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1
Jimaa, Shibab A. "Data transmission over ADPCM links". Thesis, Loughborough University, 1990. https://dspace.lboro.ac.uk/2134/27385.
Testo completoAbstract (sommario):
The thesis is concerned with serial data transmission at a rate of 9600 bit/sec over a telephone channel containing a 32 kbit/sec Adaptive Differential Pulse Code Modulation (ADPCM) link , which has been proposed by CCITT as an international standard. The transmitted data signal is a 2400 band 16-level Quadrature Amplitude Modulated (QAM) signal. The ADPCM link introduces time-varying and at times severe nonlinear distortion into the data signal.
2
Brine, A. "Direct sequence data transmission systems". Thesis, University of Kent, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379274.
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3
Adama, A. "High performance data transmission filters". Thesis, University of Essex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371923.
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4
Parvez, Imtiaz. "Data Transmission in Quantized Consensus". Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc271874/.
Testo completoAbstract (sommario):
In the world of networked system, average consensus is an important dimension of co-ordinate control and cooperation. Since the communication medium is digital, real value cannot be transmitted and we need to perform quantization before data transmission. But for the quantization, error is introduced in exact value and initial average is lost. Based on this limitation, my 16 bit quantization method (sending MSB in 1-4 cycle and MSB+LSB in 5th cycle) reduces error significantly and preserves initial average. Besides, it works on all types of graphs (star, complete, ring, random geometric graph). My other algorithm, distributing averaging algorithm (PQDA) with probabilistic quantization also works on random geometric graph, star, ring and slow co-herency graph. It shows significant reduced error and attain strict consensus.
5
Johansson, Christian, e Marcus Karlsson. "Characterisation of a data transmission link". Thesis, Linköping University, Department of Science and Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2359.
Testo completoAbstract (sommario):
This report is the result of a Master Thesis work that has been performed between October 2003 and March 2004. The purpose of the work was to evaluate a part of the signal chain in a product of Micronic Laser Systems AB. The evaluation was performed to obtain the characterisation for the signal chain, such as impedances and crosstalk.
The work started with a literature study in order to refresh and increase the knowledge that was needed before the practical work. Then measurements, computer aided simulations and comparisons between these were performed.
Measurements were performed using TDR (Time Domain Reflectometry). The results showed the impedance levels along the signal chain. This was interesting since it showed how well the different parts in the system are matched. Unmatched parts result in reflections that disturb the transmitted signal and contribute to crosstalk, which also was measured.
Simulations were done using ADS (Advance Design System), a tool from Agilent Technologies Inc. A substantial part of the simulation work was to build models of the real system. These models have been used for simulation. The simulation results were then compared to the measurement results.
The results show that the system can be better matched concerning the channel impedance. There are large variations in impedance levels along the signal chain, resulting in signal reflections. Another effect studied is crosstalk between channels. Measurements and simulations showed the presence of crosstalk but it seems to be a minor problem in the current machine.
6
Yilmaz, Ayhan. "Robust Video Transmission Using Data Hiding". Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1093509/index.pdf.
Testo completoAbstract (sommario):
Video transmission over noisy wireless channels leads to errors on video, which
degrades the visual quality notably and makes error concealment an indispensable
job. In the literature, there are several error concealment techniques based on
estimating the lost parts of the video from the available data. Utilization of data
hiding for this problem, which seems to be an alternative of predicting the lost data,
provides a reserve information about the video to the receiver while unchanging the
transmitted bit-stream syntaxhence, improves the reconstruction video quality without significant extra channel utilization. A complete error resilient video transmission codec is proposed, utilizing imperceptible embedded information for combined detecting, resynchronization and reconstruction of the errors and lost data. The data, which is imperceptibly embedded into the video itself at the encoder, is extracted from the video at the decoder side to be utilized in error concealment. A spatial domain error recovery technique, which hides edge orientation information of a block, and a resynchronization technique, which embeds bit length of a block into other blocks are combined, as well as some parity information about the hidden data, to conceal channel errors on intra-coded frames of a video sequence. The errors on inter-coded frames are basically recovered by hiding motion vector information along with a checksum into the next frames. The simulation results show that the proposed approach performs superior to conventional approaches for concealing the errors in binary symmetric channels, especially for higher bit rates and error rates.
7
Tanriover, Cagri C. "Improved turbo codes for data transmission". Thesis, Lancaster University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288960.
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8
Bate, Stephen Donald. "Adaptive coding algorithms for data transmission". Thesis, Coventry University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303388.
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9
Brydon, A. N. "Medium rate data transmission at HF". Thesis, University of Manchester, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506449.
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10
Razavi, S. H. "Data transmission over TACS cellular radio". Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329178.
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11
Gray, Ashley. "Nonlinearly regenerated long haul data transmission". Thesis, Aston University, 2006. http://publications.aston.ac.uk/8019/.
Testo completoAbstract (sommario):
This thesis experimentally examines the use of different techniques for optical fibre transmission over ultra long haul distances. Its format firstly examines the use of dispersion management as a means of achieving long haul communications. Secondly, examining the use concatenated NOLMs for DM autosoliton ultra long haul propagation, by comparing their performance with a generic system without NOLMs. Thirdly, timing jitter in concatenated NOLM system is examined and compared to the generic system and lastly issues of OTDM amplitude non-uniformity from channel to channel in a saturable absorber, specifically a NOLM, are raised. Transmission at a rate of 40Gbit/s is studied in an all-Raman amplified standard fibre link with amplifier spacing of the order of 80km. We demonstrate in this thesis that the detrimental effects associated with high power Raman amplification can be minimized by dispersion map optimization. As a result, a transmission distance of 1600 km (2000km including dispersion compensating fibre) has been achieved in standard single mode fibre. The use of concatenated NOLMs to provide a stable propagation regime has been proposed theoretically. In this thesis, the observation experimentally of autosoliton propagation is shown for the first time in a dispersion managed optical transmission system. The system is based on a strong dispersion map with large amplifier spacing. Operation at transmission rates of 10, 40 and 80Gbit/s is demonstrated. With an insertion of a stabilizing element to the NOLM, the transmission of a 10 and 20Gbit/s data stream was extended and demonstrated experimentally. Error-free propagation over 100 and 20 thousand kilometres has been achieved at 10 and 20Gbit/s respectively, with terrestrial amplifier spacing. The monitor of timing jitter is of importance to all optical systems. Evolution of timing jitter in a DM autosoliton system has been studied in this thesis and analyzed at bit ranges from 10Gbit/s to 80Gbit/s. Non-linear guiding by in-line regenerators considerably changes the dynamics of jitter accumulation.
12
Butler, Brandon. "Reliable data transfer via frequency transmission". Thesis, Butler, Brandon (2017) Reliable data transfer via frequency transmission. Honours thesis, Murdoch University, 2017. https://researchrepository.murdoch.edu.au/id/eprint/40398/.
