Teses / dissertações sobre o tema "Techniques de transmission"
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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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Qi, Yinan. "Single relay cooperative transmission/reception techniques". Thesis, University of Surrey, 2009. http://epubs.surrey.ac.uk/843759/.
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One of primary objectives of future wireless systems is to provide uniform high rate coverage. Essentially, a wireless system must take multipath fading, path loss and shadowing effect into consideration. In the pursuit of schemes that will provide a solution to these problems, various granular and distributed network architectures based on relaying techniques are emerging. In particular, three basic relaying schemes have been proposed including amplify-and-forward (AF), decode-and-forward (DF) and compress-and-forward (CF). This thesis has investigated the performance of various single-relaying schemes from the theoretical point of view and established a fundamental understanding of relay-assisted communication systems. An improved version of DF - Soft DF - has been evaluated through the derived upper bounds of Bit-Error-Rate (BER) and Block-Error-Rate (BLER). For the most complicated relaying scheme - CF, we proposed some novel techniques to efficiently improve its performance. Moreover, both theoretic and simulation results have shown that one single-relaying scheme cannot always outperform the others over all channel conditions. In this regard, the relaying schemes need to be deployed in a hybrid fashion to adapt to the current channel realization. We have provided two hybrid relaying schemes in this thesis and investigated the integration of the hybrid relaying schemes with hybrid retransmission protocols. The proposed integrated technique is named as H2-ARQ-Relaying schemes. Moreover, we have proposed two H2-ARQ-Relaying strategies that efficiently exploit a hybrid CF/DF forwarding scheme, where the relay, based on its decoding status, could dynamically switch between CF and DF and analyzed the performance analysis has been performed for both strategies mainly in terms of the obtained outage probabilities and throughputs. Considering the availability of Channel State Information (CSI) at the relay in practical implementations, we have proposed modified CF/DF-based H2-ARQ-Relaying strategies with limited CSI feedback accordingly.
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Marple, Steven Robert. "Improved error control techniques for data transmission". Thesis, Lancaster University, 2000. http://eprints.lancs.ac.uk/8074/.
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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.
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Lee, Y. W. A. "Advanced optical techniques for high capacity transmission". Thesis, Aston University, 2003. http://publications.aston.ac.uk/8001/.
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This thesis presents several advanced optical techniques that are crucial for improving high capacity transmission systems. The basic theory of optical fibre communications are introduced before optical solitons and their usage in optically amplified fibre systems are discussed. The design, operation, limitations and importance of the recirculating loop are illustrated. The crucial role of dispersion management in the transmission systems is then considered. Two of the most popular dispersion compensation methods - dispersion compensating fibres and fibre Bragg gratings - are emphasised. A tunable dispersion compensator is fabricated using the linear chirped fibre Bragg gratings and a bending rig. Results show that it is capable of compensating not only the second order dispersion, but also higher order dispersion. Stimulated Raman Scattering (SRS) are studied and discussed. Different dispersion maps are performed for all Raman amplified standard fibre link to obtain maximum transmission distances. Raman amplification is used in most of our loop experiments since it improves the optical signal-to-noise ratio (OSNR) and significantly reduces the nonlinear intrachannel effects of the transmission systems. The main body of the experimental work is concerned with nonlinear optical switching using the nonlinear optical loop mirrors (NOLMs). A number of different types of optical loop mirrors are built, tested and implemented in the transmission systems for noise suppression and 2R regeneration. Their results show that for 2R regeneration, NOLM does improve system performance, while NILM degrades system performance due to its sensitivity to the input pulse width, and the NALM built is unstable and therefore affects system performance.
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Ramirez, Gutierrez Raymundo. "Transmission and detection techniques for MIMO systems". Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/8119/.
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It is well-known that Multiple-Input Multiple-Output (MIMO) wireless systems are disposed by two conclusive goals: high data rate and high performance. This thesis is concerned with transmission and detection techniques of MIMO systems, particularly on Spatial Modulation (SM). SM is a lately developed transmission technique for multiple antenna systems. The idea behind SM is to map a block of information bits into two parts, carried separately by the index of the active transmitter and the symbol chosen from constellation points. All four transmission techniques presented in this thesis are based on the SM principle. The first system, called spatial phase shift keying (SPSK) modulation, follows the idea of SM but uses multiple active transmitters and it shows a gain of 2 dB over a transmission technique based on SM. Antenna beam pattern modulation (ABPM) is the second proposed technique. In this technique, the antenna beam patterns are utilised to transmit information. The contribution of this scheme is to improve the data rate utilizing different beam patterns in order to generate another dimension to the constellation diagram. Optimization of the beam pattern design results in improved system performance. In addition to all the benefits of ABPM at the transmission design, a sub-optimal detection method based on lattice reduction (LR) is used to reduce the computational complexity in comparison to the optimal maximum likelihood (ML) method. The aim of this proposed sub-optimal detection method (LR) is to achieve performance similar to that of the ML scheme at affordable complexity. ABPM shows a gain of more than 2 dB over transmission techniques based on SM. The third scheme is called antenna pattern shift keying (APSK) modulation. This scheme combines the idea of SPSK and ABPM because the antenna beam patterns and the indices of the active transmitters carry the symbol chosen from a constellation diagram. APSK improves the data rate and the overall system performance. APSK has similar performance as a spatial multiplexing scheme but APSK reduces the number of RF chains and it has a gain of 3.5 dB in comparison to that of a technique based on SM. The last scheme included in this thesis, is a precoder technique based on LR. This novel LR pre-coder is applied to the generalised pre-coding aided spatial modulation (GPSM) scheme to improve the system’s performance and it shows a gain of more than 1 dB over the traditional GPSM. Additionally, a suboptimal detector scheme is proposed to achieve performance similar to that of the ML detector but with lower complexity. Using that in combination with the LR pre-coding technique means that the performance of the GPSM scheme is preserved with a much lower detection complexity.
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Taylor, Alistair James Eden. "Techniques for power system simulation using multiple processors". Thesis, Durham University, 1990. http://etheses.dur.ac.uk/5963/.
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The thesis describes development work which was undertaken to improve the speed of a real-time power system simulator used for the development and testing of control schemes. The solution of large, highly sparse matrices was targeted because this is the most time-consuming part of the current simulator. Major improvements in the speed of the matrix ordering phase of the solution were achieved through the development of a new ordering strategy. This was thoroughly investigated, and is shown to provide important additional improvements compared to standard ordering methods, in reducing path length and minimising potential pipeline stalls. Alterations were made to the remainder of the solution process which provided more flexibility in scheduling calculations. This was used to dramatically ease the run-time generation of efficient code, dedicated to the solution of one matrix structure, and also to reduce memory requirements. A survey of the available microprocessors was performed, which concluded that a special-purpose design could best implement the code generated at run-time, and a design was produced using a microprogrammable floating-point processor, which matched the code produced by the earlier work. A method of splitting the matrix solution onto parallel processors was investigated, and two methods of producing network splits were developed and their results compared. The best results from each method were found to agree well, with a predicted three-fold speed-up for the matrix solution of the C.E.G.B. transmission system from the use of six processors. This gain will increase for the whole simulator. A parallel processing topology of the partitioned network and produce the necessary structures for the remainder of the solution process.
