Luis Geraldo Pedroso Meloni

Introduction to the Software-defined Radio Approach

Telecommunications have been in constant evolution during past decades. Among the technological innovations, the use of digital technologies is very relevant. Digital communication systems have proven their efficiency and brought a new element in the chain of signal transmitting and receiving, the digital processor. This device offers to new radio equipments the flexibility of a programmable system. Nowadays, the behavior of a communication system can be modified by simply changing its software. This gave rising to a new radio model called Software Defined Radio (or Software-Defined Radio - SDR). In this new model, one moves to the software the task to set radio behavior, leaving to hardware only the implementation of RF front-end. Thus, the radio is no longer static, defined by their circuits and becomes a dynamic element, which may change their operating characteristics, such as bandwidth, modulation, coding rate, even modified during runtime according to software configuration. This article aims to present the use of GNU Radio software, an open-source solution for SDR specific applications, as a tool for development configurable digital radio.

Digital TV and Distance Learning: Potentials and Limitations

One of the goals of the Brazilian Digital TV (DTV) system is to offer high-quality distance learning programs through DTV (t-learning). There are several differences between t-learning and e-learning that makes prohibitive just translate e-learning softwares to DTV. This paper presents the potentials that t-learning programs can achieve on countries with high digital divide, and also the limitations of t-learning environment. Different scenarios of DTV resource availability are also presented and its influence on t-learning potentials. With these scenarios we present some t-learning applications that were developed, among with an authoring tool for these applications. These studies are being conducted considering the previous experiences on Web-based learning programs

Return channel for the Brazilian digital television system-terrestrial

Recently, it has been proposed the use of WiMAX for the return channel in digital television systems using a new frequency profile bellow 1 GHz, which has been calledWiMAX-700. The profile operates from 400 MHz to 960 MHz as primary band, which includes the UHF band, and optionally from 54 MHz to 400 MHz as secondary band. This work presents some aspects of the WiMAX-700 technology and some simulation results of models designed to determine the system capacity concerning the number of actives subscriber stations, according to specific proposed scenarios, traffic sources profiles, specifics propagation, and coverage conditions. The results presented in this work provide elements to determine the suitability of WiMAX-700 technology as the return channel for the interactive digital television applications.

Software defined radio on digital communications: A new teaching tool

In this paper we present a Software Defined Radio (SDR) platform, composed by a USRP hardware and GNU Radio, as a new approach for teaching telecommunications at schools of Electrical Engineering. The proposed approach makes the preparation of an experiment faster by using modern communications architectures, which significantly reduce the occurrence of errors during the setup of test beds as well. This gives the students the opportunity to focus their efforts on the learning of communications techniques and algorithms. Furthermore, we intend to make easier the verification and validation processes of implemented models, supported by the use of specialized tools.

Learning Discrete Hidden Markov Models

This paper describes a learning program for discrete Hidden Markov Models (HMM). The learning of the theory of hidden Markov models is a hard task and many students have been disappointed after the first equations. This program attempts to facilitate the learning of the theory by means of a spread sheet interface for interactive user simulations. The spread sheet of observation probabilities simplify the understanding of several discrete HMM equations. The program allows the student to observe several convergence properties of the training algorithm.

WiMAX simulation models for return channel in digital television systems

Recently, it has been proposed the use of WiMAX for the return channel in digital television systems, but using a new frequency profile around 700 MHz. This work presents some simulation results of models designed to determine the system capacity concerning the number of active subscriber stations, and according to specific proposed scenarios, traffic sources profiles, and specific propagation and coverage conditions. The results presented in this work provide elements to determine the suitability of WiMAX technology as the return channel for the majority of interactive digital television applications. It also presents some conditions that must be observed for this intended application.

Hypercomplex OFDM schemes for cross-polarized antennas

This paper presents orthogonal frequency-division multiplexing (OFDM) schemes for wireless communications using quaternions and hypercomplex commutative algebras. Although there is no simple or common definition for hypercomplex Fourier transform, it is shown that the 1-D function quaternion Fourier transform is well appropriated for the OFDM schemes. This 1-D function transform also applies with success for the hypercomplex commutative algebras. The important quaternion shift property necessary in OFDM as guard interval to combat ISI also applies appropriately to these schemes. Transmitter and receiver schemes were simulated using MIMO wireless links by means of cross-polarized antennas. Quaternion simulations suggest that the performance of the modulation schemes, concerning the bit error rate versus Eb/N0, is independent of the Fourier transform axis for narrowband and orthogonal channels. For non flat fading or non orthogonal channels, the Cayley-Dicksons composition form must be taken in consideration. Another new interesting result shown at this paper is the performance equivalence of the quaternion OFDM with the hypercomplex commutative algebras OFDM.