Testo completoAbstract (sommario):
Reliable single directional frequency data transfer is a method of electronic communication that is a potential alternative to a bi-directional or wired method. It is intended to determine whether or not single directional data transfer can be designed to perform at the same reliability level as other methods of data transmission. The reason for researching this is to see whether, two-way communication is necessary. Upon finding results to this question it will be determined if single directional frequency data transfer can be as power efficient as bi directional data transfer. It will also look into the overall performance of the method and how it can deal with inhibiting factors that will be introduced to simulate real world external variations in the signal.
How reliable single directional frequency transfer is, will be determined through experiments that are tasked at finding the maximum transmission rate of the devices made and the distance that data transmission can be conducted over.
The investigation will require the design of an experimental apparatus that will allow results to be found in the maximum possible transmission rate and distance transmission can cover.
The experimental apparatus will consist of two possessors, one for encoding a message, the other for decoding a message. The apparatus will also require an integrated radio frequency transmitter circuit as well as a receiver radio frequency integrated circuit. The processors will need to be coded with a new protocol that will allow the incorporation of three forward error correction techniques. This is so that a basic, intermediate and advanced method of forward error correction can be compared when gathering results.
Throughout this research consideration into all aspects that can possibly improve the energy efficiency of the electrical apparatus will be addressed an implemented. By creating an experimental apparatus that is competitive against other data transmission methods in terms of energy efficiency. With an energy efficient experimental apparatus, then results found could be a close representation of the likely outcomes if single directional data transmission was to be implemented on a larger scale.
13
Fu, Haohuan. "Efficient multimedia data transmission over heterogeneous networks /". access full-text access abstract and table of contents, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?mphil-cs-b19887218a.pdf.
Testo completoAbstract (sommario):
Thesis (M. Phil.)--City University of Hong Kong, 2005."Submitted to Department of Computer Science in partial fulfillment of the requirements for the degree of Master of Philosophy." Includes bibliographical references (leaves 105-108).
14
Wu, Min. "Multimedia data transmission for mobile wireless applications". Diss., Columbia, Mo. : University of Missouri-Columbia, 2005. http://hdl.handle.net/10355/4132.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Missouri-Columbia, 2005.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (November 14, 2006) Vita. Includes bibliographical references.
15
Tyrberg, Andreas. "Data Transmission over Speech Coded Voice Channels". Thesis, Linköping University, Department of Electrical Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-6755.
Testo completoAbstract (sommario):
The voice channel in mobile communication systems have high priority and are almost always available. By using the voice channel also for data transmissions it is possible to get the same availability as for voice calls. But due to speech codecs in the voice channel, regular modems can not be used and special techniques are needed to transmit data.
This thesis presents methods to transmit data over the voice channel in a GSM, UMTS or TETRA network. The focus has been on robust data transmission rather than high data bit rates. Approaches are introduced which improve the reliability for transmissions even for systems with low rate speech codecs and channels with some distortion.
The results of the thesis are suggestions of symbol patterns and ways to create and adapt symbols for specific application and channel conditions to achieve the desired goal for the application.
16
Ragonnet-Cronin, Manon Lily. "Transmission networks inferred from HIV sequence data". Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/16151.
Testo completoAbstract (sommario):
HIV in the UK in the 1980s was concentrated within men who have sex with men (MSM) and people who inject drugs (PWID) but heterosexual sex is now the most frequently reported risk behaviour. As these risk groups are associated with different virus populations, this is reflected in the subtype diversification of the UK epidemic, which was historically dominated by subtype B. I have made use of a national database of HIV sequences collected during routine clinical care, which also contains data on age, sex, route of exposure & ethnicity. The 2014 release of the UK HIV Drug Resistance Database contained data from over 60,000 patients. In this thesis, I first describe the development of novel tools that rapidly and automatically identify HIV clusters within phylogenetic trees containing tens of thousands of sequences because they represent transmission chains within the larger infected population. I use these tools to compare the HIV subtype B epidemics in the UK and Switzerland, which had both been described separately but using different approaches. Working with Swiss colleagues, I was able to analyse the epidemics in exactly the same way without having to share sensitive data. I found clustering in the UK to be much higher at relaxed thresholds than in Switzerland (34% vs 16%) indicating that the UK database is more likely to capture transmission chains. Down sampling revealed that this pattern is driven by the larger size of the UK epidemic. At tighter cluster thresholds, the epidemics were very similar. I next use these tools to analyse the spread of emerging subtypes A1, C, D and G in the UK. I found both risk group and cluster size to be predictive of cluster growth, which I tested using simulations and a GLM. Growth of MSM and crossover clusters was significantly higher than expected for subtypes A1 and C, indicating that crossover from heterosexuals to MSM has contributed to their expansion within the UK. Numbers were small for subtypes D and G but the proportion of new diagnoses linking to MSM and crossover clusters was similar to A1 and C, suggesting that the same pattern may be emerging for D and G. I conclude by evaluating the accuracy of a method previously described by our group to generate transmission networks from HIV sequences. The interpretation of clustering patterns from phylogenetic trees is difficult because of the absence of a standardised statistical framework. In contrast, a body of work exists that relates disease transmission to networks. Using large simulated datasets, I developed algorithms which eliminate improbable links. I then reconstructed improved UK transmission networks for subtypes A1, B and C and compare network metrics (such as the degree distribution) between risk groups. Together with other evidence, this thesis demonstrates that the UK HIV epidemic continues to be driven by transmission among MSM. The UK epidemic is no longer compartmentalised and the crossing over of subtypes across risk groups has been facilitated by MSM also having sex with women.
17
Yow, Thiam Poh. "Tunneled data transmission over wireless sensor networks". Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion-image.exe/07Dec%5FYow.pdf.
Testo completoAbstract (sommario):
Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 2007.Thesis Advisor(s): McEachen, John C. ; Tummala, Murali. "December 2007." Description based on title screen as viewed on January 24, 2008. Includes bibliographical references (p. 73-74). Also available in print.
18
Cotruta, Dragos. "Ultra High Data-Rate Optical Transmission Networks". Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104497.
