Free Space Optical (FSO) satellite communications is proving to be a key enabling technology for global connectivity with the ability to provide connection across Europe with only 12 ground stations. For this, Deutsches Zentrum für Luft- und Raumfahrt (DLR) is working on implementing a robust communication system for FSO on a Xilinx RFSoC Field Programmable Gate Array (FPGA)( ZU28DR). However, FSO is susceptible to deep fades and atmospheric turbulence affecting the quality of the communication system. Thus, measuring the performance of the communication system is crucial for choosing system parameters and designing new blocks to enhance the performance. In this thesis, a high speed test-bed implementation exploiting Parallel Pseudo Random Binary Sequence (PRBS) to measure the performance of the system is implemented. The test-bed is designed to mitigate channel fading problems to correctly calculate the Bit Error Rate (BER). The test-bed is designed to allow for online adjustment of the communication system to facilitate parameter optimizations. / FSO-satellitkommunikation visar sig vara en viktig teknologi för global anslutning med förmågan att tillhandahålla anslutning över Europa med endast 12 markstationer. För detta arbetar DLR med att implementera ett robust kommunikationssystem för FSO på en Xilinx RFSoC FPGA (ZU28DR). Men FSO är känsligt för djupa fades och atmosfärisk turbulens som påverkar kvaliteten på kommunikationssystemet. Därför är mätningen av systemets prestanda avgörande för att välja systemparametrar och designa nya block för att förbättra prestanda. I denna avhandling implementeras en höghastighets testbädd som utnyttjar parallel PRBS för att mäta systemets prestanda. Testbädden är designad för att motverka kanalförlustproblem för att korrekt beräkna BER. Testbädden är designad för att tillåta justering av kommunikationssystemet online för att underlätta optimering av parametrar

<p>Free-space optical (FSO) communication is a potential technology for last-mile applications. Key advantages are the unlicensed spectrum, high transmission rates, and inherent security. Moreover, Radio-over-FSO (RoFSO) allows seamless integration between the incompatible radio frequency (RF) and optical networks. Such advantages qualify FSO systems to take a front seat in next-generation broadband communication networks. However, the main challenge for FSO systems is the performance degradation imposed by the atmospheric attenuation and turbulence. To exploit the advantages of FSO systems, accurate and computationally-efficient channel models are required. This thesis represents in-field experimental work related to FSO channel measurement as well as the transmission of orthogonal frequency division multiplexing (OFDM) over the FSO channel. A 1.87-km FSO link installed at McMaster University is employed. A high-speed field-programmable gate array (FPGA)-based digitizer board is used as the underlying hardware platform for interface with the link. A system-on-three-FPGAs is implemented to act as a universal transceiver for signals composed using MATLAB. A new technique is developed for conducting the FSO channel measurement. An optical signal intensity-modulated by a high frequency sinusoid is transmitted. The received signal undergoes a fast-Fourier transform (FFT) to filter out a large portion of the interfering noise providing more accurate measurements. Fitting with the log-normal distribution is investigated. A finite-state Markov model is also derived and its accuracy is verified by the simulation results. The first realization of an in-field OFDM over FSO transmission system is implemented and tested over the link. The received signal is investigated on the symbol level and constellation diagrams are visualized. Transmission rates up to 300 Mbps are achieved with average symbol-error rate (SER) on the order of 10^-6.</p> / Master of Applied Science (MASc)