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Kempson, C. N. "Statistical techniques for digital modulation recognition". Thesis, Cranfield University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277938.
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Automatic modulation recognition is an important part of communications electronic monitoring and surveillance systems where it is used for signal sorting and receiver switching. ' This thesis introduces a novel application of multivariate statistical techniques to the problem of automatic modulation classification. The classification technique uses modulation features derived from time-domain parameters of instantaneous signal envelope, frequency and phase. Principal component analysis (PCA) is employed for data reduction and multivariate analysis of variance (MANOVA) is used to investigate the data and to construct a discriminant function to enable the classification of modulation type. MANOVA is shown to offer advantages over the techniques already used for modulation recognition, even when simple features are used. The technique is used to construct a universal discriminator which is independent of the unknown signal to noise ratio (SNR) of the received signal. The universal discriminator is shown to extend the range of signal-to-noise ratios (SNRs) over which discrimination is possible, being effective over an SNR range of 0-4OdB. Development of discriminant functions using MANOVA is shown to be an extensible technique, capable of application to more complex problems. i
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Bejile, Brian. "Bi-level lossless compression techniques". Diss., Connect to the thesis, 2004. http://hdl.handle.net/10066/1481.
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Thornton, Louise. "Error robust coding techniques for mobile video transmission". Thesis, University of Strathclyde, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248727.
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VALE, EDUARDO RODRIGUES. "TECHNIQUES FOR VOICE TRANSMISSION IMPROVEMENT IN UMTS SYSTEMS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2006. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=8933@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROA partir da necessidade do transporte de informação multimídia, foram desenvolvidos os Sistemas Celulares de Terceira Geração, ainda em fase de padronização, cujo candidato mais promissor é o UMTS (Universal Mobile Telecommunications System). De forma consonante com a tendência mundial de utilização crescente da tecnologia IP (Internet Protocol) nas redes fixas, o UMTS veio a incorporar este protocolo, que apresenta uma maior flexibilidade para a introdução de novos serviços. Assim, na arquitetura do UMTS existem atualmente dois modos de transmissão, a Comutação de Circuitos e a Comutação de Pacotes. Esta Tese de Doutorado descreve, inicialmente, os processos de estabelecimento de chamadas de voz no UMTS, tanto na modalidade de Comutação de Circuitos como na de Comutação de Pacotes. Em seguida, procura fazer uma avaliação comparativa da eficiência na execução de chamadas de voz nestas duas modalidades, com ênfase de aplicação no sentido uplink de transmissão. Neste processo, são desenvolvidas várias formas de otimização de desempenho da transmissão na interface aérea do UMTS, em particular na Comutação de Pacotes, visando tornar este modo de transmissão competitivo com o modo de Comutação de Circuitos em termos de eficiência na transmissão de voz. Embora o tratamento aqui apresentado se refira ao UMTS-FDD (UMTS Frequency Division Duplex), as técnicas aqui desenvolvidas também encontram aplicação em outros Sistemas Celulares de Terceira Geração congêneres, tal como o CDMA 2000.
With the advent of multimedia traffic, Third Generation mobile systems were introduced, with the UMTS as the most promissor candidate. In consonance with the global trend of utilization of the IP technology in fixed networks, the UMTS developers decided to incorporate this protocol, which presents more facilities for the introduction of new services. Therefore, the UMTS architecture has two transmission modes: Circuit Switching and Packet Switching Modes. This Doctoral Dissertation initially describes the call setup processes (call flows) for those transmission modes. It follows a comparative evaluation of the efficiency aspect related to calls executed in both modes, considering the case of uplink transmission. In this process, several optimization techniques are introduced, aiming at the improvement of energy consumption in the air interface. The final objetive is to turn the Packet Switching Mode competitive with the Circuit Switching Mode, relative to the energy consumed for the transmission of voice calls. Though the treatment here presented refers to the UMTS-FDD technology, all the results are equally applicable to other similar systems, like the CDMA- 2000.
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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.
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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.
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Bejiani, Elie. "Techniques de transmission pour les canaux très dispersifs". Paris, ENST, 1997. http://www.theses.fr/1997ENST0044.
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La transmission efficace des informations sur les canaux fortement dispersifs (canal Hf, canal acoustique sous-marin) reste un problème ouvert. Nous proposons dans cette thèse des idées nouvelles permettant la réalisation de systèmes plus performants en débit ainsi qu'en robustesse. Le degré de dispersive d'un canal de transmission est généralement traduit par le facteur d'étalement (spread factor) l = bd tm, ou bd désigne la bande du spectre doppler, et tm l'étendue temporelle des multi trajets. L'égalisation (sous des formes diverses) est considérée depuis longtemps comme l'unique réponse au problème pose par les transmissions cohérentes sur les canaux a évanouissements sélectifs. Nous montrons quantitativement les limites intrinsèques des systèmes a égaliseurs, interdisant leur fonctionnement au-delà de l = 0. 01. En revanche, les systèmes à porteuses multiples associent à une estimation du canal (rendu non sélectif) par les symboles pilotes, constituent une alternative très intéressante. Forts des résultats précédents, nous proposons un système de transmission complet a porteuses multiples, dans lequel l'estimation du canal est effectuée symbole par symbole. Ceci est possible grâce à l'insertion dans le même intervalle de temps ts, d'un symbole d'information et d'un symbole pilote, à l'aide de deux fonctions orthogonales bien localisées en temps et en fréquence (fonctions protale sphéroïdales). Cette approche a l'avantage d'être à la fois robuste et efficace. Elle permet de transmettre de l'information convenablement sur des canaux dont le facteur d'étalement l atteint 0,2. Lorsque le canal est très étale, ou même sur-étale (l > 1), les modulations non cohérentes s'imposent. Cependant, les transmissions non cohérentes souffrent de leur faible efficacité spectrale. Ainsi nous proposons une technique de transmission par signaux multidimensionnels a composantes corrélées qui permet d'augmenter considérablement cette efficacité spectrale tout en garantissant des performances au moins aussi bonnes que les solutions classiques équivalentes. Par ailleurs, nous nous intéressons au calcul de la capacité du canal de rayleigh en détection non cohérente. Nous montrons que cette capacité est finie même en absence du bruit additif.
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QIN, LING. "Perfectionnement aux techniques de transmission à porteuses multiples". Paris, CNAM, 1998. http://www.theses.fr/1998CNAM0332.