Testo completoAbstract (sommario):
The thesis consists of two different topics: In part 1, the design of an optical system testbed for long haul transmission using a re-circulating loop, is presented. The testbed operates at 40 Gb/s, it simulates an 1800 km link, with optical amplifiers every 80 km, and 16-32 DWDM channels. The theoretical elements involved in the testbed design are reviewed. The optical components are described and selected. The optical system design parameters are presented as well as design targets and optimization parameters. The final implementation is presented and propagation simulations are performed with RZ/NRZ DPSK, QPSK modulation formats to demonstrate the testbed functionality. In part 2 of the thesis, The BER penalty due to PDf in a DPSK demodulator is analyzed and its effect mitigated. A readily available technique is developed that allows measuring the individual contributions of PDf and PDL on BER and calibrate the demodulator in order to reduce the effective PDf by a factor of two which represents an almost 40% reduction in BER penalty due to PDf. The BER penalty due to PDf is measured for 10- vs. 40-GHz, RZ vs. NRZ DPSK demodulators. Finally, PDf mitigation is demonstrated using a PDL emulator, allowing a 75% reduction in polarization sensitivity.La thèse se compose de deux sujets différents: Dans la partie 1, la conception d'un banc d'essai pour simuler un système optique pour la transmission longue distance à l'aide d'une boucle de recirculation, est présentée. Le banc d'essai fonctionne à 40 Gb/s, il simule un lien de 1800 km, avec des amplificateurs optiques à tous les 80km, et 16-32 canaux DWDM. Les éléments théoriques impliqués dans la conception du banc d'essai sont passés en revue. Les composantes optiques sont décrites et sélectionnées. Les paramètres de conception de systèmes optiques sont présentés ainsi que des objectifs de conception et d'optimisation. La mise en œuvre finale est présentée et des simulations de propagation sont réalisées avec les formats de modulation OOK, DPSK, QPSK RZ / NRZ pour démontrer la fonctionnalité du banc d'essai. Dans la partie 2 de la thèse, la pénalité due au PDf dans un démodulateur DPSK est analysée et ses effets réduits. Une technique facilement disponible est développée qui permet de mesurer les contributions individuelles du PDf et PDL sur le BER et de calibrer le démodulateur afin de réduire par un facteur de deux le PDf effectif, ce qui représente une réduction de près de 40% de la pénalité due au PDf sur le BER. La pénalité due au PDf sur le BER est mesurée pour les 10 - 40-GHz vs RZ NRZ dans les démodulateurs DPSK. Enfin, la réduction de la pénalité due au PDF est démontrée en utilisant un émulateur de PDL, ce qui permet une réduction de 75% de la sensibilité à la polarisation.
19
Ammar, Bassem AbuBakr. "Error protection and security for data transmission". Thesis, Lancaster University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421640.
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20
Muhson, Said A. "Digital data transmission over mobile radio channels". Thesis, Loughborough University, 1987. https://dspace.lboro.ac.uk/2134/10838.
Testo completoAbstract (sommario):
The aim of this work is to study data transmission over a microwave digital mobile radio channel at 900 MHz, where the channel is subjected to multipath fading. Besides the fading, the other impairments assumed here are additive noise, co-channel interference and adjacent channel interference. Two modulation techniques are investigated in this work, namely Quadrature-Amplitude-Modulation (QAM) and Quadrature-Phase-Shift- Keying (QPSK). The channel is characterised digitally, assuming multipath Rayleigh fading in the presence of noise. The detection process studied here are near-maximum likelihood schemes: non-linear equalisation methods are also considered in detail. The thesis is also concerned with carrier synchronisation and channel estimation under conditions of Rayleigh fading. Since the carrier syncn,honisation is a most important requirement in mobile radio, a Digital Phase Locked Loop (DPLL) technique has been designed and investigated in the form of a feedback digital synchronisation system. Two types of channel estimation technique, namely feedforward and feedback estimators, are also investigated in this work. The feedback estimator is modified by the addition of a digital control system, in order to reduce its delay, and to cope with rapidly fading signals. Successful carrier synchronisation is demonstrated by the use of space diversity. The study was completed using models of the component parts of the system, and by the use of extensive computer simulations to analyse the system under various operating conditions.
21
Dissanayake, Maheshi Buddhinee. "Error robust video transmission using redundant data". Thesis, University of Surrey, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.521720.
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22
SimoÌ, es LuiÌ s. Miguel Mendes. "Optimal data transmission on MIMO OFDM channels". Thesis, Monterey California. Naval Postgraduate School, 2008. http://hdl.handle.net/10945/3717.
Testo completoAbstract (sommario):
This thesis investigates the Physical Layer performance of single-input single-output (SISO) wireless communications systems, as well as multi antenna techniques such as multiple-input single-output (MISO) and multiple-input multiple-output (MIMO) systems, the last two utilizing the Alamouti-based space-time block coding (STBC) technique. All cases are based on the IEEE 802.16-2004 standard with OFDM using different values of coding rates. International Telecommunications Union (ITU) channel models are selected for the wireless channel in the simulation process. The particular setting we are interested in is the case where partial Channel State Information (CSI) is fed back to the transmitter for optimal control on the transmission rate. The performance results of the simulated SISO, MISO and MIMO systems are compared among themselves.
23
Wong, S. W. "Frequency hopping data transmission at high frequency". Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317262.
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24
ARELLANO, ANDY ALVAREZ. "TRANSMISSION AND RECEPTION OF DATA IN EHF". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=32212@1.
Testo completoAbstract (sommario):
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Nos últimos anos, as bandas de frequências nas comunicações sem fio estão começando a saturar devido ao incremento do tráfego e o aumento dos usuários, é devido a isso que, é necessário estudar as bandas de frequências que não estão sendo utilizadas nas áreas das comunicações como a banda milimétrica e sub-milimétrica. A transmissão de dados na banda EHF o banda milimétrica constitui uma possível solução para conseguir transmitir maiores quantidades de informação a altas velocidades de transmissão aliviando as bandas de frequências atuais. Neste trabalho se estuda a transmissão de dados em frequências de 100, 200, 300 e 400 GHz, empregando a modulação Quadrature Phase-Shift Keying (QPSK) mediante uma arquitetura baseada no batimento de dois lasers, cujas frequências são combinadas em um Beam Splitter, para que a corrente resultante da soma dos campos elétricos dos dois lasers seja convertida em um sinal de alta frequência por meio de uma antena fotocondutora. O batimento dos dois lasers, com diferentes comprimentos de onda e com a mesma potência, ao interagir com uma antena fotocondutora dá como resultado uma frequência na ordem de Gigahertz. No experimento utilizaram-se dois tipos de diodos receptores, um de banda larga (menor que 4 GHz) e outro de banda estreita (menor que 1 MHz). As duas antenas foram testadas em diferentes distâncias e com diferentes frequências de portadora para verificar qual delas tinha o melhor desempenho na banda EHF para poder realizar a transmissão de dados.
