Στα πλαίσια της συγκεκριμένης μεταπτυχιακής εργασίας εξετάζονται διάφορες τεχνικές βελτίωσης των modems που χρησιμοποιούνται στους δέκτες των xDSL συστημάτων, προκειμένου να επιτευχθεί μεγιστοποίηση της ταχύτητας μετάδοσης. Τα xDSL συστήματα είναι συστήματα που χρησιμοποιούν διαμόρφωση πολλαπλών φερουσών (Discrete Multitone – DMT). Η συμβατική μορφή ισοστάθμισης που απαντάται στα συστήματα αυτά, αποτελείται από έναν ισοσταθμιστή Τ-συντελεστών (Τ-tap) που ενεργεί στο πεδίο του χρόνου (TEQ) ακολουθούμενο από Ν ισοσταθμιστές 1-tap που δρουν στο πεδίο της συχνότητας (FEQ) σε κάθε τόνο ξεχωριστά. Η πρόταση που εξετάζεται σε αυτή τη διπλωματική εργασία είναι η μεταφορά του ισοσταθμιστή από το πεδίο του χρόνου στο πεδίο της συχνότητας και ο κατάλληλος συνδυασμός του με τον FEQ. Επομένως, θα προκύψει ένα σύστημα που θα αποτελείται από Ν παράλληλους ισοσταθμιστές T-tap ο κάθε ένας από τους οποίους θα λειτουργεί σε κάθε τόνο ξεχωριστά (Ισοστάθμιση ανά τόνο – PTEQ) . Με τον τρόπο αυτό επιτυγχάνεται η μεγιστοποίηση του ρυθμού μετάδοσης και ελαττώνεται η ευαισθησία του δέκτη στις παραμέτρους του καναλιού. Τα δύο προαναφερθέντα μοντέλα ισοστάθμισης, ο βέλτιστος PTEQ (MMSE PTEQ) και ο συνδυασμός ΤΕQ/FEQ συγκρίνονται μεταξύ τους. Ο βέλτιστος PTEQ παρουσιάζει μεγάλη πολυπλοκότητα κατά τον υπολογισμό των συντελεστών του. Για να γίνει αποδοτικά η αξιοποίηση των θετικών του στοιχείων, εξετάζονται διάφοροι προσαρμοστικοί τρόποι υπολογισμού του, με χρήση των αλγορίθμων RLS και LMS κατάλληλα ενταγμένων στο MMSE σύστημα. / This postgraduate thesis is about improvement techniques for modems which are used at the xDSL systems’ receivers, in order to maximize bit rate. xDSL systems are using multiple carrier modulation (Discrete Multitone – DMT). The conventional equalization scheme for these systems consists of one T-taps time domain equalizer (TEQ) followed by N 1-tap frequency domain equalizers (FEQ) per tone. In this thesis is proposed a modified scheme where the time domain equalizer is replaced by a frequency domain one, properly combined with the 1-tap FEQs. The resulting structure consists of N T-taps frequency domain equalizers per tone (Per Tone Equalizer – PTEQ). The outcome is a larger bit rate while the per tone receiver has reduced sensitivity to the channel’s parameters. The aforesaid equalization models, the optimal PTEQ (MMSE PTEQ) and the combined TEQ/FEQ, are compared. The optimal PTEQ structure presents great complexity during the calculation of its coefficients. In order to efficiently exploit its advantages, adaptive methods, using RLS and LMS algorithms properly imported at the MMSE system, are examined.

We study and analyze the performance of iterative equalization and decoding (IED) using an M-BCJR equalizer. We use bit error rate (BER), frame error rate simulations and extrinsic information transfer (EXIT) charts to study and compare the performances of M-BCJR and BCJR equalizers on precoded and non-precoded channels. Using EXIT charts, the achievable channel capacities with IED using the BCJR, M-BCJR and MMSE LE equalizers are also compared. We predict the BER performance of IED using the M-BCJR equalizer from EXIT charts and explain the discrepancy between the observed and predicted performances by showing that the extrinsic outputs of the $M$-BCJR algorithm are not true logarithmic-likelihood ratios (LLR's). We show that the true LLR's can be estimated if the conditional distributions of the extrinsic outputs are known and finally we design a practical estimator for computing the true LLR's from the extrinsic outputs of the M-BCJR equalizer.