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Les techniques de transmissions multiporteuses, en divisant un canal en un grand nombre de sous-canaux, permettent de s'affranchir des distorsions et d'ajuster le debit binaire transmis a la densite spectrale du bruit, et d'atteindre ainsi des debits eleves sur des canaux tres perturbes. Dans le present memoire des perfectionnements sont proposes et etudies, dans le cadre d'une evolution vers les bancs de filtres, qui permettent de supprimer les temps de garde et d'effectuer une egalisation des sous-canaux. L'apport principal du travail decrit est l'introduction et l'etude de l'egaliseur de sous-canal a branche unique et double echantillonnage dans un systeme a banc de filtres. Cet egaliseur est evalue en complexite et performance et compare a l'egaliseur a 3 branches classique. Des estimations de nombres de coefficients simples sont proposes et verifiees par simulation. Elles mettent en evidence l'importance de certains parametres du systeme et particulierement du facteur d'arrondi du filtre de separation des sous-canaux. Dans la presentation des travaux, l'environnement ptolemy utilise dans les simulations est decrit brievement et le principe des transmissions multiporteuses existantes, l'ofdm, est rappele. Ensuite, les bancs de filtres utilises, filtres de synthese dans l'emetteur, d'analyse dans le recepteur, sont decrits, en detaillant les methodes de calcul des coefficients et en soulignant l'equivalence avec la decomposition en sous-bandes d'un signal et sa reconstruction. Pour l'egalisation des sous-canaux, l'egaliseur transversal a branche unique et double echantillonnage permet d'atteindre le meme niveau d'erreur residuelle que l'egaliseur transversal a 3 branches et echantillonnage critique. Au prix d'une complexite globale du systeme superieur, il apporte la robustesse au decalage des instants d'echantillonnage dans le recepteur. Les resultats presentes devraient aider les concepteurs de systemes multiporteuses a determiner la meilleure approche pour leur application et les guider dans les choix des parametres.
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Iwanesko, Marc. "Démembrement de propriété et techniques de transmission patrimoniale". Toulouse 1, 2010. http://www.theses.fr/2010TOU10083.
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La transmission optimale du patrimoine des parents à leurs descendants nécessite l'utilisation de divers outils juridiques : assurance-vie, régimes matrimoniaux, libéralités, sociétés, démembrements de propriété, notamment, sans omettre leurs corollaires fiscaux. Au premier rang de ces règles, figurent très certainement les démembrements de propriété et tout particulièrement l'usufruit. La volonté des parents de transmettre l'avoir, tout en conservant le pouvoir et les revenus, y trouve son aboutissement. La quasi-absence de textes d'ordre public confère à ce droit de jouissance sur la chose d'autrui, une étonnante plasticité, propre à une utilisation qui n'est limitée que par l'imagination. Pour autant, les règles civiles des démembrements de propriété posent de délicates questions, lorsqu'elles se confrontent au droit des sociétés et au droit fiscal, absents des préoccupations, tant des romains que du législateur de 1804The optimum transfer of property from parents to their descendants requires the use of a spectrum of legal tools including life insurance, matrimonial systems, gifts, companies, division of property, in addition to taw corollaries. Division of property is certainly at the forefront of these rules, especially where usufruct is concerned. This system is particularly well suited to parents who wish to transfer the enjoyment of an asset while retaining control of it, and income from it. The quasi-absence of public legislation in this respect gives the right of enjoyment of another person's property a surprising degree of plasticity, which lends itself well to usage that is limited only by the imagination. However, civil rules governing property division pose some complex questions, when they are confronted with company law and tax law, which were absent from the concerns both of the Romans and the law-makers of 1804
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El-Sayed, Ayman El-Sayed Ahmed. "Application-level multicast transmission techniques over the Internet". Grenoble INPG, 2004. http://www.theses.fr/2004INPG0021.
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Dans cette thèse, nous présentons une proposition pour établir un service Alternatif de communication de groupe qui déplace le support de multipoint depuis les routeurs vers les extrémités. Notre proposition, appelée HBM fonctionne au niveau applicatif et fournit un service efficace de distribution multipoint de données de type un-vers-plusieurs ou plusiers-vers-plusieurs. Avec cette approche les machines terminales, les serveurs et/ou des routeurs de bordure s'organisent automatiquement une topologie de distribution de recouvrement grâce à laquelle des données sont diffusées. Cette topologie de recouvrement peut se composer à la fois de connections point à point et de zones bénéficient d'un routage multicast natif (par exemple dans chaque site). Par conséquent elle offre un service de communication de groupe à tous les hôtes, même ceux situés dans un site qui n'a pas accès, une quelconque raison, au routage multicast natif. HBM est une solution centralisée, où tout, y compris la gestion d'adhésion de groupe et la création de topologie de recouvrement, est de la responsabilité d'un unique point de Rendez-vous (RP). Cette thèse se concentre sur trois aspects principaux : scalabilité, robustesse et sécurité. La scalabilité peut être en grande partie améliorée, avec quelques ajustements simples de certains paramètres de HBM tels la fréquence et la taille des messages de contrôle. La robustesse est un aspect pratique important, et nous présentons des techniques de réduction de pertes de paquet, tels l'addition des liens virtuels redundants qui évitent la partition de topologie en cas de panne d'un nœud de transit. Enfin nous étudions l'utilisation de HBM afin d'établir un service entièrement sécurisé mais efficace de communication de groupe entre plusieurs sites au moyen de VPN IPSec.
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Bejjani, Elie. "Techniques de transmission pour les canaux très dispersifs /". Paris : École nationale supérieure des télécommunications, 1998. http://catalogue.bnf.fr/ark:/12148/cb369953479.
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Kerlin, James Bernhard. "An investigation of modelling techniques for hybrid directional coupler design". Thesis, Queen's University Belfast, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356936.
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Chen, Wu-hsiang Jonas. "Error-resilient techniques for packet video communications /". Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/5850.
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Mitchinson, Ben. "Iterative kernel techniques in application to channel equalisation". Thesis, University of Sheffield, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269368.
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Jin, Jing. "RS-coded M-QAM transmission techniques for Wireless Communications". Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:8881/R/?func=dbin-jump-full&object_id=92363.
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Martin, Ian. "Practical error control techniques for transmission over noisy channels". Thesis, Lancaster University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287254.
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Edirisinghe, Sumuda G. "Dispersion compensation techniques in high bit rate transmission systems". Thesis, University of Essex, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343578.
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Fath, Thilo Christian Martin. "Evaluation of spectrally efficient indoor optical wireless transmission techniques". Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/8894.
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Optical wireless communications (OWC) has the potential to become a remedy for the shortage of the radio frequency (RF) spectrum. Especially in indoor environments, OWC could enable wireless home networking systems which offload data traffic from existing RF systems. In OWC, data is transmitted by modulating the intensity of light sources, typically incoherent light emitting diodes (LEDs). Thus, OWC systems employ intensity modulation (IM) and direct detection (DD) of the optical carrier. Since off-the-shelf LEDs have a limited modulation capability, the transmission bandwidth of practical OWC systems is restricted. Consequently, the available bandwidth has to be used efficiently. In this thesis, spectrally efficient optical wireless transmission techniques are evaluated. Firstly, multiple transmitter-receiver techniques are investigated. These multiple-input-multiple-output (MIMO) techniques provide high spectral efficiency, and therefore high data rates. Specifically, the MIMO techniques repetition coding (RC), spatial multiplexing (SMP) and spatial modulation (SM) are analysed for indoor OWC. The performance of these techniques is evaluated analytically and by means of computer simulations. It is shown that inducing power imbalance between the multiple optical transmitters can substantially improve the performance of optical MIMO techniques as the power imbalance improves the differentiability of the multiple channels. In addition, it is found that link blockage and the utilisation of transmitters having different optical wavelengths enhance channel differentiability as well. These methods enable the utilisation of optical MIMO techniques under conditions which typically disallow the application of MIMO schemes due to little differences between the multiple links. Secondly, a novel optical wireless transmitter concept is developed. This concept uses discrete power level stepping to generate intensity modulated optical signals, such as orthogonal frequency division multiplexing (OFDM) waveforms. The transmitter consists of several on-off-switchable LED groups which are individually controlled to emit scaled optical intensities. As a result, the digital-to-analogue conversion of the signals to be sent is done in the optical domain. This method enables the implementation of low-complex and power-efficient optical transmitter front-ends – the major shortcoming of conventional optical OFDM transmitters. Thirdly, a novel approach for wireless data transmission within an aircraft cabin is presented. The data is transferred by 2-dimensional visual code sequences. These sequences are displayed on the in-flight entertainment (IFE) screen and are captured by the built-in camera of a user device which acts as receiver. Transmission experiments within an aircraft cabin mock-up demonstrate the functionality of the implemented system under realistic conditions, such as ambient illumination and geometric configuration. Altogether, this thesis has analysed the potential of spectrally efficient optical wireless transmission techniques. It is shown that OWC systems can greatly benefit from these techniques.
