Empirical Investigation of Compressed Sensing applicability to Lossy Audio Compression

Rubem J. V. de Medeiros, Edmar C. Gurjão, João M. de Carvalho

DOI: 10.14209/sbrt.2010.37

Keywords: sampling audio compressed quality

Abstract

Compressive sampling is a new framework that exploits sparsity of a signal in a transform domain to perform sampling below the Nyquist rate. In this paper we investigate the applicability of the Compressed Sensing Framework to audio compression by searching for a good sparsity basis and a reconstruction technique fit to audio applications. We also propose a new method for lossy audio compression of real, non-sparse audio signals, based on our investigations. The method uses the Modified Discrete Cosine Transform (MDCT) as a sparse basis and the l-1 norm optimization for signal reconstruction. We evaluate final audio quality with the Perceptual Evaluation of Audio Quality (PEAQ) algorithm. The method we propose has the properties of reverse-complexity, cryptography, error-resiliency and universality of encoder, altogether without any additional hardware.

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Average Throughput Link Adaptation using HARQ Information and MIMO Systems

Cibelly Azevedo de Araújo, Walter Cruz Freitas Jr, Charles Casimiro Cavalcante

DOI: 10.14209/sbrt.2010.38

Keywords:

Abstract

In this article, we discuss about link adaptation (LA) for multiple-input multiple-output (MIMO) wireless systems. We present a cross-layer approach that takes into account a hybrid automatic repeat request (HARQ) information which is a medium access control layer (MAC) layer information. The expected throughput is then used in order to evaluate the influence of retransmissions in the average throughput. Therefore, we propose a modulation, coding and antenna scheme (MCAS) selection using HARQ information aiming to maximize the average throughput considering two different MIMO schemes: Alamouti and Bell labs layered space-time (BLAST).

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Feedback-Assisted Adaptive Network Coded Cooperation for Wireless Networks

Gean Marcos Geronymo, João Luiz Rebelatto, Bartolomeu F. Uchôa-Filho

DOI: 10.14209/sbrt.2010.110

Keywords: Cooperative communication LDPC network coding

Abstract

In this work, we propose a feedback-assisted version of the Adaptive Network Coded Cooperation (ANCC) scheme, recently proposed by Bao and Li for a network consisting of M users having independent information to send to a common base station. The aim is to increase the system rate without compromising its error performance, based on a small amount of feedback sent by the base station (only one bit for each received block is sufficient). Two different approaches are proposed. The expected rate is analyzed, and simulation results agree with the analytical ones. The system’s error performance is also evaluated through simulations, and we show that the performance is not degraded by the increase in the rate.

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A (Very) Brief Survey on Optimization Methods for Wireless Communication Systems

A. A. P. Guimarães, I. M. Guerreiro, L. M. C. Sousa, D. C. Moreira, T. F. Maciel, C. C. Cavalcante

DOI: 10.14209/sbrt.2010.111

Keywords: wireless communications optimization methods game theory majorization theory

Abstract

Wireless data usage is growing now faster than ever before. In order to attend the increasing demand for wireless services and considering that frequency spectrum is a scarce and expensive resource, wireless are required to operate as efficiently as possible. In this context, the application of mathematical optimization methods in the study and design of key functionalities of wireless systems has acquired great relevance. This papers surveys some applications of optimization methods to wireless communications problems. Among them, game theory and majorization theory have got increasing attention in the last few years and are described in some more details. An application of optimization methods to solve a concrete problem in modern wireless communications, namely, the maximization of the ergodic capacity of a Coordinated Multi-Point system with statistical Channel State Information at the Transmitter is also provided

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Assessing Strategies to Remove Back-to-Front Interference in Color Documents

Rafael Dueire Lins, Gabriel de França P. e Silva, João Marcelo Monte da Silva

DOI: 10.14209/sbrt.2010.39

Keywords: document back-to-front interference bleeding show-through quantitative method

Abstract

Whenever a document is written on both sides of translucent paper there is a back-to-front interference, also known as bleeding or show-through. In the literature there are many algorithms to filter out the back-to-front interference in documents. This paper presents a new quantitative method to assess those algorithms. This method is based on the synthesis of images with interference.