Transmission of digital information through a wireless channel with resolvable multipaths or a bandwidth limited channel results in intersymbol interference (1SI) among a number of adjacent symbols. The design of an equalizer is thus important to combat the ISI problem for these types of channels and hence provides reliable communication. Channel coding is used to provide reliable data transmission by adding controlled redundancy to the data. Turbo equalization (TE) is the joint design of channel coding and equalization to approach the achievable uniform input information rate of an ISI channel. The main focus of this dissertation is to investigate the different TE techniques used for a static frequency selective additive white Gaussian noise (AWGN) channel. The extrinsic information transfer (EXIT) chart is used to analyse the iterative equalization/decoding process and to determine the minimum signal to noise ratio (SNR) in order to achieve convergence. The use of the Minimum Mean Square Error (MMSE) Linear Equalizer (LE) using a priori information has been shown to achieve the same performance compared with the optimal trellis based Maximum A Posterior (MAP) equalizer for long block lengths. Motivated by improving the performance of the MMSE LE, two equalization schemes are initially proposed: the MMSE Linear Equalizer with Extrinsic information Feedback (LE-EF (1) and (U)). A general structure for the MMSE LE, MMSE Decision Feedback Equalizer (DFE) and two MMSE LE-EF receivers, using a priori information is also presented. The EXIT chart is used to analyse the two proposed equalizers and their characteristics are compared to the existing MAP equalizer, MMSE LE and MMSE DFE. It is shown that the proposed MMSE LE-EF (1) does have an improved performance compared with the existing MMSE LE and approaches the MMSE Linear Equalizer with Perfect Extrinsic information Feedback (LE-PEF) only after a large number of iterations. For this reason the MMSE LE-EF is shown to suffer from the error propagation problem during the early iterations. A novel way to reduce the error propagation problem is proposed to further improve the performance of the MMSE LE-EF (I). The MAP equalizer was shown to offer a much improved performance over the MMSE equalizers, especially during the initial iterations. Motivated by using the good quality of the MAP equalizer during the early iterations and the hybrid MAP/MMSE LE-EF (l) is proposed in order to suppress the error propagation problem inherent in the MMSE LE-EF (I). The EXIT chart analysis reveals that the hybrid MAP/MMSE LE-EF (l) requires fewer iterations in order to achieve convergence relative to the MMSE LE-EF (l). Simulation results demonstrate that the hybrid MAP/MMSE LE-EF (I) has a superior performance compared to the MMSE LE-EF (I) as well as approaches the performance of both the MAP equalizer and MMSE LE-PEF at high SNRs, at the cost of increased complexity relative to the MMSE LEEF (I) receiver. The final part of this dissertation considers the use of precoders in a TE system. It was shown in the literature that a precoder drastically improves the system performance. Motivated by this, the EXIT chart is used to analyse the characteristics of four different precoders for long block lengths. It was shown that using a precoder results in a loss in mutual information during the initial equalization stage. However" we show by analysis and simulations that this phenomenon is not observed in the equalization of all precoded channels. The slope of the transfer function, relating to the MAP equalization of a precoded ISI channel (MEP), during the high input mutual information values is shown to play an important role in determining the convergence of precoded TE systems. Simulation results are presented to show how the precoders' weight affects the convergence of TE systems. The design of the hybrid MAP/MEP equalizer is also proposed. We also show that the EXIT chart can be used to compute the trellis code capacity of a precoded ISI channel. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2003.

Thesis(M.S.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references (p.51-53).

Thesis (Ph.D.) - Carleton University, 2005. / Includes bibliographical references (p. 200-213). Also available in electronic format on the Internet.

Thesis (M.App.Sc.) - Carleton University, 2007. / Includes bibliographical references (p. 90-92). Also available in electronic format on the Internet.

Thesis (M.S.)--Rochester Institute of Technology, 2005. / Typescript. Includes bibliographical references (leaves 70-72).