Analysis of the implementation of hybrid functions in the current brazilian digital television system

Currently, interactivity has a fundamental role in DTV systems. With the arrival of smart-phones, tablets, and other gadgets connected to Internet, advanced DTV functions are required for this new scenario. Worldwide hybrid television standards are being developed looking to bring interactivity to any electronic device of integrating the broadcast television signal and the broadband network. This offer a myriad of possibilities for interactive applications that will be able to target people of all ages, sex, physical, social or cultural condition. This paper makes a study about implementation of hybrid digital TV functions in the ISDB-T, taking as reference the HbbTV standardization, as well as the potential impact on users and stakeholders.

Desenvolvimento de Aplicações Educacionais para Televisão Digital: Proposta de Mídias em Flash

Este artigo apresenta uma ferramenta desimulacao do modulador ISDB-TB, que permite realizaranalises complexas em cada estagio de processamento. Apartir de um arquivo Broadcast Transport Stream (BTS) epossivel acompanhar o processamento realizado em cadabloco do modulador ate o estagio final de transmissao.Utilizando um gerador de sinal vetorial e possivel realizartransmissoes reais com os arquivos de RF gerados nosimulador. Uma abordagem matematica e pratica sobre ofuncionamento de cada bloco que constitui o modulador erealizada iniciando pela descricao do sinal BTS ate oestagio final de transmissao.This article will explain some of the general ideas and specific techniques for usingambience in live broadcast audio that the author has developed over the past 30 years in thetelevision industry. The paper is concerned with stereo sound fields. The use of ambiencein a surround matrix is similar in approach, though it of course involves the perspective offront/back in addition to left/right.Este artigo apresenta medidas praticas da area de cobertura de uma emissora de televisao digital experimental da empresa Linear Equipamentos Eletronicos, operando em rede de frequencia unica (Single Frequency Network - SFN) na cidade de Santa Rita do Sapucai, Minas Gerais. O trabalho aborda aspectos teoricos de multiplos sinais resguardados por um prefixo ciclico, a utilizacao de distribuicao de conteudo por satelite, o emprego de enlaces terrestres na faixa de microondas para distribuicao de BTS e as particularidades em se empregar moduladores de diferentes fabricantes.Os receptores de TV Digital terrestre possuem umsoftware de sistema operacional que eventualmente necessita seratualizado pelo fabricante. Alem dos metodos tradicionais viaporta USB, internet, ou atraves das redes de servicos autorizados,surge a possibilidade desta atualizacao ser realizada pelo aratraves do proprio sinal digital que esta sendo recebido, sem anecessidade de intervencao do usuario. O sistema japones de TVDigital, onde o sistema brasileiro esta baseado tambem para aatualizacao de receptores via ar, possui uma entidadecentralizadora que e responsavel por controlar o conteudo detodos os fabricantes e envia-los aos receptores. No Brasil, por naoexistir tal entidade, criou-se um modelo de transmissao onde epossivel que cada emissora seja capaz de gerenciar seu proprioconteudo de download e envia-lo de acordo com o especificadopor cada fabricante. Este trabalho apresenta o estudo realizado,juntamente com o grupo de pesquisas da norma ABNT NBR15603 e os fabricantes de receptores, com a finalidade de definir aestrutura necessaria para cada radiodifusor, de forma a permitirque o envio de dados seja feito de maneira descentralizada e semque haja perdas para o usuario final.Este trabalho pretende continuar a discussao, em nivel teorico, desenvolvida no Congresso Set 2007, sobre o planejamento da grade de programacao em Televisao Digital Interativa. No atual cenario, os emissores tem o desafio de adequar as multiplas possibilidades de producao e distribuicao de conteudo da mais alta tecnologia, para um publico de cultura heterogenea e de contrastes sociais marcantes. Com a digitalizacao, a midia se transforma para alem da experiencia de assistir a uma programacao sequencial e se torna pervasiva, favorecendo, inclusive, o uso de recursos interativos em ambientes moveis e portateis. A televisao, enfim, adquire o status tecnologico que possibilita sua definitiva