied to a cellular system, the performance is affected by the interfer- ence from neighboring co-channel cells. This paper investigates and compares the performance between SM and non-SM systems in a noise-limited and interference-limited environment, where parameters related to the transmit power and spectral efficiency are taken into consideration, in order to make a fair comparison between the both systems. Monte Carlo simulations were per- formed for obtaining the results in terms of the bit error rate (BER) as a function of per-bit signal-to-noise ratio (E b /N o ) and signal-to-interference ratio (SIR).

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Bipartite HMM Model for Burst Errors Focused on the Generation of Gaps and Clusters

N. Maciel, Elaine C. Marques, M. Grivet, Ernesto L. Pinto

DOI: 10.14209/sbrt.2013.148

Keywords: Burst Error HMM ML Estimation

Abstract

A new Hidden Markov Model (HMM) for burst errors is proposed. This model is based on a compact representation of the error sequence in terms of succeeding pairs of clusters and gaps lengths. Its Markov chain has two classes of states associated to the generation of gaps and clusters lengths, respectively. The proposed model may be characterized by few parameters. An algorithm for ML (“Maximum Likelihood”) estimation of these parameters on the grounds of the EM (“ExpectationMaximization”) approach is derived. Some preliminary results of performance evaluation show that the model and the estimation algorithm here presented provide a flexible and efficient tool for capturing and reproducing statistics of interest in the context of burst errors modelling.

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Traditional, Lengthened and Shortened LT Codes Comparison

Guilherme R. Colen, Weiler A. Finamore, Moisés V. Ribeiro

DOI: 10.14209/sbrt.2013.145

Keywords: Shortened LT-codes Lengthened LT-codes Sys- tematic LT-codes Fountain Codes.

Abstract

Shortened and lengthened systematic Luby Trans- form Codes (LT-codes) have been shown, in this paper, to perform better than their equivalent mother codes by simulating trans- mission of LT-coded information over a binary erasures channel. The performance is improved as the shortening (lengthening) factor is increased while reducing (keeping) its complexity, when compared to the complexity of the mother code. The reported performance of both shortened and lengthened systematic LT- codes were obtained by designing the codes by using a truncated robust soliton degree distribution. Our results shows also that systematic LT-codes (despite the degree distribution) performs better than non-systematic LT-codes.

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Uma nova política de gerencia de buffer para Redes Tolerantes ao Atraso e Desconexões baseada em relações sociais

Camilo Souza, Edjair Mota, Leandro Galvao, Diogo Soares, Juliano F. Naves

DOI: 10.14209/sbrt.2013.149

Keywords: Delay and Disruption Tolerant Networks social relationship buffer management.

Abstract

Some types of Delay and Disruption Tolerant Networks (DTNs) need of humans help to send data between users. However, humans are socially selfishness and prefer to help users with whom they have a social relationship, fact that affects the network performance. Given the limited memory secondary space in the devices, the buffer management becomes a crucial factor to satisfactory network performance. This paper presents a novel buffer management policy for DTNs, based on social relationship strength between users. We evaluated this policy in conjunction with the Epidemic routing algorithm. The results show that this policy increases the delivery rate besides decreasing the average delay and the average number of hops in the evaluated scenario.

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Rede SDN-OpenFlow para o Caso de um ISP: Desafios e Oportunidades

Fernando López-Rodríguez, Divanilson R. Campelo

DOI: 10.14209/sbrt.2013.146

Keywords: Architecture ISP OpenFlow Robustness routing speed jitter traffic engineering overload controller dependence

Abstract

This article proposes an architecture for an ISP (Internet Service Provider) utilizing SDN-OpenFlow. With this, we attempt to create a network with less equipment processing and more traffic engineering potentiality than today’s one, and at the same time without the problems that might exist in networks implemented with OpenFlow, as controller overload, additional delays in flows creation and excessive controller network dependence.The following attributes have been taken into consideration in the design: network robustness requirements, routing speed response, jitter, delay, traffic engineering and equipment processing load.

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Demonstration of a Fiber Powered Extender for PON Applications

Rivael Strobel Penze, Joao B. Rosolem, Ulysses R. Duarte, Getulio E. R. Paiva, Renato Baldini Filho

DOI: 10.14209/sbrt.2013.150

Keywords: Optical access fiber powering optical fiber amplifiers optical fiber communications.

Abstract

This work proposes a new approach to powering PON extenders using the fiber powering technique, in order to make them virtually passives. In our demonstration, we show the feasibility of this technique applied to an SOA based extender for XG-PON/G-PON shared network reaching a distance of 50 km with a split ratio of 1:32. Results regarding the BER measurements and extender optical performance are discussed. This approach eliminates the batteries in the remote sites improving the reliability and the security of the system.

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Utilização de FRP variável para tratamento de zonas cegas em sistemas de radar de ruído pulsado

Bruno Pompeo, Leandro Pralon, Gabriel Beltrão

DOI: 10.14209/sbrt.2013.139

Keywords: radar systems noise radar waveform pulse repetition frequency

Abstract

This work addresses a method of eliminating blind zones and range ambiguity in monostatic pulsed radar systems. It is employed a combined use of Noise Radar (transmitted signals characterized by stochastic processes) and random pulse repetition frequency (PRFs). Finally, a comparison between the proposed method and conventional systems method - fixed pulse repetition frequency - is drawn.

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On the α-µ/Gamma Composite Distribution: Field Trials and Validation

Sérgio Pinho Piretti, Pedro Carlos Batista Bretas Jr., Ugo Silva Dias

DOI: 10.14209/sbrt.2013.140

Keywords: Composite Fading Channel Characterization Field Measurements α-µ/Gamma.

Abstract

This work proposes and conduct a practical investigation on the a probability density function of the α-µ/Gamma composite distribution, obtained in closed-form expression, for the multipath shadowed fading channel in wireless environments. The statistical characterization includes both theoretical models and practical investigations through field measurements. More specifically, the analyses was realized for the mobile radio channel operating in the frequencies 780 MHz, 1800MHz and 2500 MHz. A transmission and reception system was specially designed for field measurements and a software for processing the captured data was built. The practical data are confronted with the theoretical data obtained from the α-µ/Gamma distributions and very good fits are found.

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