Uma Abordagem para o Planejamento da Capacidade de Redes em Ambientes Competitivos com Base na Teoria de Jogos

Helio Waldman, Rodrigo C. Bortoletto

DOI: 10.14209/sbrt.2012.100

Keywords: telecommunication networks network dimensio- ning game-theory blocking probability Markovian model Nash equilibrium

Abstract

This paper discusses the network dimensioning strategies of two operating companies that supply channels to the same population of users based on a common infrastructure, in a competitive environment. The users wish to be serviced with minimum blocking probability, while the operators wish to maximize their profits. The resulting two non-cooperative games, respectively among the users and among the operators, are modeled and discussed. In the operators’ game, the effect of cost asymmetries is analyzed in order to determine the ability of an entrant to challenge a competitive monopoly as a function of his/her cost advantage.

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Algoritmos de Decodificação Abrupta para Códigos LDGM

Fernando Pujaico Rivera, Jaime Portugheis

DOI: 10.14209/sbrt.2012.101

Keywords: Error correcting codes Low density generator matrix codes Decoding algorithms Hard decision decoding

Abstract

Since Gallager introduced Bit-Flipping (BF ) deco- ding with hard-decision for Low-Density Parity-Check Codes (LDP C), other two variants were proposed by Sipser and Spielman for expander codes. Later, a soft-decision version of BF decoding, known as Modified Weighted BF (M W BF ) decoding, was investigated. This article proposes modified versions of Sipser and Spielman algorithms. Simulation results for long systematic Low-Density Generator Matrix (LDGM ) codes show a better performance of the proposed versions. Moreover, for moderate length systematic LDGM codes, simulation results show performance similar to that of MWBF decoding with the advantage of not requiring floating-point operations.

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Medida e Caracterização de Ambientes Indoor utilizando o algoritmo SAGE

Sérgio Augusto Costa Macedo, João P. Leite

DOI: 10.14209/sbrt.2012.79

Keywords: High resolution algorithms indoor channel measurements SAGE

Abstract

High resolution algorithms such as SAGE (Space Alternating Generalized Expectation Maximization) may be used to obtain the time response from a communication channel and, consequently, to obtain the power delay profile from environment. This paper presents a measure campaign by frequency sounding which employs SAGE to process these measurements, extracting the dispersion parameters for different indoor environments.

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Codificação eficiente de mapas de profundidade com base em predição e aproximação linear

Luı́s F. R. Lucas, Nuno M. M. Rodrigues, Carla L. Pagliari, Eduardo A. B. da Silva, Sérgio M. M. de Faria

DOI: 10.14209/sbrt.2012.103

Keywords: Depth map coding linear approximation predic- tive coding view synthesis

Abstract

This paper studies the problem of depth map compression for 3D video applications, based on virtual view synthesis. In this context, we propose an alternative algorithm to the current image coding standards, which avoids the known problems of depth map compression. The proposed algorithm is based on a flexible segmentation, combined with an hierarchical prediction step, that efficiently represent the objects’ sharp edges. The residue signal is approximated by a linear function. When compared to other alternative algorithms, the experi- ments show that depth maps compressed with our algorithm achieve state-of-the-art performance on virtual view synthesis.

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Aplicação do Algoritmo ISAT na Superamostragem de Sinais Bidimensionais

José Alexandre Nalon, Yuzo Iano

DOI: 10.14209/sbrt.2012.104

Keywords: ISAT algorithm Image processing Interpolation Supersampling

Abstract

There are numerous methods to increase pixel density in an image, many of them based in its frequency com- ponents, others based in computational intelligence techniques, among others. In this paper, we implement a supersampling method based on ISAT (In Situ Adaptive Tabulation). To assess the method’s efficiency, we compare the results of our simulations with classical techniques. While the algorithm here is presented with an emphasis on image processing, it could be used with signals with any dimensions.