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Abouseif, Akram. "Emerging DSP techniques for multi-core fiber transmission systems". Electronic Thesis or Diss., Institut polytechnique de Paris, 2020. http://www.theses.fr/2020IPPAT013.
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Les systèmes de communication optique ont connu plusieurs phases de développement au cours des dernières décennies. Ils approchent aujourd'hui les limites de capacité du cana non-linéaire. L'espace est aujourd'hui le dernier degré de liberté à mettre en œuvre afin de continuer à répondre aux demandes de capacité à venir pour les prochaines années. Par conséquent, des recherches intensives sont menées pour explorer tous les aspects concernant le déploiement du système de multiplexage par division spatiale (SDM). Plusieurs dégradations ont un impact sur les systèmes SDM en raison de l'interaction des canaux spatiaux qui dégrade les performances du système. Dans cette thèse, nous nous concentrons sur les fibres multicœurs (MCF) comme l'approche la plus prometteuse pour être le premier représentant du système SDM. Nous présentons différentes solutions numériques et optiques pour atténuer l'effet non unitaire connu sous le nom de perte dépendante du cœur (CDL). La première partie est consacrée à l'étude des performances de la transmission MCF en tenant compte des dégradations de propagation qui impactent les systèmes MCF. Nous proposons un modèle de canal qui aide à identifier le système MCF. La deuxième partie est consacrée à la technique optique pour améliorer les performances de transmission avec une solution optimale pour la réduction des CDL. Ensuite, nous avons introduit des techniques numériques pour des améliorations supplémentaires, la pré-compensation Zero Forcing et le codage spatio-temporel pour une atténuation CDL supplémentaire. Tous les résultats de simulation sont validés analytiquement en dérivant les bornes supérieures de probabilité d'erreurOptical communication systems have seen several phases in the last decades. It is predictable that the optical systems as we know will reach the non-linear capacity limits. At the moment, the space is the last degree of freedom to be implemented in order to keep delivering the upcoming capacity demands for the next years. Therefore, intensive researches are conducted to explore all the aspects concerning the deployment of the space-division multiplexing (SDM) system. Several impairments impact the SDM systems as a result from the interaction of the spatial channels which degrades the system performance. In this thesis, we focus on the multi-core fibers (MCFs) as the most promising approach to be the first representative of the SDM system. We present different digital and optical solutions to mitigate the non-unitary effect known as the core dependent loss (CDL). The first part is dedicated to study the performance of the MCF transmission taking into account the propagating impairments that impact the MCF systems. We propose a channel model that helps to identify the MCFs system. The second part is devoted to optical technique to enhance the transmission performance with an optimal solution. After, we introduced digital techniques for further enhancement, the Zero Forcing pre-compensation and the space-time coding for further CDL mitigation. All the simulation results are validated analytically by deriving the error probability upper bounds
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Murray, Neil. "Advanced techniques for the improvement of optical transmission systems". Thesis, Aston University, 2014. http://publications.aston.ac.uk/23418/.
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This thesis presents the experimental investigation into two novel techniques which can be incorporated into current optical systems. These techniques have the capability to improve the performance of transmission and the recovery of the transmitted signal at the receiver. The experimental objectives are described and the results for each technique are presented in two sections: The first experimental section is on work related to Ultra-long Raman Fibre lasers (ULRFLs). The fibre lasers have become an important research topic in recent years due to the significant improvement they give over lumped Raman amplification and their potential use in the development of system with large bandwidths and very low losses. The experiments involved the use of ASK and DPSK modulation types over a distance of 240km and DPSK over a distance of 320km. These results are compared to the current state of-the-art and against other types of ultra-long transmission amplification techniques. The second technique investigated involves asymmetrical, or offset, filtering. This technique is important because it deals with the strong filtering regimes that are a part of optical systems and networks in modern high-speed communications. It allows the improvement of the received signal by offsetting the central frequency of a filter after the output of a Delay Line Interferometer (DLI), which induces significant improvement in BER and/or Qvalues at the receiver and therefore an increase in signal quality. The experimental results are then concluded against the objectives of the experimental work and potential future work discussed.
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Haidar, Ibrahim. "Digital code division multiplex techniques for data transmission applications". Thesis, Aston University, 1985. http://publications.aston.ac.uk/8052/.
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Moebus-Bergeron, Susanne. "Tooling techniques in Romanesque illumination: appearance, transmission, and implications". Thesis, Boston University, 2013. https://hdl.handle.net/2144/12823.
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Contains two volumes. Thesis (Ph.D.)--Boston University
PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.This dissertation offers proof that tooling was not a new phenomenon of thirteenth century Gothic illumination, as has up until now generally been believed, but was part of a well established technical tradition in twelfth century manuscript decoration. Gold surfaces are tooled with metal instruments in as many as filly-six extant manuscripts illuminated between 1125 and 1200 in French, English, and German workshops. These manuscripts show that Romanesque illuminators employed a variety of techniques to embellish gold grounds and other metallic surfaces with an assortment of ornamental patterns that range from simple dot clusters to elaborate foliate, diaper, and checkerboard designs. This is the first study to systematically examine tooling techniques and their relationship with gilding procedures in twelfth century manuscripts. This technical approach, combined with analysis of the decoration of relevant manuscripts, opens new insights about the initiation of tooling in medieval illumination, the working methods of twelfth century illuminators, and the contribution of individual artists to the conceptualization of manuscript decoration. In addition, the data collected in this study provides new evidence relevant to broader issues in Romanesque art, namely the meaning of gold grounds in manuscript decoration, the interrelationship of the arts, the artistic exchange across national boundaries, and the transmission of Byzantine features to twelfth century Western illumination. Aside from service books, manuscript examples include copies of patristic, early medieval, scholastic, and pagan texts, in which tooling was used to enhance the visual appeal of gold surfaces to a monastic audience. These manuscripts provide evidence that French and English illuminators used punches fashioned for the blind-tooling of leather bindings which has been dismissed in previous scholarship on punch marks in painting. Hildesheim illuminators borrowed punches from the local bronze casting workshop. Tooling has also proven useful in tracing the careers of individual illuminators, such as the Lambeth Master, and their movements across national borders. This study on the development of tooling in twelfth century illumination thus provides important new evidence that, it is hoped, will make a significant contribution to our general understanding of Romanesque art.