In recent years, the frequency bands in wireless communications are beginning to saturate due to the increase of traffic and the increase of users, and it for that reason that is necessary to study the frequency bands that are not begin used in the communication areas like millimeter and sub-millimeters bands. Data transmission in the EHF band is a possible solution to be able to transmit large amounts of information at high transmission speeds, alleviating current frequency bands. In this work, the transmission of data in frequencies of 100, 200, 300 and 400 Gigahertz is studied, using Quadrature phase-shift keying (QPSK) modulation with an architecture based on the beat of two lasers, whos frequencies are combined by means of Beam Splitter, so that result of the electric fields of two lasers is converted into a high frequency signal with the aid of a photoconductor antenna. The.beating of the two lasers, with different wavelengths and with the same power, when interacting with a photoconductor antenna results in a frequency in the order of Gigahertz. In the experiment, two types of receiver diodes were used, one Broadband (less than 4 GHz) and the other of narrowband (less than 1 MHz). The two antennas were tested at different distances and with different carrier frequencies to verify which one had the best performance in the EHF band in order to perform the data transmission.
25
Marple, Steven Robert. "Improved error control techniques for data transmission". Thesis, Lancaster University, 2000. http://eprints.lancs.ac.uk/8074/.
Testo completoAbstract (sommario):
Error control coding is frequently used to minimise the errors which occur naturally in the transmission and storage of digital data. Many methods for decoding such codes already exist. The choice falls mainly into two areas: hard-decision algebraic decoding, a computationally-efficient method, and soft-decision combinatorial decoding, which although more complex offers better error-correction. The work presented in this Thesis is intended to provide practical decoding algorithms which can be implemented in real systems. Soft-decision maximum-likelihood decoding of Reed-Solomon codes can be obtained by using the Viterbi algorithm over a suitable trellis. Two-stage decoding of Reed-Solomon codes is presented. It is an algorithm by which near-optimum performance may be achieved with a complexity lower than the Viterbi algorithm. The soft-output Viterbi algorithm (SOVA) has been investigated as a means of providing soft-decision information for subsequent decoders. Considerations of how to apply SOVA to multi-level codes are given. The use of SOVA in a satellite downlink channel is discussed. The results of a computer simulation, which showed a 1.8dB improvement in coding gain for only a 20% increase in decoding complexity, are presented. SOVA was also used to improve the decoding performance when applied to an RS product code. Several different decoding methods were evaluated, including cascade decoding, and a method where the row and columns were decoded alternately. A complexity measurement was developed which allows accurate comparisons of decoding complexity for trellis-based and algebraic decoders. With this technique the decoding complexity of all the algorithms implemented are compared. Also included in the comparison are the Euclidean and Berlekamp-Massey algorithms.
26
Gouveia, Francisco de. "Transmission and presentation of medical sensor-data". Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/11767.
Testo completoAbstract (sommario):
Mestrado em Sistemas de InformaçãoThis document covers the design, implementation and evaluation of a system that receives, processes and presents live streams of vital signs from sensors attached to a person’s body or in his surrounding environment. This is used either to prevent, analyse and/or act upon a critical scenario of emergency. Due to this critical scenarios where the system can be used, a distributed approach is implemented. Its aim is to reduce the risk of failure and give the possibility of transparent resource scaling according to the needs. Moreover, it is fully modularized for feature extensability and multiple sensor type support. Its Web interface is meant to provide a multi-platform access to the system, as long as the platform has a browser installed. It has a responsive design, according to the screen size of the client device, be it a smartphone, a tablet or a desktop computer. Given the maturity of Web applications and services available, it is easy to add the support for different visualization frameworks or services.
Este documento apresenta o design, implementação e avaliação de um sistema que recebe, processa e apresenta emissões instantâneas de dados vitais de sensores ligados a uma pessoa ou ao meio em que esta se insere. Este é usado para prevenção, análise e/ou acção perante uma situação de emergência. Dados os cenários críticos one o sistema pode ser usado, este é composto por uma arquitectura distribuída, com o intuito de reduzir o risco de o sistema parar por alguma falha, e dar a possibilidade de expandir ou reduzir a capacidade de processamento de acordo com a necessidade de utilização. Além disso, é também um sistema completamante modular e suporta o desevolvimento de módulos com novas funcionalidades ou suporte para diferentes tipos de sensores. A sua interface Web permite o acesso ao sistema, independentemente da plataforma utilizada, desde que esta tenha um browser. Está preparada para ter um design responsivo, de acordo com o tamanho do ecrã do dispositivo, seja um telemóvel, um tablet ou um computador de mesa. Dada a maturidade das aplicações e serviços Web disponíveis, é fácil extender também a interface para suportar novoso tipos de visualizações de informação.
Diese Arbeit behandelt Design, Implementierung und Evaluation eines Systems, das live übertragene Vitalparameter von Sensoren empfängt, verarbeitet und darstellt, die an einem menschlichen Körper angebracht sind oder in seiner Umgebung. Es wird genutzt um kritischen Unfallszenarien vorzubeugen, sie zu analysieren und/oder auf sie zu reagieren. Aufgrund dieser kritischen Szenarien, in denen das System genutzt werden kann, wird ein verteilter Ansatz implementiert. Das Ziel ist es die Fehlerrate zu reduzieren und, bedarfsabhängig, die Möglichkeit zur tranparenten Skalierung der Ressourcen zu geben. Desweiteren ist das System voll modularisiert, um Erweiterbarkeit und die Unterstützung vieler Sensortypen zu gewährleisten. Das Webinterface bietet Zugang von verschiedensten Plattformen, solange ein Browser installiert ist. Es hat ein responsives Webdesign, dass sich and die Bildschirmgröße jedes Nutzergerätes anpasst, sei es ein Smartphone, Tablet oder Desktop Computer. Der gegebene Reifegrad von Webapplikationen und -diensten ermöglicht die Unterstützung verschiedener Visualisierungsframeworks oder -dienste.
27
Simões, Luís Miguel Mendes. "Optimal data transmission on MIMO OFDM channels". Monterey, Calif. : Naval Postgraduate School, 2008. http://edocs.nps.edu/npspubs/scholarly/theses/2008/Dec/08Dec%5FSimoes.pdf.
Testo completoAbstract (sommario):
Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 2008.Thesis Advisor(s): Cristi, Roberto. "December 2008." Description based on title screen as viewed on January 30, 2009. Includes bibliographical references (p. 81-82). Also available in print.
28
Rizk, Ziad. "Digital data transmission over an HF channel". Thesis, Loughborough University, 1996. https://dspace.lboro.ac.uk/2134/7232.