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An Upper-Bound on the Ergodic Capacity of Rayleigh-Fading MIMO Channels using Majorization Theory

Antonio Alisson Pessoa Guimarães, Charles Casimiro Cavalcante

DOI: 10.14209/sbrt.2012.102

Keywords: Ergodic Capacity MIMO systems Rayleigh- fading Majorization Theory

Abstract

In this paper, we investigate the ergodic capacity of multiple-input multiple-output (MIMO) wireless communication systems over spatially uncorrelated Rayleigh-fading channels, assuming that the channel state information (CSI) is unknown at the transmitter and perfectly known at the receiver. Applying some results of majorization theory, we provide an analytical closed-form upper-bound to the ergodic capacity at any signal- to-noise ratio (SNR). In addition, we also derive an approximation to the ergodic capacity in high-SNR regimes. Finally, we present numerical results that confirm our theoretical analysis.

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Detecção de Pontos Fiduciais sobre a Face em Tempo Real

Felipe M. L. Ribeiro, Gabriel M. Araujo, Eduardo A. B. da Silva, José F. L. de Oliveira, Siome K. Goldenstein

DOI: 10.14209/sbrt.2012.87

Keywords: Computer Vision Object Detection Video Trac- king Face Tracking

Abstract

Recently, considerable attention has been given to the problem of robust detection and tracking of facial features. In this work, a framework for facial landmarks detection is presented. This framework is comprised by three interchangeable parts, namely preprocessing, classification and post-processing. In the classification stage, we used a cascade of classifiers based on correlation filters called IPD (Inner Product Detector). The resulting system is able to recognize facial landmarks on different subjects in real-time, under various lighting conditions. Details such as training of the detector employed, validation and usage are also discussed.

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Aplicação da Transformada de Kahunen e Loève na Compressão de Imagens Multiespectrais Usando a Recomendação do CCSDS

Oscavo G. Prata Jr, Marcelo S. Pinho

DOI: 10.14209/sbrt.2012.105

Keywords: —Compressão de dados compressão de imagens multiespectrais transmissão de imagens de sensoriamento remoto.

Abstract

This work proposes three different ways to apply the Kahunen and Loève Transform (KLT) in the algorithm for image compression recommended by CCSDS, in order to reduce the interband redundancy of multispectral images. The proposed schemes work with a fixed rate and have a simple algorithm to allocate the rate over the KLT components. The new methods are tested in a test set composed by four images from the CCD of CBERS-2B. The results show that these new methods can obtain an improvement over 2 dB when compared to the result of the CCSDS algorithm.

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Transmit/Receive Beamforming in Multiuser AF Relay Networks with Opportunistic Scheduling

Daniel Benevides da Costa, André L. F. de Almeida, C. Alexandre R. Fernandes

DOI: 10.14209/sbrt.2012.88

Keywords: Beamforming techniques cooperative communi- cations multiuser diversity opportunistic scheduling outage probability

Abstract

This paper evaluates the outage performance of multiuser relay networks in which the source and each one of the destinations are equipped with multiple antennas and employ beamforming techniques. More specifically, assuming Rayleigh fading channels and an amplify-and-forward relay, a general closed-form expression for the end-to-end outage probability is derived. Our analysis takes into account the benefits conferred by opportunistic scheduling in relay-assisted networks, where the source selects the destination with the strongest channel to schedule data transmission. The analytical results are validated by means of Monte Carlo simulation, and the effects of the relay placement and antenna configurations, on the overall system performance, are discussed through some representative numerical results and comparisons.

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Transformada Fracional do Cosseno em Corpos Finitos

Juliano B. Lima, Ricardo M. Campello de Souza, Paulo Hugo E. S. Lima

DOI: 10.14209/sbrt.2012.106

Keywords: Eigenvectors finite fields fractional transforms cosine transform

Abstract

In this paper, we present a definition for the fractio- nal cosine transform over finite fields. The proposed transform is derived from the knowledge of the eigenstructure of the discrete cosine transform and its relations with the eigenstructure of the discrete Fourier transform. A possible application of the new transform in the field of image encryption is discussed.

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