Les systèmes de communication FSO sont des candidats potentiels pour de solutions de transmission spatiale à large bande. C’est pourquoi la présente thèse s’inscrit dans une contribution d’une nouvelle architecture de réseau FSO dans le cas d’une liaison de communication entre un satellite géostationnaire et une station terrienne. Elle traite aussi de l’influence de l’angle zénithal sur la qualité de la liaison optique en raison de la variation de la scintillation due à la complexité de l’atmosphère. Nous avons établi un nouveau canal de communication tenant compte de la subdivision de l’atmosphère en deux grandes zones de turbulence. Pour améliorer la performance de la liaison, nous avons d’abord placé un relais AF optiques ente le satellite et la station terrienne, ensuite nous avons introduit un paramètre construit `a partir de valeurs : p et 1-p. Le paramètre p correspond au ratio de la distance entre la station terrienne et le relais sur la distance de 36 000 Km correspondant a` l’orbite GEO. Dans notre cas, le relais est placé a 1000 Km a l’exosphère, le paramètre p = 1/36 et enfin la technique de diversité spatiale est appliquée en réception. Les résultats de simulation ont confirmé que les architectures des systèmes proposés sont meilleures que les performances de liaisons optiques directes. / Free space optical systems are potential candidates of large band spatial transmission solutions. In this thesis, FSO network architecture in the case of geo- stationary satellite to earth communication link is investigated and the influence of zenith angle on the quality of the link has been evaluated. Because of the variation of scintillation due to the complexity of the atmosphere, the optical space to earth communication link channel model has been developped. In order to overcome the main limitations of the prop- agation, optical relays with low earth orbit satellites and spatial diversity on earth could improve the link performance. To improve the link performance, an aggregated simulation model turbulence has been built based on parameters ”p” and ”1-p” introduced in the combined model a↵ecting the considered channels. The parameter ” p ” corresponds to the ratio of the distance from the earth to the relay over the total distance of 36 000Km. In the case of 1000 Km for a relay in the exosphere, p = 1/36. Simulation results show that the proposed network system architecture has outperformed the direct link performance

Esta dissertação de mestrado tem por objetivo apresentar, analisar e discutir a experiência de ensino de Francês Língua Estrangeira para estudantes da Escola Politécnica da USP, por meio do Programa CFI (Curso de Francês para Iniciantes). Tal formação, iniciada em 2001, foi concebida pelo Centro de Línguas da Faculdade de Filosofia, Letras e Ciências Humanas da Universidade de São Paulo a pedido da Comissão de Relações Internacionais da Escola Politécnica, e tinha por finalidade preparar os alunos que fossem fazer dois anos de curso em faculdades de engenharia francesas (Ecoles Polytechniques, Ecoles Centrales, Ponts et Chaussés, etc), no âmbito do Programa Duplo Diploma em Engenharia promovida pela Poli-USP. Nosso estudo corresponde ao período em que se decidiu discutir a progressão e o equilíbrio entre as duas modalidades de ensino trabalhadas - o Francês, Língua Estrangeira (FLE) geral e o Francês com Objetivos Específicos (FOS) - na formação dos estudantes, que passara de 2 para 3 anos, incluindo um módulo específico (Módulo France) e cujo número de inscritos havia chegado a quinhentos por semestre letivo. Nesse período, coube à equipe pedagógica a concepção geral do curso e a preparação do material didático de cada um dos seis módulos de ensino oferecidos, o que trouxe resultados bastante positivos, como mostram os questionários respondidos por alunos do Duplo Diploma que participaram de tal formação. / The objective of this undergraduate thesis is to present, analyze and discuss the experience of teaching French as a foreign language for students at the Polytechnic School at University of São Paulo through the FCB Program (French Course for Beginners). This course, started in 2001, was designed by the Language Center at the College of Philosophy, Languages and Human Sciences of the University of São Paulo by request of the International Relations Commission of the Polytechnic School to prepare students who had been selected for the Dual Diploma Program in Engineering sponsored by Poli-USP, that is, a program in which students would spend two years of their undergraduate program at a French College of Engineering (Ecoles Polytechniques, Ecoles Centrales, Ponts et Chaussés, etc). Our study corresponds to the period in which we decided to reevaluate the progress and the balance between the two approaches used during the course general French as a Foreign Language (FFL) and French with Specific Objectives (FSO) a course which had increased from 2 to 3 years and which included a specific module (France module) and whose number of enrolled participants had reached 500 per semester. During this period, the pedagogical team (coordinators and teachers) were responsible for the general conception of the new course and for the textbooks of each one of the 6 teaching modules offered. The results obtained were extremely satisfactory as shown in the questionnaires answered by the Dual Diploma students who took this course.