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Appert, Damien. "Conception et évaluation de techniques d'interaction non visuelle optimisées pour de la transmission d'information". Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30095/document.
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Dans des situations où la perception visuelle est fortement contrainte ou déficiente, il est nécessaire de rendre perceptible l'information dans une modalité non visuelle, tout en prenant en compte des capacités sensorielles et mnésiques humaines. Par exemple, un non-voyant, souhaitant prendre connaissance d'un itinéraire, devra le parcourir de façon non visuelle et le mémoriser. Cependant, outre l'aspect matériel, la mise en œuvre de solutions alternatives (non visuelles) demeure confrontée aux capacités cognitives de l'utilisateur (compréhension, mémorisation, intégration de plusieurs informations, etc.). L'objet de cette thèse est de contribuer à la conception de techniques d'interactions permettant d'optimiser la transmission non visuelle d'informations. A ces fins, j'ai exploré l'apport de la multimodalité comme moyen d'optimisation permettant d'outrepasser les limites de la mémorisation. Je me suis concentré sur l'étude des techniques d'interaction basées sur les modalités auditives et tactiles, en limitant au maximum l'utilisation de la parole, afin de concevoir des techniques pour des environnements différents (flexibilité), d'optimiser l'utilisation de canaux perceptifs (exploitation des propriétés du son dans des messages audio pour transmettre plus d'informations, par exemple), d'éviter de limiter mes techniques par la barrière de la langue ou de sa compréhension et enfin, pour explorer d'autres solutions que la synthèse vocale seule. Les travaux de ma thèse ont mené à la conception, à l'implémentation et à l'évaluation de techniques d'interaction multimodale non visuelle, en réponse à différents contextes, dont, en particulier, ceux de la transmission d'informations de type , (couple de coordonnées) et (séquence de couples direction-distance). Pour parvenir à concevoir mes interactions, j'ai, tout d'abord, effectué une revue de la littérature, afin d'en extraire les principaux facteurs de conception de techniques d'interaction dédiées à la transmission non visuelle d'information. Puis, j'ai organisé ces facteurs sous la forme d'un cadre d'analyse, sur lequel je me suis appuyé pour concevoir chacune de mes techniques. Trois expériences distinctes ont permis d'évaluer l'influence de facteurs de conception sur l'efficacité des interactions et la satisfaction des utilisateurs vis-à-vis des techniques. Je peux, notamment, citer l'implication des utilisateurs (actif ou passif), la présence d'aides explicites", la transmission de plusieurs informations en parallèle et la modalité principale utilisée et, le type de codage dans lequel est encodée l'informationIn situations where the visual perception is strongly constraint or deficient, it is necessary to make perceptible the information with a "not visual form" while taking into account human sensory and mnesic capacities. For example, a blind person wishing to acquaint an itinerary must read it under a non visual form and memorize it. However, besides the material aspect, the implementation of alternatives (non-visual) still faces to the cognitive abilities of the user (comprehension, memorization, integration of various information, etc.). The purpose of this thesis is to contribute to the design of interaction techniques allowing to optimize the transmission not visual of the information. For these purposes, I explored the feature of multimodality as a means of optimization, allowing of exceeding the memorization limits. I focused on the study of interaction techniques based on auditory and tactile modalities and by minimizing the use of the speech, in order to develop techniques for different environments (flexibility), optimize the use of perceptual channels (operating the properties of sound in audio messages to transmit more information, for example), avoid limiting my techniques by the language barrier or understanding and finally, to explore alternatives to the synthesised voice alone. The works of my thesis led to the design, to the implementation and to the evaluation of interaction techniques "non-visual" and "multiform", in answer to different contexts, whom in particular those of the information transmission of type , (pair of coordinates) and (sequence of couples direction-distance). To achieve design my interactions, I have made a review of literature in order to extract the main factors of design of interaction techniques dedicated to the transmission not visual of the information. Then, I have organized these factors in an analytical framework on which I have relied to design each of my techniques. Three separate experiments were led to evaluate the influence of design factors on the effectiveness of interactions and satisfaction towards users of technology. I can give some of them, the involvement of users (active or passive), the presence of explicit help, the transmission of several information in parallel, the main modality used and the type of coding in which is encoded the information
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Thorlby, J. Paul. "Equalisation techniques for coded modulation". Thesis, University of York, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338549.
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Fu, Wing Ming. "An investigation into real time modelling techniques for power system fault transients". Thesis, University of Bath, 1992. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306762.
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Witwit, Abdul-Mehdi Rahim Mohammed. "Meshing techniques for TLM diffusion problems". Thesis, University of Hull, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296281.
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Lim, Wee Shoong. "An evaluation of management techniques for SONET/SDH Telecommunication networks". Thesis, Monterey California. Naval Postgraduate School, 2004. http://hdl.handle.net/10945/1389.
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Approved for public release; distribution is unlimitedA study of SONET network management applications and the load they impart to the network is conducted to provide a better understanding of the capability of various management approaches. In this study, a SONET network is set up in the Advanced Networking Laboratory of the Naval Postgraduate School using four Cisco ONS 15454s. Next, two Element Management Systems, the Cisco Transport Controller and the Cisco Transport Manager, are deployed onto the SONET network. Subsequently, the network traffic of the Element Management Systems is captured and analyzed using a packet analyzer. Link utilization of the two tools is computed using the first-order statistics of the captured traffic distributions. In addition, the Hurst parameter is estimated using the variance-index plot technique (which uses higher-orders statistics of the modeled distributions) to determine the captured traffic's degree of self-similarity. Finally, the calculated utilization is extrapolated to obtain the link utilization for 2500 network elements (the maximum number supported by the Cisco Transport Manager). The result obtained is useful in determining the maximum number of network elements (Cisco ONS 15454s) that the Cisco Transport Manager can support from a network loading point of view.
Civilian, Ministry of Defense, Singapore
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Rajendra, S. "Travelling-wave techniques applied to the protection of teed circuits". Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355029.
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Lee, Hyungkeun. "Efficient techniques for multimedia transmission over packet-switched cellular networks". Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2002. http://wwwlib.umi.com/cr/syr/main.
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Beg, Mirza S. "Novel detection techniques for data transmission over a fading channel". Thesis, Loughborough University, 1990. https://dspace.lboro.ac.uk/2134/27493.
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This thesis describes new techniques of detection and fast start-up channel estimation for transmitting digital data over a fast 'frequency-selective' fading channel of the type encountered in fading mobile communications. The model of the channel involves a large number of reflected signals delayed in time by different amounts and reaching the receiver via different paths, each of which is represented by an independent Rayleigh fading channel. Such a model gives rise to frequency-selective fading and an appreciable degree of intersymbol interference. Base bend representation of the quadrature amplitude modulated data transmission system is first studied.
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Chin, Craig. "Multilevel data compression techniques for transmission of audio over networks". FIU Digital Commons, 2001. http://digitalcommons.fiu.edu/etd/2336.
