Dalton S. Arantes

Concurrent blind deconvolution for channel equalization

The constant modulus algorithm (CMA) is recognized as the most widely used algorithm in blind channel equalization practice. However, the CMA cost function exhibits local minima, which often leads to ill-convergence. This paper proposes a concurrent equalizer, in which a least mean square (LMS) equalizer operates cooperatively with a CMA equalizer, controlled through a non-linear link that depends on the system a priory state. Simulation results using M-QAM signalling have shown that the concurrent equalizer presents a much lower sensitivity to local minima than the CMA approach.

A fair scheduling discipline for Ethernet passive optical networks

We propose a novel policy called proportional sharing with load reservation (PSLR) for scheduling upstream flows in Ethernet passive optical networks. This policy provides bandwidth guarantees on a per flow basis and redistributes the unused bandwidth among active flows in proportion to their priority level.

On the performance of generalized processor sharing servers under long-range dependent traffic

This paper introduces the computation of delay and backlog bounds for a generalized processor sharing (GPS) server under long-range dependent (LRD) traffic. The traffic is supposed to be regulated by the Fractal Leaky Bucket policing mechanism, which is an appropriate regulator for LRD traffic. Results are extended to a network of GPS servers with arbitrary topology, and the stability of those networks is analysed.

Genetic decoding of linear block codes

This paper investigates the application of genetic algorithms to the decoding problem of error-correcting codes. The basic operations of crossover, mutation and selection are appropriately defined for the decoding problem of binary linear block codes without the knowledge of any algebraic structure. Simulation results indicate that these evolutionary techniques, if properly applied, can provide very interesting results for this difficult combinatorial problem. The result were obtained for hard-decision decoding of binary linear block codes, but the algorithms can be generalized to soft-decision decoding and to other kinds of linear codes. The algorithms presented are in fact evolutionary versions of the well known information set decoding.

8-VSB channel coding analysis for DTV broadcast

This article analyzes the channel coding stage in 8-VSB (8-level vestigial sideband) transmission for DTV (digital television) broadcast, proposed by ATSC (Advanced Television Systems Committee). We present BER (bit error rate) results for a codec simulator developed by the authors for the purpose of assessing the robustness of the ATSC 8-VSB coding stage in presence of an additive Gaussian noise channel and of impulsive channel noise surges. We discuss implementation aspects for the developed simulator.

Predictors for the discrete time fractional Gaussian processes

A discrete-time k-step predictor for fractional Gaussian noise is presented. Theoretical and simulated values of the normalized mean-square error are presented. Rules of thumb (Norros, 1995) are verified but in discrete time prediction. Furthermore, we deal with the problem of finding an estimate for the Hurst parameter H of the fractional Brownian motion (FBM) and with the problem of obtaining a complete prediction for the increments of the FBM in different instants and scales of time. We show that the wavelet analysis of the FBM is an appropriate tool for solving both of these problems. Several simulations are presented and comparisons with theoretical values are shown.

Interactive DSP course development/teaching environment

The authors have developed an interactive environment for the creation and maintenance of dynamic, active multimedia-based teaching mechanisms. The environment is designed to be user-friendly and to facilitate the creation of educational material. This tool has already been used to create courses in multidimensional signal processing (MDSP) by researchers working together while geographically separated.

On the performance of generalized processor sharing under long-range dependent traffic

It has been proved that it is possible to guarantee delay bounds in a generalized processor sharing (GPS) server when traffic is regulated by the leaky bucket algorithm. However, the leaky bucket is not an appropriate regulator for long-range dependent (LRD) traffic. This paper introduces the computation of backlog and delay bounds for a GPS server under LRD traffic. Traffic is assumed to be regulated by the fractal leaky bucket, which is proved to be an effective policing mechanism for LRD traffic.

MI-SBTVD: a proposal for the Brazilian digital television system SBTVD

The objective of this paper is to present a general overview of the Innovative Modulation System Project — MI-SBTVD — developed for the Brazilian Digital TV System. The MI-SBTVD Project includes an LDPC high performance error correcting code, an advanced transmit spatial diversity and an efficient multi-carrier modulation scheme. The building blocks of the system, its characteristics and most relevant innovations are presented. The performance of the whole system under different channels is compared with the performance of the present-day Digital Television standards. The complete system was implemented in FPGA using VHDL language and rapid prototyping tools for DSP algorithms.

Design, Simulation and Hardware Implementation of a Digital Television System: System Overview

In the year 2005 the Brazilian government supported many research consortia in order to develop an advanced digital television system employing the most recent technologies for multimedia broadcasting. One of the proposals for the physical layer of this system was entitled innovative modulation for the Brazilian digital TV system (MI-SBTVD). The MI-SBTVD project includes high performance error correcting codes, transmit spatial diversity and multi-carrier modulation. The aim of this paper is to present an overview of this innovative modulation system. The building blocks of the system, its characteristics and most relevant innovations are presented. The performance of the whole system under different channels is compared with the performance of the present-day digital television standards