Testo completoAbstract (sommario):
The thesis is concerned with detection, estimation techniques and a method of the adaptive adjustment of the equaliser, for use in a 4800bit/sec synchronous digital transmission system operating over a voice-band time-varying HF channel. Two main impairments are additive Gaussian noise and inter-symbol interference (ISI), which can be very severe at times. All techniques considered here are algorithms or processes that operate on sequences of sample values. Modern digital modems normally operate in this way, and the techniques described are of direct application to practical systems, and could be implemented using the new technology of high speed real-time digital signal processing (DSP). The performance of the various systems that employ the above techniques are obtained using the computer simulated model of three types of HF channels. The ionospheric propagation medium, the characteristics of HF channel and the signal distortion introduced by the channel are first described. The thesis then presents a suitable base-band model of the HF channel for computer simulation of quadrature amplitude modulation systems. A suitable method for the adjustment of the receiver is described next. This method is suitable both for the adjustment of a conventional decision feedback equaliser (DFE), and also for the adjustment of a linear feedforward filter that is employed ahead of a near-maximum likelihood (NML) detector. This method uses a minimum phase (root-finding) algorithm (MPA) to convert the channel response from being non-minimum phase to at least approximately minimum phase. The results of computer simulation tests of this algorithm are then presented over different types of HF channel models. The results demonstrate the algorithm's capability to make the channel response minimum (or near-minimum) phase. Various NML detectors, derived from the Viterbi detector, are discussed. Each detector is here preceded by an adaptive linear filter that is adjusted adaptively using an MPA. The performance of these detectors is compared with the conventional DFE, whose tap-gains are adjusted adaptively using an MPA, and the detector which gives the best compromise between performance and complexity is selected for combined receivers. These results are obtained using perfect estimation of the channel response. The estimation techniques studied in this thesis include both new and conventional estiniators, which are based on the least- mean-square (LMS) algorithm or recursive least-square(RLS) algorithm. The estimator provides an estimate of the sampled impulse response (SIR) of the channel, necessary for the NML detector or MPA. The performances of these estimators are compared using computer simulation tests. The results also demonstrate that the simpler LMS algorithm with adaptive step size gives a comparable level of accuracy with the more complex RLS algorithm. Finally the most promising of the detectors and estimators are connected with an adaptive equaliser, using an MPA, to form a new combined receiver. The details of the combined system structure with its computational complexity are given. Extensive computer simulation tests have been carried out on the different arrangements of the combined system including DFE, when all the functions of detection, estimation and MPA are present, in order to find the most cost effective system in terms of performance and complexity. A considerable reduction in the equipment complexity can be achieved by allowing a long period between successive adjustment of the adaptive filter and estimator.
29
LOMBARDI, FLAVIO. "Reliable Secure Multicast Data Transmission and Applications". Doctoral thesis, La Sapienza, 2005. http://hdl.handle.net/11573/917049.
Testo completo
30
Siu, Yun-ming. "Design and performance analysis of data broadcasting systems /". Hong Kong : University of Hong kong, 1995. http://sunzi.lib.hku.hk/hkuto/record.jsp?B16027115.
Testo completo
31
Lord, Dale, e Kurt Kosbar. "An Architecture for Sensor Data Fusion to Reduce Data Transmission Bandwidth". International Foundation for Telemetering, 2004. http://hdl.handle.net/10150/605790.
Testo completoAbstract (sommario):
International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, CaliforniaSensor networks can demand large amounts of bandwidth if the raw sensor data is transferred to a central location. Feature recognition and sensor fusion algorithms can reduce this bandwidth. Unfortunately the designers of the system, having not yet seen the data which will be collected, may not know which algorithms should be used at the time the system is first installed. This paper describes a flexible architecture which allows the deployment of data reduction algorithms throughout the network while the system is in service. The network of sensors approach not only allows for signal processing to be pushed closer to the sensor, but helps accommodate extensions to the system in a very efficient and structured manner.
32
Salous, Mounther N. H. "Context-based image transmission". Thesis, University of Birmingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368121.
Testo completo
33
Tay, Yeong Kiang Winston. "A performance analysis of management information due to data traffic provisioning in a SONET/SDH communications network". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Jun%5FTay.pdf.
Testo completo
34
Hicks, William T. "IN FLIGHT DATA REDUCTION FOR REDUCED BANDWIDTH TRANSMISSION". International Foundation for Telemetering, 1995. http://hdl.handle.net/10150/608423.
Testo completoAbstract (sommario):
International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, NevadaThe desire to acquire large quantities of high speed vibration and acoustic data during aircraft testing is usually satisfied through on-board high speed recording methods. However there is often a need to have some of this data instantly available at the ground station for flight safety and other purposes. A Data Processor (DP) has been developed allowing an airborne data acquisition system to acquire large amounts of wideband analog data, process the data in real-time, and develop reduced bandwidth information from high bandwidth channels. The reduced data can be inserted into a Pulse Code Modulation (PCM) stream and telemetered via a Radio Frequency (RF) link with a potential for a 2000:1 reduction in bandwidth. This on-board processing capability also lends itself to additional tasks such as the generation of a reduced bandwidth marker channel which can flag critical time periods of data activity. This flagging technique can be used to facilitate ground station analysis of specific segments of data, resulting in significant cost and time savings.
35
Tan, B. T. "Digital transmission using transform techniques". Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384556.
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36
蕭潤明 e Yun-ming Siu. "Design and performance analysis of data broadcasting systems". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1995. http://hub.hku.hk/bib/B3123530X.
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Hinterseer, Martin, e Christoph Wegscheider. "ACQUISITION AND TRANSMISSION OF SEISMIC DATA OVER PACKET RADIO". International Foundation for Telemetering, 2005. http://hdl.handle.net/10150/605056.
Testo completoAbstract (sommario):
ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, NevadaResearch on earthquakes and volcanos is of particular importance in seismic instable regions. To improve opportunities of research and civil defence, continuous coverage of seismic activities of a large area at a certain time is necessary. This paper deals with the issues concerning the collecting of environmental data by a number of autonomous field stations and their transmission to central station through a cost effective low bandwidth packer radio data network. This paper deals with the acquisition, preprocessing and transmission of seismic data. Therefore, a prototype system is discussed, which will be developed at the University of Salzburg, Austria.
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Yamout, Salam 1963. "A NEW COMBINED ROUTING AND FLOW CONTROL ALGORITHM FOR DATA COMMUNICATION NETWORKS". Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276558.
Testo completoAbstract (sommario):
The object of interest in this research is the evaluation of the combined routing and flow control scheme proposed by Muralidhar and Sundareshan. A slightly modified design using results from positive system theory is proposed as an attempt to improve the performance. Then a detailed performance evaluation of Muralidhar and Sundareshan's scheme and its modified version proposed here is conducted using discrete-event simulation. The application of positive system theory to the combined routing and flow control algorithm proposed by Muralidhar and Sundareshan proved to be quite effective in improving the overall performance only in the initial transient period. The fact that the improvement is restricted to a particular time period appears to be attributable to poor buffer management and certain other fundamental problems with Muralidhar and Sundareshan's scheme. These problems are identified and are described in detail.
39
Lee, Man-yiu. "Implementation of government related electronic trade document services in Hong Kong /". Hong Kong : University of Hong Kong, 1997. http://sunzi.lib.hku.hk/hkuto/record.jsp?B18831242.