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With the spread of the Internet into mainstream society, there has come a demand for the efficient transmission of multimedia information. Accompanying the drive to find more efficient ways of utilizing limited transmission bandwidth is a need to find novel ways of compressing data. This thesis proposed the utilization of transform coding compression techniques for the transmission of audio data across networks. The Discrete Cosine Transform (DCT) and the Discrete Sine Transform (DST) were the primary transforms utilized. This thesis investigated the viability of utilizing individual transforms, as well as, nested modifications of these transforms for compression purposes. These techniques were compared to those already in existence. Viability was determined using objective compression measures. It was found that transform coding techniques gave a useful alternative to the techniques in existence. A voice-over-IP (VOIP) application that utilized one of the transform coding techniques was implemented.
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Muqattash, Alaa Hilal. "Medium Access Control and Adaptive Transmission Techniques in Wireless Networks". Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1359%5F1%5Fm.pdf&type=application/pdf.
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Choong, Yew Kwan. "Advanced modal expansion techniques for the transmission line modelling method". Thesis, University of Nottingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403698.
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Johnston, Alan Biggar. "Investigation of magnetic microstructures using novel transmission electron microscopy techniques". Thesis, University of Glasgow, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294166.
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Liga, G. "Digital techniques for ultra-high data rate optical fibre transmission". Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/1570380/.
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The exponential growth of the demand for higher data rates is pushing scientists to find ways to improve the internet infrastructure, which crucially relies on optical fibres. The main obstacle to increasing transmission rates of optical fibre systems is presented by the fibre Kerr nonlinear effect, which impairs signal transmission as the transmitted power is increased. Fortunately, optical coherent detection, in combination with digital signal processing techniques, have enabled more sophisticated digital receivers, tailored to the optical fibre channel. This thesis describes a comprehensive study on the performance of two digital receiver-side techniques: digital back-propagation (DBP) and maximum likelihood sequence detection (MLSD). DBP is the most widespread digital technique to mitigate fibre nonlinearity at the receiver. The performance of DBP, is assessed for long-haul, wide-bandwidth systems, highlighting theoretical gains and practical limitations. Analytical models to predict DBP performance are discussed and compared to numerical results. The impact of polarisation-mode dispersion on the capability of DBP to remove nonlinear impairments is investigated. The principles of detection theory are discussed in the context of the optical fibre nonlinear channel. Following such principles, MLSD strategies are studied and their performance analysed for unrepeatered systems. A close to optimum receiver scheme, using the Viterbi algorithm, is proposed and investigated for the first time in a singlespan fibre system. Finally, information-theoretic tools are used to predict achievable information rates of both receiver schemes, when employed in combination with forward error correction codes. In particular, pragmatic coded modulation schemes were examined to assess the potential of off-the-shelf channel codes. Both receiving strategies analysed were demonstrated to significantly outperform conventional receivers optimised for the additive white Gaussian noise channel. The results of this thesis provide a useful insight on the properties of the optical fibre channel and on the design of receivers aiming to maximise information rates through it.
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Hicheri, Nizar. "Approche unifiée des techniques de transmission radio sur voie descendante". Paris, CNAM, 2004. http://www.theses.fr/2004CNAM0473.
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Cette thèse présente tout d'abord un formalisme matriciel qui permet de représenter les approches DS-CDMA, MC-CDMA et OFDM de manière unifiée. On montre ainsi dans un premier temps que si l'on cherche des séquences d'étalement DS-CDMA qui sont orthogonales et dont l'orthogonalité résiste à une imprécision temporelle d'un élément de la séquence alors, obligatoirement, ces séquences sont les exponentielles complexes de Fourier. Une fois les formes d'ondes exprimées et les récepteurs développés, on s'intéresse aux performances comparées de ces différentes approches sur plusieurs canaux de propagation. Les trois formes d'onde donnent pour un contexte de voie descendante d'un système de radiocommunications des performances très similaires. On a ensuite introduit une nouvelle stratégie DS-CDMA appelée « Waterfilling CDMA ». Nous construisons ainsi une famille de séquences qui prennent en compte les caractéristiques du canalThis thesis presents first of all a matrix formalism that allows representing the DS-CDMA, MC-CDMA and OFDM approaches in a unified way. The formalism allows putting in light several basic results in very quick manner. We show thus if one looks for spreading orthogonal DS-CDMA sequences which stays orthogonal even with a temporal imprecision of one sequence element then, necessarily, these sequences are the complexes exponential of Fourier. Once waves form expressed and the receivers developed. We interested in compared performances of these different approaches on several channels propagation. In final, it appears that, outside material simplifications of a receiver in comparison with the other, the three wave forms give, for a downlink system radio-communications context, very similar performances. The formalism introduced in this thesis allows developing a new strategy of CDMA called in these works "Waterfilling CDMA". It is showed that in the same manner that the cyclic prefix can be used with profit in DS-CDMA, the waterfilling also can be used in this context. Thus we construct a spreading sequences family that take into account the channel characteristics
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Kazerooni, Ali Khajeh. "Methodologies and techniques for transmission planning under corrective control paradigm". Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/methodologies-and-techniques-for-transmission-planning-under-corrective-control-paradigm(16d20003-4175-4405-8d9f-78fb7b138c88).html.
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Environmental concerns and long term energy security are the key drivers behind most current electric energy policies whose primary aim is to achieve a sustainable, reliable and affordable energy system. In a bid to achieve these aims many changes have been taking place in most power systems such as emergence of new low carbon generation technologies, structural changes of power system and introduction of competition and choice in electricity supply. As a result of these changes, the level of uncertainties is growing especially on generation side where the locations and available capacities of the future generators are not quite clear-cut. The transmission network needs to be flexibly and economically robust against all these uncertainties. The traditional operation of the network under preventive control mode is an inflexible practice which increases the total system cost. Corrective control operation strategy, however, can be alternatively used to boost the flexibility, to expedite the integration of the new generators and to decrease the overall cost. In this thesis, the main focus is on development of new techniques and methodologies that can be used for modelling and solving a transmission planning problem under the assumption that post-contingency corrective actions are plausible. Three different corrective actions, namely substation switching, demand response and generation re-dispatch are investigated in this thesis. An innovative multi-layer procedure deploying a genetic algorithm is proposed to calculate the required transmission capacity while substation switching is deployed correctively to eradicate the post-fault network violations. By using the proposed approach, a numerical study shows that the network investment reduces by 6.36% in the IEEE 24 bus test system. In another original study, generation re-dispatch corrective action is incorporated into the transmission planning problem. The ramp-rate constraints of generators are taken into account so that the network may be overloaded up to its short-term thermal rating while the generation re-dispatch action is undertaken. The results show that the required network investment for the modified IEEE 24 bus test system can be reduced by 23.8% if post-fault generation re-dispatch is deployed. Furthermore, a new recursive algorithm is proposed to study the effect of price responsive demands and peak-shifting on transmission planning. The results of a study case show that 7.8% of total investment can be deferred. In an additional study on demand response, a new probabilistic approach is introduced for transmission planning in a system where direct load curtailment can be used for either balancing mechanism or alleviating the network violations. In addition, the effect of uncertainties such as wind power fluctuation and CO2 emission price volatility are taken into account by using Monte Carlo simulation and Hypercube sampling techniques. Last but not least, a probabilistic model for dynamic thermal ratings of transmission lines is proposed, using past meteorological data. The seasonal correlations between wind power and thermal ratings are also calculated. £26.7 M is the expected annual benefit by using dynamic thermal ratings of part of National Grid's transmission network.