integracao ao ciberespaco, levando consigo, pela usabilidade, pelo entretenimento e pelo sentido de comunhao, a parcela da populacao que o computador, sozinho, nao alcanca. Contudo, a questao mais relevante, no processo de convergencia, esta na constituicao de uma grade que mantenha seu foco nas experiencias genuinamente televisivas. Aquelas que estimulam a interacao social, do publico entre si e com o assunto em pauta. O HDTV aumenta o prazer compartilhado de assistir televisao em casa. Os dispositivos moveis sao digitais e seus usuarios, interativos. Nesse cenario, tem muito a ganhar a programacao que souber conciliar a liberdade individual de escolhas com a satisfacao da experiencia comum, que primeiro estabelecer seus paradigmas “televisivos” de interacao com o publico.Com o advento do Sistema Brasileiro de TV Digital (SBTVD), e tendo em conta osseus recursos de universalizacao previstos no cronograma de implantacao, umagrande variedade de tecnologias de displays (incluindo receptores de altaresolucao, displays de celulares, etc.) ira requerer ensaios de resposta e defidedignidade colorimetrica para a adequada insercao no mercado brasileiro.Neste contexto, e importante destacar que a qualidade da resposta cromatica, naotica do telespectador, depende nao somente da adequacao dos parâmetros doSistema transmissor, mas tambem do desempenho dos displays (modernosdisplays planos ou Flat Panel Displays -FPD), dos efeitos de distorcoes em corproduzidas por nao linearidades nos set-top box e outros dispositivos detratamento de sinal de video.De uma maneira geral, a questao da fidelidade da resposta cromatica de displaysextrapola questoes ou elementos de apreciacao puramente subjetiva (qualidadeda resposta de um receptor de TV), assumindo cada vez mais relevância nomundo moderno a associacao das coordenadas de cor do elemento cromatico dodisplay a um dado mensurando: na area da saude, as cores apresentadas nosdisplays estao relacionadas a diagnosticos; no campo da ciencia, o espectrocromatico esta associado, cada vez de forma mais ampla, a novos mensurandos(altitude, temperatura, pressao, vazao, tipo de vegetacao, caracteristicasgeologicas, etc.).O objetivo deste trabalho e apresentar os testes a serem adotadas pelo CPqD eDIOPT/Inmetro no sentido de efetuar a caracterizacao de FPDs, em conformidadecom normas e recomendacoes internacionais e cadeias de rastreabilidadeenvolvidas.Este artigo apresenta um estudo de obras audiovisuais que utilizam a interatividade em sua narrativa, os chamados videos interativos, presentes na web e em DVD. Desenvolve uma discussao sobre as diferencas entre interacao e interatividade em videos interativos. Estabelece uma classificacao em modalidades das formas interativas em audiovisualEste trabalho pretende apresentar uma metodologia para mensuracao das degradacoes sofridas pelo sinal de video quando e transportado por redes IP....

Pulse Shaping Filter Design for Filtered OFDM Transceivers

CP-OFDM waveforms have been used successfully in the physical layer of 4G systems to overcome the channel selectivity and to provide good spectrum efficiency and high transmission data rates. 5G technology aims to support more communication services than its predecessor and considers many other scenarios such as the use of fragmented spectrum. However, this diversity of services cannot be supported by CP-OFDM since it applies a single set of parameters to the entire band to meet a particular service and it has large out-of-band spectral emission, which can affect transmissions in adjacent bands. Thus, in order to improve the spectrum containment, new waveforms more flexible than CP-OFDM have been proposed which make use of pulse shape filters. UFMC is a waveform that splits the bandwidth into several subbands which can be allocated to services with a particular set of parameters each. However, since the maximum length of UFMC filters is limited to size of CP, their stopband attenuation level can be not enough to meet spectrum emission mask requirements. This work presents a filter called semi-equiripple which has variable stopband decay rate, better frequency response than equiripple, and windowed sinc filters and good impulse response characteristics for reduction of ISI. The performance of the proposed filter is assessed in terms of the power spectrum density, spectrum mask compliance, MER, and operation in a multiservice asynchronous scenario.