Esta dissertação de mestrado tem por objetivo apresentar, analisar e discutir a experiência de ensino de Francês Língua Estrangeira para estudantes da Escola Politécnica da USP, por meio do Programa CFI (Curso de Francês para Iniciantes). Tal formação, iniciada em 2001, foi concebida pelo Centro de Línguas da Faculdade de Filosofia, Letras e Ciências Humanas da Universidade de São Paulo a pedido da Comissão de Relações Internacionais da Escola Politécnica, e tinha por finalidade preparar os alunos que fossem fazer dois anos de curso em faculdades de engenharia francesas (Ecoles Polytechniques, Ecoles Centrales, Ponts et Chaussés, etc), no âmbito do Programa Duplo Diploma em Engenharia promovida pela Poli-USP. Nosso estudo corresponde ao período em que se decidiu discutir a progressão e o equilíbrio entre as duas modalidades de ensino trabalhadas - o Francês, Língua Estrangeira (FLE) geral e o Francês com Objetivos Específicos (FOS) - na formação dos estudantes, que passara de 2 para 3 anos, incluindo um módulo específico (Módulo France) e cujo número de inscritos havia chegado a quinhentos por semestre letivo. Nesse período, coube à equipe pedagógica a concepção geral do curso e a preparação do material didático de cada um dos seis módulos de ensino oferecidos, o que trouxe resultados bastante positivos, como mostram os questionários respondidos por alunos do Duplo Diploma que participaram de tal formação. / The objective of this undergraduate thesis is to present, analyze and discuss the experience of teaching French as a foreign language for students at the Polytechnic School at University of São Paulo through the FCB Program (French Course for Beginners). This course, started in 2001, was designed by the Language Center at the College of Philosophy, Languages and Human Sciences of the University of São Paulo by request of the International Relations Commission of the Polytechnic School to prepare students who had been selected for the Dual Diploma Program in Engineering sponsored by Poli-USP, that is, a program in which students would spend two years of their undergraduate program at a French College of Engineering (Ecoles Polytechniques, Ecoles Centrales, Ponts et Chaussés, etc). Our study corresponds to the period in which we decided to reevaluate the progress and the balance between the two approaches used during the course general French as a Foreign Language (FFL) and French with Specific Objectives (FSO) a course which had increased from 2 to 3 years and which included a specific module (France module) and whose number of enrolled participants had reached 500 per semester. During this period, the pedagogical team (coordinators and teachers) were responsible for the general conception of the new course and for the textbooks of each one of the 6 teaching modules offered. The results obtained were extremely satisfactory as shown in the questionnaires answered by the Dual Diploma students who took this course.

The exponential increase in the number of mobile users, coupled with the strong demand for high-speed data services results in a significant growth in the required cellular backhaul capacity. Optimizing the cost efficiency while increasing the capacity is becoming a key challenge to the cellular backhaul. It refers to connections between base stations and mobile switching nodes over a variety of transport technologies such as copper, optical fibers, and radio links. These traditional transmission technologies are either expensive, or cannot provide high data rates. This work is focused on the opportunities of free-space-optical (FSO) technology in next generation cellular back- haul. FSO is a cost effective and wide bandwidth solution as compared with the traditional radio-frequency (RF) transmission. Moreover, due to its ease of deployment, license-free operation, high transmission security, and insensitivity to interference, FSO links are becoming an attractive solution for next generation cellular networks. However, the widespread deployment of FSO links is hampered by the atmospheric turbulence-induced fading, weather conditions, and pointing errors. Increasing the reliability of FSO systems, while still exploiting their high data rate communications, is a key requirement in the deployment of an FSO-based backhaul. Therefore, the aim of this work is to provide different approaches to address these technical challenges. In this context, investigation of hybrid automatic repeat request (HARQ) protocols from an information-theoretic perspective is undertaken. Moreover, performance analysis of asymmetric RF/FSO dual-hop systems is studied. In such system models, multiple RF users can be multiplexed and sent over the FSO link. More specifically, the end-to-end performance metrics are presented in closed-form. This also has increased the interest to study the performance of dual-hop mixed FSO/RF systems, where the FSO link is used as a multicast channel that serves different RF users. Having such interesting results motivates further the analysis of dual-hop FSO fixed-gain relaying communication systems, and exact closed-form performance metrics are presented in terms of the bivariate H-Fox function. This model is further enhanced through the deployment of a multihop FSO relaying system as an efficient technique to mitigate the turbulence-induced fading as well as pointing errors.