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Joshi, Vilas (Vilas Vishwanath) Carleton University Dissertation Engineering Electrical. "Sequence estimation techniques for enhanced digital subscriber loop transmission capability". Ottawa, 1988.
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Karupongsiri, Chalakorn. "QoS Techniques for Smart Meter Packets Transmission on LTE Networks". Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/16453.
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The Smart Grid (SG) is defined as an intelligent electricity delivery system. It is a modern electric power that improves efficiency, reliability and sustainability of electricity services such as remote meter reading, diagnoses problems, and unauthorized customer detection. Although the native version of power grid is monitored and controlled by Supervisory Control and Data Acquisition (SCADA) system, it is implemented only at high voltage transmission. The SCADA does not cover all parts of the power grid. The SG consists of generation, transmission, distribution, and electricity consumption. All components of the SG architecture can be monitored and controlled via communication links. Smart Meter (SM) is a critical component of the Advanced Metering Infrastructure (AMI) that collects power consumption information from customer and reports it to the SG control centre. The SM is a Machine-to-Machine (M2M) communication that works without human operation. Typically there are number of SMs overloading it with billions of tiny fixed size packets containing power consumption data. All SMs need to establish a connection to transmit SM packets. The Long-Term Evolution (LTE) network has become an attractive candidate for SG communications. In spite of LTE’s growing popularity as a means of transporting SG data, it was primarily designed for high speed and high capacity mobile data traffic such as video streaming and Internet involving Human-to-Human (H2H) communication. The LTE standard can offer a huge number of SM connection. However, deploying SMs on LTE network increases the packet loss, packet delay and re-establishment as the SMs needs to access the network within a given time interval to send a small packet. This degrades the performance of the LTE network. In addition, the SM packets should be given a priority as the packets are used for power outage monitoring. Five mechanisms of the state-of-art LTE network are currently used during an overload issue such as: 1) Backoff indication; 2) Slotted access; 3) Access Class Barring; 4) Pull-based scheme; 5) Dynamic allocation of RACH resource scheme. Although these mechanisms can overcome, the issue to certain extent they increase access delay. In order to overcome this issue, this thesis introduces a Quality of Service (QoS) mechanism for the SM packets on the LTE network: 1) The uplink scheduling for SM transmission guarantees SM packet connection so that all SMs can successfully access the network. The key contribution of the proposed method is the Admission Control (AC) that controls all connections to access the eNode-B and uplink scheduling for SM queuing management; 2) In order to reduce the use of preamble signatures, SM packets are transmitted via Tracking Area Update (TAU) packet that is carried on Non-Access Stratum (NAS) message. This proposed technique can reduce preamble usage and resource consumption at the eNode-B; 3) Preamble collision issue is solved by a combination of contention and non-contention based random access procedure mechanisms. Initially, SM sends the preamble index on the contention based. If the initial access collides, then a new preamble index is given to the conflicting SM by eNode-B. With the proposed model, although SM packets are sent into network by interval time, it need not reserve the preamble for SMs at the eNode-B. The simulation results are verified by mathematical analysis. The analytical model differs with simulation result approximately 2%; and 4) LTE network performance is increased by combination of contention and non-contention based methods are combined with SM packets transmission via TAU method. The results shows the efficiency of the model in terms of lower packet delay, reduced number of packet loss, and reduced re-establishment attempts. The simulations are performed on a SM packet communication scenario. In practice, the proposed method can be applied for H2H communication at places with high intensity of smart phone connections that needs preamble signatures and causes congestions, for example stadiums, halls and outdoor events.
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Baracca, Paolo. "Transmission Techniques and Resource Allocation in Coordinated Multi-Point Systems". Doctoral thesis, Università degli studi di Padova, 2012. http://hdl.handle.net/11577/3422562.
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This thesis is focused on the design of transmission schemes and resource allocation algorithms for both downlink and uplink of coordinated multi-point (CoMP) systems.
In current cellular systems, which employ a full frequency reuse of the spectral resource, interference has been recognized as one of the most limiting factor: in particular, user equipments (UEs) close to the cell edge typically suffer strong inter-cell interference (ICI). This interference, which is due to the transmission of neighbouring base stations (BSs) in the downlink and UEs in neighbouring cells in the uplink, limits the fairness across the UEs and, in general, the overall system performance. It has been shown that BS coordination is able to dramatically improve the system performance with respect to non-cooperative schemes by limiting the impact of ICI. Coordination is obtained by sharing among the BSs channel state information (CSI), data to be sent to the UEs in the downlink and signals received by the BSs in the uplink. However, BS coordination also poses several new challenges. First of all, the backhaul may not be able to support the sharing among the BSs of all the data to be sent to the UEs or signals received by BSs. Moreover, obtaining reliable CSI at the BSs for all the UEs in the network may be an issue because of a) limited bandwidth available for the feedback channel in frequency division duplex (FDD) systems and b) noise on channel estimation in time division duplex (TDD) systems. Thereby, it is crucial to develop practical algorithms that deal efficiently with both of these issues in order to achieve, in a realistic scenario, the performance gain enabled by cooperation.
This thesis is basically divided into two parts. In the first part we focus on downlink CoMP systems and we provide four main contributions. First, we propose a novel transmission scheme based on linear precoding and quantization of quadrature amplitude modulation (QAM) constellations. With the aim of reducing the backhaul occupation, a set of cooperative BSs transmit toward the UE a quantized version of the QAM symbol by using a joint precoder, while the serving BS transmits a quantization error symbol. In order to avoid modifications of the receiver, we impose that the combination of the two symbols through the channels yields at the UE the original QAM symbol. Numerical results show that this approach ensures a network spectral efficiency close to a theoretical limit obtained by using the more complex Slepian-Wolf encoding. Secondly, we develop a greedy dynamic algorithm to jointly organize BSs in clusters and to schedule UEs in each cluster. A considerable gain is achieved by the proposed approach with respect to both non-cooperative schemes and static clustering. Thirdly, we focus on the feedback design in FDD systems and we consider a practical strategy where each UE quantizes the CSI by using codebooks designed for a single-cell scenario. We propose two algorithms which allow the UE to a) select a subset of preferred BSs and b) optimize the number of feedback bits allocated to the quantization of each CSI. In particular, more feedback bits are sent to BSs with stronger signals. Finally, we adapt our scheme based on QAM quantization to a different scenario where a set of relays assists the transmission of a BS toward a UE. In such a case, the proposed joint precoding is employed by the relays to serve the UE, whereas the links connecting the relays to the BS represent the backhaul infrastructure.