Testo completo
40
Motahari, Bidgoli Seyed Mohammad Amin. "An Optical Design Configuration for Wireless Data Transmission". FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2439.
Testo completoAbstract (sommario):
The concept of 2D barcodes is of great relevance for use in wireless data transmission between handheld electronic devices. In a typical setup, any file on a cell phone for example can be transferred to a second cell phone through a series of images on the LCD which are then captured and decoded through the camera of the second cell phone. In this research, a new approach for data modulation in 2D barcodes is introduced, and its performance is evaluated in comparison to other standard methods of barcode modulation. In the proposed method, Orthogonal Frequency Division Multiplexing (OFDM) modulation is used together with Differential Phase Shift Keying (DPSK) over adjacent frequency domain elements to modulate intensity of individual pixels. It is shown that the bit error rate performance of the proposed system is superior to the current state of the art in various scenarios. A specific aim of this study is to establish a system that is proven tolerant to camera motion, picture blur and light leakage within neighboring pixels of an LCD. Furthermore, intensity modulation requires the input signal used to modulate a light source to be positive, which requires the addition of a dc bias. In the meantime, the high crest factor of OFDM requires a lower modulation index to limit clipping distortion. These two factors result in poor power efficiency in radio over fiber applications in which signal bandwidth is generally much less than the carrier frequency. In this study, it is shown that clipping a bipolar radio frequency signal at zero level, when it has a carrier frequency sufficiently higher than its bandwidth, results in negligible distortion in the pass band and most of the distortion power is concentrated in the baseband. Consequently, with less power provided to the optical carrier, higher power efficiencies and better receiver sensitivity will result. Finally, a more efficient optical integrated system is introduced to implement the proposed intensity modulation method which is optimized for radio over fiber applications.
41
Haddad, Nicholas. "Transmission of digital images using data-flow architecture". Ohio : Ohio University, 1985. http://www.ohiolink.edu/etd/view.cgi?ohiou1184007755.
Testo completo
42
Zarimpas, Vasileios. "Multimedia data transmission over multiple wireless communication channels". Thesis, Lancaster University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.497216.
Testo completoAbstract (sommario):
Modern mobile applications demand a communications network that is universally accessible at any time and able to adapt to the application needs. Meeting these requirements can present a considerable challenge. In order to access information ubiquitously, hardware manufacturers started to integrate many network access technologies in single small, light and low-power portable device. The main objective of this thesis is to exploit the availability of multiple wired and wireless communication channels for multimedia data transmission and location based services.
43
Nelson, Christopher J. "Low complexity capacity-approaching codes for data transmission". Thesis, Lancaster University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.556663.
Testo completoAbstract (sommario):
This thesis analyzes the design of low complexity capacity approaching codes suitable for data transmission. The research documented in this thesis describes new and novel design methods for three well-known error control coding techniques, Turbo codes, LDPC block codes and LDPC convolutional codes, which are suitable for implementation in a number of modem digital communication systems. Firstly, we present Partial Unit Memory (PUM) based Turbo codes. A variant of Turbo codes which encompasses the advantages of both block and convolutional codes. The design methods of PUM Turbo codes are presented and Bit Error Rate (BER) simulations and Extrinsic Information Transfer (EXIT) chart analysis illustrates their performance. Partial Unit Memory codes are a class of low complexity, non-binary convolutional codes and have been shown to outperform equivalent convolutional codes. We present the EXIT charts of parallel concatenated PUM codes and PUM Woven Turbo Codes and analyse them to assess their performance compared with standard Turbo code designs. Resulting Extrinsic Information Transfer charts indicate that the proposed PUM-based codes have higher mutual information during iterative decoding than the equivalent Recursive, Systematic, Convolutional Turbo codes (RSC- TC) for the same Eb/No, i.e. the output of the decoders provides a better approximation of the decoded bits. The EXIT chart analysis is supported by BER plots, which confirms the behaviour predicted by the EXIT charts. We show that the concatenated PUM codes outperform the well-known turbo codes in the waterfall region, with comparable performance in the error floor region. In the second section we present Low Density Generator Matrix codes; a variant of LDPC codes that have low complexity encoding and decoding techniques. We present results of three construction methods and describe how LDGM codes can be modified to improve the error-floor region. We describe the design of random, structured and semi-random, semi- structured codes and how, by replacing the identity matrix with a staircase matrix, LDGM codes can show significant improvements in the error-floor region. Furthermore, we analyse the performance of serially concatenated LDGM codes and how they can benefit when we use the modified LDGM codes in either the outer code or the inner code. The results indicate that concatenated LDGM codes that incorporate LDGM staircase codes in the inner code will show improvements in error-floor performance while maintaining near capacity limit performances. While in the case of LDGM staircase codes being used as the outer codes no significant improvements in waterfall or error-floor regions are observed compared to a concatenated scheme that employs an LDGM identity outer code. Finally, we propose a new design of LDPC convolutional code, which we term as time invariant Low Density Parity Check Unit Memory (LDPC-UM) codes. The performance of LDPC block and Low Density Parity Check Unit Memory codes are compared, in each case, the Low Density Parity Check Unit Memory codes performance is at least as good as that of the LDPC block codes from which they are derived. LDPC-UM codes are the convolutional counterparts of LDPC block codes. Here, we describe techniques for the design of low complexity time invariant LDPC-UM codes by unwrapping the Tanner graph of algebraically constructed quasi-cyclic LDPC codes. The Tanner graph is then used to describe a pipelined message passing based iterative decoder for LDPC-UM codes and standard LDPC convolutional codes that outputs decoding results continuously.
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尹翰卿 e Hon-hing Wan. "Efficient real-time scheduling for multimedia data transmission". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B31227910.
Testo completo
45
Beckmann, Paul Eric. "Difficulties with NTSC compatible quadrature digital data transmission". Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14490.
Testo completoAbstract (sommario):
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1989.Includes bibliographical references (leaves 74-76).
by Paul Eric Beckmann.
M.S.
46
Mubinya, Antone Betrano Omondi. "Techniques to optimise data transmission in optical fibre". Thesis, Cape Peninsula University of Technology, 2011. http://hdl.handle.net/20.500.11838/2203.