Η παρούσα ειδική ερευνητική εργασία εκπονήθηκε στα πλαίσια του Διατμηματικού Προγράμματος Μεταπτυχιακών Σπουδών στην “Ηλεκτρονική και Επεξεργασία της Πληροφορίας” στο τμήμα Φυσικής του Πανεπιστήμιου Πατρών. Ο στόχος της παρούσας εργασίας είναι η δημιουργία ενός αναπτυξιακού συστήματος για την υλοποίηση εφαρμογών που απαιτούν τη χρήση του δικτύου κινητής τηλεφωνίας. Το σύστημα αυτό θα πρέπει να μπορεί να λειτουργήσει αυτόνομα χωρίς υποστήριξη υπολογιστή. Το σύστημα έχει τη δυνατότητα χρήσης του δικτύου κινητής τηλεφωνίας (φωνή και δεδομένα) μέσω της χρήσης GSM Modem. Η αλληλεπίδραση με τον χρήστη γίνεται μέσω έγχρωμης οθόνης αφής με ενσωματωμένο resistive touch controller, που συμβάλει στην αυτόνομη λειτουργία του συστήματος. Το DSK 6713, που ενσωματώνει το TMS320C6713 DSP χρονίζεται στα 225 MHz, χρησιμοποιείται σαν κεντρική μονάδα για τη διασύνδεση αυτών αλλά και για την ανάπτυξη της όποιας εφαρμογής. Στο DSP υπάρχει διασυνδεδεμένος Audio Codec, μνήμη RAM και DMA Controller. To DSK C6713 δίνει τη δυνατότητα μέσω θυρών που έχει διαθέσιμες για την διασύνδεση και άλλων εξωτερικών συσκευών όπως κάμερα και SD card. Μαζί με το σύστημα αναπτύχθηκε και κώδικας για την επικοινωνία των υποσυστημάτων, καθώς και μία εφαρμογή γραφικού ισοσταθμιστή που κάνει χρήση δυνατοτήτων του συστήματος για την επίδειξη ορθής λειτουργίας αυτού. Το πρώτο κεφάλαιο αναφέρεται στην διασύνδεση των υποσυστημάτων και στους περιορισμούς που υπήρχαν από την κάθε πλευρά. Στο δεύτερο κεφάλαιο περιγράφονται τα υποσυστήματα που αποτελούν το αναπτυξιακό. Στο τρίτο κεφάλαιο αναλύεται η εφαρμογή που αναπτύχθηκε στην κεντρική μονάδα, ενώ στο τέταρτο κεφάλαιο το τμήμα της εφαρμογής που αναπτύχθηκε στην οθόνη αφής. Τέλος στο τελευταίο κεφάλαιο παρουσιάζονται τα αποτελέσματα της εφαρμογής που υλοποιήθηκε . / This special research work was performed in the frame of the requirements of the M.Sc. "Electronics & Computers" in the Department of Physics at the University of Patras. The purpose of this study is to create a development system for developing applications that require the use of the mobile network. This system should be able to work independently without computer support. The system has the ability to use the mobile network (voice and data) by using GSM Modem. The user interaction is via color touch screen with an integrated resistive touch controller, which contributes to the autonomous system operation. The DSK C6713, which incorporates the TMS320C6713 DSP, that is clocked at 225 MHz, is used as a central unit for interconnecting these and for the development of any application. The DSP is interconnected with an Audio Codec, a RAM Memory and a DMA Controller. The DSK C6713 enables interconnection with other external devices such as camera and SD card. In addition, a code was developed for the communication of the subsystems. An application of a graphic equalizer was developed too, in order to make use of the system capabilities to demonstrate proper operation of this. The first chapter deals with the interconnection of the subsystems and the restrictions that existed on each side. The second chapter describes the subsystems that constitute the development. In the third chapter is described the application developed in the central unit while the fourth chapter presents the section of the application that was developed on the touch screen. Finally the last chapter presents the results of the application that were implemented.