In the second part of the thesis, we consider the uplink of CoMP systems by assuming that UEs transmit toward BSs by using single carrier frequency division multiple access (SC-FDMA), which is the modulation employed in the uplink of Long Term Evolution (LTE). In this scenario, we propose a new scheduler of the signals exchanged among BSs on the backhaul that allows each BS to share only a subset of the subcarriers of each SC-FDMA block.Questa tesi è incentrata sullo studio di schemi di trasmissione e algoritmi per l’allocazione di risorse sia per il downlink che per l’uplink di sistemi CoMP. Nei sistemi cellulari odierni, in cui vi è un riutilizzo delle stesse frequenze in ogni cella, l’interferenza inter-cella rappresenta uno dei fattori più limitanti andando a ridurre sensibilmente l’efficienza spettrale degli utenti a bordo cella. Questa interferenza, che è dovuta nel downlink alla trasmissione da parte di stazioni radio base in celle vicine e nell’uplink alla trasmissione di utenti in celle vicine, limita la fairness tra gli utenti e, più in generale, le prestazioni del sistema. Tuttavia, la coordinazione tra stazioni radio base è in grado di limitare l’impatto dell’interferenza inter-cella e migliorare notevolmente le prestazioni rispetto ai sistemi senza cooperazione. La coordinazione prevede la condivisione tra stazioni radio base di informazioni sui canali, dei dati da trasmettere agli utenti nel downlink e dei segnali ricevuti dalle stazioni radio base nell’uplink. L’implementazione pratica della coordinazione pone però molte nuove problematiche. Prima di tutto, l’infrastruttura di backhaul può non essere in grado di supportare la condivisione di dati e segnali tra le stazioni radio base. Inoltre, può essere difficile ottenere una conoscenza affidabile dei canali tra un utente e le stazioni radio base nella rete a) per una banda limitata dedicata al canale di feedback in sistemi a divisione di frequenza e b) per il rumore sulla stima di canale in sistemi a divisione di tempo. Di conseguenza, è importante sviluppare degli algoritmi pratici che tengano in considerazione queste problematiche e mantengano in un sistema reale il guadagno garantito dalla coordinazione. Questa tesi è divisa in due parti. La prima parte è incentrata sul downlink e vengono forniti quattro contributi principali. In primo luogo, si propone un nuovo schema di trasmissione che si basa sul precoding lineare e la quantizzazione di costellazioni QAM. Con l’obiettivo di ridurre il traffico sulla rete di backhaul, un insieme di stazioni radio base coordinate trasmette verso un utente un simbolo che è una versione quantizzata del simbolo QAM originale, mentre la stazione radio base servente trasmette una versione scalata dell’errore di quantizzazione. Imponendo che la combinazione dei due campioni al ricevitore dia il simbolo QAM originale, lo schema proposto non richiede alcuna modifica al lato utente. I risultati numerici mostrano che l’efficienza spettrale ottenuta con questa tecnica si avvicina a quella ottenuta utilizzando la più complicata codifica di Slepian-Wolf. In secondo luogo, si propone un algoritmo greedy dinamico di scheduling e clustering per organizzare le stazioni radio base in cluster e per scegliere gli utenti serviti da ciascun cluster. Un guadagno considerevole è ottenuto grazie al metodo proposto rispetto a schemi senza cooperazione e schemi con clustering statico. In terzo luogo, viene studiato il problema del feedback per sistemi a divisione di frequenza e si considera uno schema pratico dove l’utente quantizza i canali utilizzando dei codebook disegnati per sistemi senza coordinazione. Con questo schema si propongono due algoritmi che permettono all’utente di a) selezionare l’insieme preferito di stazioni radio base e b) ottimizzare il numero di bit utilizzati per quantizzare ciascun canale. Nel dettaglio, questi algoritmi allocano più bit per la quantizzazione dei canali più forti. Infine, si adatta lo schema che si basa sulla quantizzazione di costellazioni QAM ad uno scenario dove un insieme di relay assiste la trasmissione di una stazione radio base verso un utente. In questo caso lo schema di precoding è utilizzato dai relay per servire l’utente, mentre i link che connettono i relay alla stazione radio base rappresentano il backhaul. Nella seconda parte della tesi si considera l’uplink di sistemi CoMP e si assume che gli utenti trasmettano verso le stazioni radio base utilizzando la modulazione SC-FDMA, che è lo schema utilizzato in LTE. Per questo scenario, si propone un nuovo scheduler dei segnali scambiati sul backhaul tra stazioni radio base che consente ad ogni stazione di condividere solo un sottoinsieme delle sottoportanti di ciascun blocco SC-FDMA.
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Zhou, Yiqing, e 周一靑. "Advanced techniques for high speed wireless communications". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B29296080.
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Chebbo, Hind Munzer. "Power transmission planning using heuristic optimisation techniques : deterministic crowding genetic algorithms and ant colony search methods". Thesis, Brunel University, 2000. http://bura.brunel.ac.uk/handle/2438/5781.
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The goal of transmission planning in electric power systems is a robust network which is economical, reliable, and in harmony with its environment taking into account the inherent uncertainties. For reasons of practicality, transmission planners have normally taken an incremental approach and tended to evaluate a relatively small number of expansion alternatives over a relatively short time horizon. In this thesis, two new planning methodologies namely the Deterministic Crowding Genetic Algorithm and the Ant Colony System are applied to solve the long term transmission planning problem. Both optimisation techniques consider a 'green field' approach, and are not constrained by the existing network design. They both identify the optimal transmission network over an extended time horizon based only on the expected pattern of electricity demand and generation sources. Two computer codes have been developed. An initial comparative investigation of the application of Ant Colony Optimisation and a Genetic Algorithm to an artificial test problem has been undertaken. It was found that both approaches were comparable for the artificial test problem.
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Wu, Qing, e 吳慶. "Object-based coding and transmission for plenoptic videos". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B39634279.
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Tabisz, Wojciech Antoni. "High-frequency multi-resonant power conversion techniques". Diss., Virginia Tech, 1990. http://hdl.handle.net/10919/37404.
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Jia, Jundi. "Transmission Expansion Planning in Large Power SystemsUsing Power System Equivalencing Techniques". Thesis, KTH, Elektriska energisystem, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-149679.
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With an increasing demand for electric power, new transmission lines should be constructed with a rational plan in the long run to guarantee a reliable and economic operation. The transmission expansion planning (TEP) is a mixed integer non-linear programming (MINLP) optimization problem in nature, which requires tremendous computational efforts especially when it comes to a large-scale power system. Although a diversity of simplifications and computational techniques has been applied to TEP, it is still challenging to derive an optimal plan within little simulation time. Since equivalencing technique is able to reduce the size of a large-scale power system and help achieve remarkable computational performance, it is possibly effective and efficient to handle the intrinsic complexity of TEP problem. In this thesis, based on a detailed literature review, a mixed integer linear programming (MILP) approach in DC model is firstly formulated for a dynamic TEP problem considering N – 1 security criterion. Then, two traditional power flow based equivalencing techniques that are appropriate for simplifying TEP, REI and WARD, with necessary modifications, are respectively implemented in the initial TEP problem. The proposed algorithms are simulated on IEEE 24-bus reliability test system (RTS) to compare optimal plans between the original and equivalent system. Further assumptions and adjustments are searched and tested to get more accurate optimal plans. The results show that both modified equivalencing techniques can significantly decrease the simulation time. Regarding IEEE 24-bus RTS, the proposed algorithm for modified REI method can achieve relatively precise optimal plan with few errors while modified WARD method is not as good as modified REI method. Therefore, the modified REI method has a potential to be implemented in TEP problem to reduce the complexity and computational effort for large power system without jeopardizing accuracy. Further studies are needed to tune the modified REI method and revise the obtained optimal plan.