Testo completoAbstract (sommario):
Thesis (MTech(Electrical Engineering))--Cape Peninsula University of Technology, 2011.Due to the tremendous growth in data traffic and development in optical fiber transmission technologies, the limits of the transmission capacity available with the conventional and modulation techniques have been surpassed. The present work aims at pointing out in-terms of data transmission that Solitons can effectively be a waveguide of choice in transoceanic optical fiber communication systems. In this thesis Soliton has been identified as the ideal technique for data transmission in long transmission distance. Techniques which have been used in long haul single mode optical fibers to transmit data are discussed and their characteristics mentioned. Solitons which constitutes a balance between chromatic dispersion and SPM is a transmission technique that adapts to instantaneous channel characteristics and significantly improves optical fiber transmission performance. Optical fiber transmission is a technology that has been driven by the demands for streaming data and is increasingly used worldwide in the modern days.ln the standard single mode fiber, Chromatic dispersion is the linear phenomenon whose effect limits maximum transmissions distance. Chromatic dispersion and SPM act simultaneously in optical fiber to generate a solitary pulse wave used in lightwave.
47
Jiang, Jing. "Capacity-approaching data transmission in MIMO broadcast channels". Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/11208.
Testo completoAbstract (sommario):
This dissertation focuses on downlink multi-antenna transmission with packet scheduling in a wireless packet data network. The topic is viewed as a critical system design problem for future high-speed packet networks requiring extremely high spectral efficiency. Our aim is to illustrate the interaction between transmission schemes at the physical layer and scheduling algorithms at the medium access control (MAC) layer from a sum-capacity perspective. Various roles of multiple antennas are studied under channel-aware scheduling, including diversity, beamforming and spatial multiplexing. At a system performance level, our work shows that downlink throughput can be optimized by joint precoding across multiple transmit antennas and exploiting small-scale fading of distributed multiple input and multiple output (MIMO) channels.
There are three major results in this dissertation. First, it is shown that over a MIMO Gaussian broadcast channel, and under channel-aware scheduling, open-loop transmit antenna diversity actually reduces the achievable sum rate. This reveals a negative interaction between open-loop antenna diversity and the closed-loop multiuser diversity through scheduling. Second, a suboptimal dirty paper coding (DPC) approach benefits greatly from multiuser diversity by an efficient packet scheduling algorithm. Performance analysis of a suboptimal greedy scheduling algorithm indicates that, compared with the receiver-centric V-BLAST method, it can achieve a much larger scheduling gain over a distributed MIMO channel. Further, pre-interference cancellation allows for transmissions free of error propagation. A practical solution, termed Tomlinson-Harashima precoding (THP), is studied under this suboptimal scheduling algorithm. Similar to V-BLAST, a reordering is applied to minimize the average error rate, which introduces only a negligible sum-rate loss in the scenarios investigated. Third, for an orthogonal frequency division multiplexing (OFDM) system using MIMO precoding, it is shown that a DPC-based approach is readily applicable and can be easily generalized to reduce the peak-to-average power ratio (PAR) up to 5 dB without affecting the receiver design. Simulations show that in an interference-limited multi-cell scenario, greater performance improvement can be achieved by interference avoidance through adaptive packet scheduling, rather than by interference diversity or averaging alone. These findings suggest that, coordinated with channel-aware scheduling, adaptive multiplexing in both spatial and frequency domains provides an attractive downlink solution from a total capacity point of view.Ph. D.
48
Béraud, Guillaume. "Modelling infectious agent transmission using social mixing data". Thesis, Lille 2, 2015. http://www.theses.fr/2015LIL2S040/document.
Testo completoAbstract (sommario):
L'évaluation économique de nouveaux vaccins exige de modéliser la transmission infectieuse au sein de la population, et donc des hypothèses sur la structure et la répartition des contacts. Les matrices de contact obtenues à partir d’enquête de population ont été déterminées pour 8 pays européens. Mais aucune donnée de ce type n'existe à ce jour pour la France. L’étude ComesF (Contact Matrix Estimation – France) vise à combler cette lacune.MéthodologieL'enquête s’est effectuée sur 3 périodes (Février-Mars, Avril, Mai-Avril) avec 278 participants communs à la première et dernière période. Les participants devaient rapporter tous leurs contacts au cours de 2 jours consécutifs dans un journal, avec l'âge, le sexe, l'endroit, la fréquence, le type et la durée du contact.En combinant des enquêtes sérologiques de 2009 et 2013 et les données de couverture vaccinales, nous avons modélisé la séroprévalence de la rougeole, des oreillons et de la rubéole; puis extrapolé la susceptibilité selon l’âge par département à l'année d'intérêt (2016) ; enfin le potentiel épidémique et l'incidence relative selon l’âge d'une future épidémie ont été estimés.Nous avons analysé l'influence de conditions météorologiques sur les variations temporelles des matrices de contact. La population de l'étude a été analysée selon le jour et la météorologie pour estimer le nombre moyen de contacts et le potentiel de transmission estimée avec le R0. Nous avons effectué une revue systématique de la littérature sur les différences selon le genre pour la grippe, la rougeole, les oreillons et la rubéole, puis exploré l'impact du genre sur les matrices de contact et la modélisation des maladies infectieuses.Résultats2033 participants ont rapporté 38881 contacts (médiane pondérée [premier quartile-troisième quartile] : 8 [5–14] par jour) et 54378 contacts avec les contacts professionnels supplémentaires (9 [5–17]). Contrairement à l'âge, le genre, la taille du foyer, les vacances scolaires, le week-end et l'activité professionnelle, la période de l'année influait peu le nombre de contacts ou les schémas de contact. Les schémas de contact étaient influencés par l'âge indépendamment du lieu de contact, et par le genre, les femmes ayant 8 % plus de contacts que les hommes. La plupart des contacts avaient lieu à la maison et à l'école, mais l'ajout des contacts professionnels modifiait la structure des schémas de contact. Les vacances scolaires et les week-ends réduisaient le nombre de contacts, et le R0 de 33 % et de 28 %, respectivement. Le risque pour les Oreillons et la Rubéole concerne surtout le Sud Est et le Centre de la France, alors que le risque pour la rougeole est plus dispersé. Le risque varie avec le genre pour la Rougeole et la Rubéole. Outre les bébés < 1 an, l’épidémie toucherait surtout les adolescents et les jeunes adultes.Les conditions météorologiques influençaient les schémas de contact différemment entre les jours de semaine ou les weekends. La correction pour analyse répétée limitait le nombre de résultats significatif, mais la tendance pour un effet de la météorologie variant entre les jours de semaine et le week-end restait.Les différences de genre dans le schéma de contact pourraient expliquer en partie les différences de genre dans l'épidémiologie des maladies infectieuses. L'utilisation de données spécifiques par genre avait un impact significatif sur le résultat de la modélisation du risque d’une épidémie.Les matrices de contact françaises partageaient de nombreux points communs avec les autres matrices européennes, notamment avec un impact substantiel des fermetures d’école en cas d’épidémie sur la progression de l’épidémie. Le risque d'une nouvelle épidémie de rougeole persiste, mais prédomine pour les