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A Turbo Coding Scheme for the 2-User Gaussian Adder Channe

M. L. M. G. Alcoforado, V. C. da Rocha Jr., M. J. de Carvalho Lima

DOI: 10.14209/sbrt.2010.40

Keywords: Turbo codes iterative decoding multiple access channel additive channel

Abstract

This paper discusses a coding scheme for the 2- user binary adder channel (2-BAC) employing a pair of distinct turbo convolutional codes, not necessarily forming a uniquely decodable code pair, in the presence of additive white Gaussian noise. The decoder is able to separate the binary data for each user by exploiting the code structure to combat noise and to resolve ambiguities, i.e., to distinguish between noisy versions of the two-user pairs (0;1) and (1;0). By means of computer simulation the performance of a particular pair of distinct turbo convolutional codes is determined and is presented as an example. The results are considerably better than those obtained by using a serial concatenation of 2-BAC uniquely decodable codes as outer codes and identical turbo convolutional codes as inner codes in the 2-BAC.

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Optical Amplitude Multiplexing through Parametric Amplification: An Analysis for the Idler Signal

A. L. A. Costa, J. D. Marconi, F. R. Barbosa, E. Moschim, M. L. F. Abbade

DOI: 10.14209/sbrt.2010.41

Keywords: Optical signal processing parametric amplifiers (PA) quaternary-amplitude shift keying (4 - ASK)

Abstract

Recently a new technique that used parametric amplification in optical fibers to combine two binary signals into a single quaternary amplitude-shift keying (4-ASK) signal, at frequency of signal to be amplified, was proposed. In this paper, other new technique with use of parametric amplification, also to combine two binary signals into a single quaternary amplitude-shift keying (4-ASK) it is proposed, however, the 4-ASK signal will be generated at idler frequency. We also develop a theoretical model to predict the power level distribution of the 4-ASK signals as a function of the extinction ratios of the input binary signals. Computer simulation results agree with the predictions of this theoretical model within a 1.3 dB margin. Finally, was also performed some simulation to compare the propagation between 4-ASK idler signal with 4- ASK probe signal. This technique could be applied to optically generate optical packets.

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Evaluation of the Effects of the Co-Channel Interference on the Bit Error Rate of Cellular Systems for BPSK Modulation

Daniel Altamirano, Celso de Almeida

DOI: 10.14209/sbrt.2010.42

Keywords: 2-PAM BPSK Co-Channel Interference SIR BER

Abstract

A performance analysis in terms of the bit error rate for digital systems with co-channel interference is done. In order to evaluate the effects of the interference on systems performance, expressions for the bit error rate are obtained for different scenarios. In these scenarios we consider one, two or K interferers that have the same power. If K is large, the interference is gaussian and the interference can be treated as equivalent noise. Scenarios with two interferers, where one of them is dominant and where the interference is asynchronous to the signal are also considered. Although the gaussian approximation is easy to be obtained, it is considered not a good model for cellular networks, because the number of main interferers is in essence one or two. This paper presents an effective tool to evaluate how much effective are the diverse schemes proposed to mitigate the co-channel interference in cellular networks.

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Implementation of PKIX-P2P with trust-based reputation using the JXTA platform

Francisco Sales de Lima Filho, Sergio Vianna Fialho

DOI: 10.14209/sbrt.2010.43

Keywords: P2P PKI PKIX Trust-based reputation Information Security Digital certification JXTA

Abstract

Nowadays, implement security in P2P systems is a great challenge. The possibility of building an infrastructure of public keys (PKI) operating in P2P environments represents a great advance. In this context, this paper presents an implementation of a P2P application with trust-based reputation using the JXTA platform.

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Hyperbolic lattices: a new propose for space time coding theory

Edson Donizete de Carvalho, Antonio Aparecido de Andrade

DOI: 10.14209/sbrt.2010.45

Keywords:

Abstract

In the context of space-time block codes (STBCs), the theory of hyperbolic lattices over totally real number field is presented, as well as theoretic criteria to check if such algebras are division algebras from arithmetic Fuchsian groups. These can be used to obtain families of 2 × 2 STBCs that satisfies the properties of linear dispersion, full rate and full diversity.

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