The submitted work deals with issues of optical transmissions and its security. We will become familiar with a variety of transferability of information, based on which we can assess the advantages and disadvantages of each technology as compared to optical information transmission. Based on acquired information we will try to implement interception of optical communication of cable TV provider.

Tato diplomová práce pojednává o zmírnění bitové chybovosti bezkabelového optického spoje s užitím principu reciprocity aplikovaného na komunikační kanál, spolu s možností kódování přenášených dat. V této práci je implementováno LDPC a Reed-Solomonovo kódování pro jejich vyhovující vlastnosti. Zbytková rámcová chybovost je vypočtena a k dispozici jako výstup systému, který je implementovaný v hradlovém poli (FPGA).

Generalized fading has been an imminent part and parcel of wireless communications. It not only characterizes the wireless channel appropriately but also allows its utilization for further performance analysis of various types of wireless communication systems. Under the umbrella of generalized fading channels, a unified performance analysis of a free-space optical (FSO) link over the Malaga (M) atmospheric turbulence channel that accounts for pointing errors and both types of detection techniques (i.e. indirect modulation/direct detection (IM/DD) as well as heterodyne detection) is presented. Specifically, unified exact closed-form expressions for the probability density function (PDF), the cumulative distribution function (CDF), the moment generating function (MGF), and the moments of the end-to-end signal-to-noise ratio (SNR) of a single link FSO transmission system are presented, all in terms of the Meijer's G function except for the moments that is in terms of simple elementary functions. Then capitalizing on these unified results, unified exact closed-form expressions for various performance metrics of FSO link transmission systems are offered, such as, the outage probability (OP), the higher-order amount of fading (AF), the average error rate for binary and M-ary modulation schemes, and the ergodic capacity (except for IM/DD technique, where closed-form lower bound results are presented), all in terms of Meijer's G functions except for the higher-order AF that is in terms of simple elementary functions. Additionally, the asymptotic results are derived for all the expressions derived earlier in terms of the Meijer's G function in the high SNR regime in terms of simple elementary functions via an asymptotic expansion of the Meijer's G function. Furthermore, new asymptotic expressions for the ergodic capacity in the low as well as high SNR regimes are derived in terms of simple elementary functions via utilizing moments. All the presented results are verified via computer-based Monte-Carlo simulations. Besides addressing the pointing errors with zero boresight effects as has been addressed above, a unified capacity analysis of a FSO link that accounts for nonzero boresight pointing errors and both types of detection techniques (i.e. heterodyne detection as well as IM/DD) is also addressed. Specifically, an exact closed-form expression for the moments of the end-to-end SNR of a single link FSO transmission system is presented in terms of well-known elementary functions. Capitalizing on these new moments expressions, approximate and simple closed-form results for the ergodic capacity at high and low SNR regimes are derived for lognormal (LN), Rician-LN (RLN), and M atmospheric turbulences. All the presented results are verified via computer-based Monte-Carlo simulations. Based on the fact that FSO links are cost-effective, license-free, and can provide even higher bandwidths compared to the traditional radio-frequency (RF) links, the performance analysis of a dual-hop relay system composed of asymmetric RF and FSO links is presented. This is complemented by the performance analysis of a dual-branch transmission system composed of a direct RF link and a dual-hop relay composed of asymmetric RF and FSO links. The performance of the later scenario is evaluated under the assumption of the selection combining (SC) diversity and the maximal ratio combining (MRC) schemes. RF links are modeled by Rayleigh fading distribution whereas the FSO link is modeled by a unified GG fading distribution. More specifically, in this work, new exact closed-form expressions for the PDF, the CDF, the MGF, and the moments of the end-to-end SNR are derived. Capitalizing on these results, new exact closed-form expressions for the OP, the higher-order AF, the average error rate for binary and M-ary modulation schemes, and the ergodic capacity are offered. Cognitive radio networks (CRN) have also proved to improve the performance of wireless communication systems and hence based on this, the hybrid system analyzed above is extended with CRN technology wherein the outage and error performance analysis of a dual-hop transmission system composed of asymmetric RF channel cascaded with a FSO link is presented. For the RF link, an underlay cognitive network is considered where the secondary users share the spectrum with licensed primary users. Indoor femtocells act as a practical example for such networks. Specifically, it is assumed that the RF link applies power control to maintain the interference at the primary network below a predetermined threshold. While the RF channel is modeled by the Rayleigh fading distribution, the FSO link is modeled by a unified Gamma-Gamma turbulence distribution. The FSO link accounts for pointing errors and both types of detection techniques (i.e. heterodyne detection as well as IM/DD). With this model, a new exact closed-form expression is derived for the OP and the error rate of the end-to-end SNR of these systems in terms of the Meijer's G function and the Fox's H functions under amplify-and-forward relay schemes. All new analytical results are verified via computer-based Monte-Carlo simulations and are illustrated by some selected numerical results.