Orientador: João Marcos Travassos Romano, Ricardo Suyama / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-14T00:41:40Z (GMT). No. of bitstreams: 1 Costa_MicheleNazarethda_M.pdf: 1765125 bytes, checksum: ca7881285ef04b9d9226595f3dd1e90c (MD5) Previous issue date: 2009 / Resumo: Esta dissertação teve como motivação inicial a busca de uma abordagem unificada para o problema de equalização não-supervisionada, a ser aplicada às configurações SISO, SIMO e MIMO. Tal abordagem se refere a dois aspectos fundamentais do problema: a estrutura do equalizador e a otimização de seus parâmetros. Desta forma, propomos uma mesma metodologia para estudar, nas três configurações citadas, o que denominamos de limitação estrutural e de limitação de critério. A primeira é caracterizada pela impossibilidade de inversão perfeita do canal fazendo uso de apenas filtros com resposta impulsiva finita (FIR); a segunda se refere às limitações quanto ao uso de estatísticas de ordem dois (EO2) para a obtenção do equalizador ótimo no caso não-supervisionado. Para tal análise, reunimos resultados um tanto dispersos na literatura para formalizar de maneira unificada e acessível os conceitos de sistema inversível e de sistema de fase mínima para as três configurações. Em seguida, empregamos o conceito de filtro de erro de predição linear para estudar o uso de EO2 em equalização, estendendo esse conceito também às três configurações / Abstract: This dissertation was motivated by the idea of developing a unified approach to the problem of unsupervised equalization, in the context of SISO, SIMO and MIMO channels. This approach is concerned with two fundamental aspects of the equalization problem: the structure of the equalizer and the optimization of its parameters. In this sense, we propose a same methodology to study, in the three aforementioned scenarios, two different limitations. The first one, which we denote structural limitation, is related to the impossibility of inverting any channel employing only finite impulse response (FIR) filters. The second one, which we call criterion limitation, refers to the limitation regarding the use of second order statistics (SOS) to obtain the equalizer in an unsupervised manner. In order to perform this analysis, we collected results that are rather scattered in the literature to formalize the concepts of invertible and minimum-phase systems in all three scenarios. Then, we use the concept of a prediction-error filter to study the limitation of SOS in the equalization problem / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

Orientador: Bárbara Janet Teruel Mederos / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola / Made available in DSpace on 2018-08-19T15:41:33Z (GMT). No. of bitstreams: 1 Alves_ElaineCangussudeSouza_M.pdf: 1610597 bytes, checksum: 9136ba250ed9462c6fbb4d8204f73a4a (MD5) Previous issue date: 2011 / Resumo: Este trabalho tem como objetivo coletar dados de qualidade de sinal transmitido entre uma estação base e um nó sensor localizado no interior de uma casa de vegetação, localizada no campo experimental da Faculdade de Engenharia Agrícola - UNICAMP, com o auxilio de ferramentas computacionais. No interior da casa de vegetação foi inserido um sistema hidropônico com bancadas que forneciam suporte para morangueiros da cultivar Albion. O conjunto de equipamentos e de nós sensores que foram utilizados para montar a rede é da marca Crossbow®. Após a implantação do nó sensor foram realizados experimentos com o objetivo de verificar alcance e qualidade do sinal de acordo com sua potência. Através desses ensaios foi possível concluir que uma Potência de Sinal com valor de -12,2 dBm seria suficiente para manter a transmissão entre Estação Base e Nó Sensor. Testes também foram realizados para uma Potência de Sinal de -9,2 dBm, e mostraram que a rede possuía qualidade classificada como "muito alta". Porém, através do teste de duração da bateria, nota-se que existe uma economia de energia ao utilizar a Potência de Sinal de -12,2 dBm. No geral, foi demonstrado que o valor da Potência de Sinal tem influência sobre a qualidade do sinal de transmissão e recepção, o gasto de bateria e o alcance do sinal. Assim, este é um importante parâmetro a ser considerado em um projeto de implantação de rede de sensores sem fio no meio agrícola / Abstract: This project aims to collect quality data signals transmitted between a base station and a sensor node located inside a greenhouse, which is a experimental field located in the College of Agricultural Engineering - UNICAMP, with help of computational tools. Inside the greenhouse, a hydroponic system with banks providing support for strawberry Albion was inserted. The set of sensor nodes and equipment that were used to assemble the network is the Crossbow® brand. After sensor node deployment, experiments were performed in order to check range and signal quality. Through these experiments, it was concluded that a RF power value of -12.2 dBm is sufficient to maintain transmissions between base station and the sensor. Tests were also performed to a RF power of -9.2 dBm, and showed that the network had quality rated as "very high". However, by testing the battery life, it is noted that there is an energy saving when the RF power of -12.2 dBm is used. Overall, it was shown that the value of the signal strength has an influence on the quality of signal transmission and reception, battery depletion and signal range. So, this is an important parameter to be considered in a project to establish network of wireless sensors in a agricultural environment / Mestrado / Maquinas Agricolas / Mestre em Engenharia Agrícola