oreillons. L'effet des conditions climatiques sur les schémas de contact était modeste, voire négligeable. L’utilisation des données spécifiques par genre est à considérer en modélisationThe economic evaluation of new vaccines requires the modeling of infectious disease transmission within a population, which in turn requires some assumption of specific mixing patterns. Matrixes generated from social contact studies were determined for 8 European countries. To date, no such data exist for France. The ComesF study (Contact Matrix Estimation – France) aimed to fill this gap.MethodologyThe survey was carried out over 3 different periods (Feb-Mar, Apr, Apr-May) with 278 participants common to the first and the last periods. Participants had to list all their contacts for 2 consecutive days in a diary, with the age, sex, location, frequency, type and duration of the contact, from which we estimated French contact matrixes.Combining cross-sectional serological surveys from 2009 and 2013 and vaccine coverage information, we have determined an optimal model for the serology of measles, mumps and rubella for the year of the data collection; age-dependent susceptibility by department was then derived to the year of interest (2016), and effective reproduction number and age-dependent relative incidence of a potential outbreak were estimated using the French contact matrixes.We analysed the influence of meteorological conditions on the temporal variations in mixing patterns. The population of the study was split according to the day and the weather at the time when the diary was filled in. The mean number of contacts and the potential for transmission summarized with R0 were calculated for type and location of contact under different weather conditions.We conducted a systematic review on gender differences in infection focusing on influenza, measles, mumps and rubella. Finally, we provided an exploration of the impact of gender on mixing patterns, and eventually the potential implication for modelling.ResultsThe 2033 participants reported 38 881 contacts (weighted median [first quartile-third quartile]: 8[5–14] per day), and 54 378 contacts with supplementary professional contacts (9[5–17]). Contrary to age, gender, household size, holidays, weekend and occupation, the period of the year had little influence on the number of contacts or the mixing patterns. Contact patterns were highly assortative with age, irrespective of the location of the contact, and gender, with women having 8% more contacts than men. Although most contacts occurred at home and school, the inclusion of professional contacts modified the structure of the mixing patterns. Holidays and weekends reduced the number of contacts dramatically, and as proxies for school closure, reduced R0 by 33% and 28%, respectively.The risk for Mumps and Rubella mainly concerned southeastern and south central France, while the risk for measles was more scattered over the country. Risk differed with gender for Measles and Rubella. Besides infants under 1, the highest share of participation would concern teenagers and young adults.The weather had a differential effect on social mixing according to the type of day, notably weekdays and weekend. But correction for repeated analysis made some results no more significant, although the trend for a differential effect between weekdays and weekend remained.Gender differences in social mixing might explain some gender differences in infectious disease epidemiology. Using gender-specific susceptibility and gender-specific contact matrixes had a significant impact on the result of the modeling. Despite the differences, French contact matrixes shared many aspects with those of other European countries. Notably, school closures were likely to have a substantial impact on the spread of close contact infections in France. While the risk of a new Measles outbreak persists, it predominates for Mumps. The effect of weather on social mixing was mild, if not negligible. Gender differences in modelling should be emphasized
49
Ursini, Leonora. "Optical Chaotic Transmission Systems For Secure Data Communication". Doctoral thesis, Università degli studi di Padova, 2009. http://hdl.handle.net/11577/3425929.
Testo completoAbstract (sommario):
The optical chaos dynamics are investigated for obtaining the secure transmission of an information message. A detailed
numerical analysis of an optical chaotic transmission system, based on the synchronization of two chaotic lasers is presented. At the transmitter, the chaotic waveform is superposed on the information message; at the receiver, the message is recovered by subtracting the synchronized chaotic wave from the received signal. The aim is the investigation of the system performance for various configurations. Original
methods are also proposed for improving the performance. Finally, an experimental set-up of the chaotic transmission system has been implemented.L'attività di Ricerca, presentata in questa Tesi, è stata parte del Progetto di Rilevante Interesse Nazionale (PRIN), finanziato dal Ministero dell'Università e della Ricerca, e intitolato ``Trasmissione in fibra ottica su portante ottica caotica'' (PRIN200509125), svolto in collaborazione fra le Università di Padova, Pavia e l'Aquila. La protezione nel trasferimento delle informazioni è, da sempre, una delle caratterisctiche più richieste ai mezzi di comunicazione. I metodi sia crittografici che steganografici, atti a garantire sicurezza agli utenti che scambiano in rete dati sensibili, costituiscono un grosso filone di ricerca. Lo scopo di questa Tesi è dimostrare la comunicazione di un messaggio su un canale in fibra ottica, utilizzando una tecnica che si basa sul principio di sincronizzazione di una coppia di laser, operanti nel regime caotico. Il caos deterministico è un regime di alcuni sistemi dinamici non-lineari, che si caratterizza con evoluzioni irregolari, fortemente dipendenti dalle condizioni iniziali. Il regime caotico, nei laser, si manifesta con rapide ed apparentemente casuali oscillazioni della forma d'onda emessa. Nello schema di trasmissione, il trasmettitore è costituito da un generatore di messaggi e da un laser caotico, detto master, che funge da portante ottica; il messaggio d'informazione da trasmettere è opportunamente sovrapposto all'emissione del master, realizzando uno schema di protezione di tipo steganografico. Al ricevitore, l'estrazione del messaggio si basa sulla disponibilità di un altro laser, detto slave, che generi un'identica forma d'onda caotica (sincronizzazione), da sottrarre al segnale trasmesso. Perchè ciò sia possibile, data la forte dipendenza del caos dalle condizioni iniziali e dai valori dei parametri dei laser, è necessario disporre di una coppia di laser avente parametri molto simili. Questo fatto, aggiunto ad una efficiente mascheratura del messaggio, rende molto difficile la decodifica da parte di un ascoltatore non autorizzato. L'efficacia di tale tecnica si basa sulla qualità della sincronizzazione, che può degradarsi, oltre che per una scelta non corretta dei due laser, anche per gli effetti distorsivi della fibra ottica su cui si trasmette il segnale, come attenuazione, dispersione cromatica, effetti nonlineari e di polarizzazione, e dal rumore. In questa Tesi, si è studiato, da un punto di vista teorico e numerico il sistema caotico su fibra ottica, analizzandone le prestazioni per varie configurazioni. Lo studio ha riguardato: la generazione del caos di un laser a semiconduttore, mediante retroriflessione del segnale con uno specchio esterno; l'analisi della sincronizzazione con un laser gemello; la modellizzazione del canale ottico; l'analisi delle prestazioni del sistema caotico per la steganografia di messaggi digitali. Nella Tesi, sono anche presentati metodi originali per migliorare le prestazioni di sicurezza e recupero del messaggio. Infine, è stato implementato anche un dimostratore del sistema, in collaborazione con l'Università di Pavia.
50
Chung, Koo-Don. "Data transfer over multiplexed logical data links sharing a single physical circuit". Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/9201.
Testo completo