This thesis comprises of two parts. In the first, we improve the performance of existing hybrid FSO/RF communication systems. Conventional hybrid RF and optical wireless communication systems make use of independent and parallel Free Space Optical (FSO) and RF channels to achieve higher reliability than individual channels. This thesis is based on the idea that true hybridization can be accomplished only when both channels collaboratively compensate the shortcomings of each other and thereby, improve the performance of the system as a whole. We believe that optimization on the combined channel capacities instead of the individual channel capacities of the FSO and RF channels can increase the system availability by a large amount. Using analysis and simulation, we show that, by using Hybrid Channel Codes, we can obtain more than two orders of magnitude improvement in bit error rates and many-fold increase in system availability over the currently existing best systems. Simulations also show that the average throughput obtained using the new system is over 35% better when compared to the present systems. The goodput is much higher because of the elimination of data repetition. Also by avoiding data duplication, we preserve to a great extent the crucial security benefits of FSO communications. The second half of the thesis deals with magnetic recording systems. Due to the insatiable and ever-increasing needs of data storage, novel techniques have to be developed to improve the capacity of magnetic recording channels. These capacity requirements translate to improving storage densities and using higher recording rates. For these channels, improvements even in the order of a tenths of a dB have a big impact on the storage densities of the recording device. Recently, LDPC codes have been constructed to achieve the independent and uniformly distributed (i.u.d.) capacity of partial response (PR) channels. The “guess algorithm” has been proposed for memoryless channels, to improve the performance of iterative belief propagation decoding to that of Maximum Likelihood (ML) decoding. In the second part of this thesis, the “guess algorithm” is extended to channels with memory. It is shown using asymptotic density evolution analysis that the gains obtained using this algorithm on these channels are more than those obtained over memoryless channels. The “guess algorithm” is further extended to magnetic recording channels which are characterized by ISI and additive white gaussian noise (AWGN). Simulations show that gains of upto one dB are possible on magnetic recording channels.