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Dissertations / Theses on the topic 'Digital transmission'
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1
Caldwell, Niall James. "Digital Displacement hydrostatic transmission systems." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/27735.
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Digital Displacement pumps and motors are a new type of hydraulic machine, in which fluid commutation and displacement control are achieved by solenoid actuated valves under the command of a microprocessor, rather than mechanical means. The thesis is that radial piston machines, built according to this principle, offer energy efficiency and control advantages over variable stroke axial piston pumps, when applied to hydrostatic vehicle transmissions. Experimental results on the efficiency of prototypes are analysed and compared to published results from swashplate machines, showing an improvement in energy efficiency. Loss models are proposed and compared with experiment. A Digital Displacement motor suitable for propelling a vehicle is described and the design and development of the mechanics, electro-magnetics and embedded software are described. Experimental results are also presented, illustrating the performance of a demonstrator vehicle driven by the motor, in particular demonstrating the closed-loop regulation of vehicle speed using motor displacement control. A demonstrator vehicle is described which features a hydrostatic transmission using both a Digital Displacement pump and an axial piston motor. Experimental results of pump performance are presented with specific focus on vehicle propel. A control technique is described which increases the sensitivity of the pump at low speeds. Results are presented of tests on the prototype transmission system, focussing on the time-domain system dynamics. A computer simulation model of the vehicle is presented and results compared to experiment.
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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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He, Wei. "Adaptive-rate digital speech transmission." Thesis, University of Warwick, 1993. http://wrap.warwick.ac.uk/104723/.
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Moore, Philip John. "Adaptive digital distance protection." Thesis, City University London, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328244.
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Wu, Kuang-Tsan. "On spectrally efficient digital transmission systems." Thesis, University of Ottawa (Canada), 1986. http://hdl.handle.net/10393/5408.
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Wang, Li. "TDMA digital mobile radio transmission system." Thesis, University of Liverpool, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240335.
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Zammit, Saviour. "Digital video transmission over wireless networks." Thesis, Aston University, 1995. http://publications.aston.ac.uk/8058/.
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The advent of the Integrated Services Digital Network (ISDN) led to the standardisation of the first video codecs for interpersonal video communications, followed closely by the development of standards for the compression, storage and distribution of digital video in the PC environment, mainly targeted at CD-ROM storage. At the same time the second-generation digital wireless networks, and the third-generation networks being developed, have enough bandwidth to support digital video services. The radio propagation medium is a difficult environment in which to deploy low bit error rate, real time services such as video. The video coding standards designed for ISDN and storage applications, were targeted at low bit error rate levels, orders of magnitude lower than the typical bit error rates experienced on wireless networks. This thesis is concerned with the transmission of digital, compressed video over wireless networks. It investigates the behaviour of motion compensated, hybrid interframe DPCM/DCT video coding algorithms, which form the basis of current coding algorithms, in the presence of high bit error rates commonly found on digital wireless networks. A group of video codecs, based on the ITU-T H.261 standard, are developed which are robust to the burst errors experienced on radio channels. The radio link is simulated at low level, to generate typical error files that closely model real world situations, in a Rayleigh fading environment perturbed by co-channel interference, and on frequency selective channels which introduce inter symbol interference. Typical anti-multipath techniques, such as antenna diversity, are deployed to mitigate the effects of the channel. Link layer error control techniques are also investigated.
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Han, Yu. "Optimization of Modulation Constrained Digital Transmission Systems." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37097.
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The regular waterfilling(WF) policy maximizes the mutual information of parallel channels, when the inputs are Gaussian. However, Gaussian input is ideal, which does not exist in reality. Discrete constellations are usually used instead, such as $ M $-PAM and $ M $-QAM. As a result, the mercury/waterfilling (MWF) policy is introduced, which is a generalization of the regular WF. The MWF applies to inputs with arbitrary distributions, while the regular WF only applies to Gaussian inputs. The MWF-based optimal power allocation (OPA) is presented, for which an algorithm called the internal/external bisection method is introduced.
The constellation-constrained capacity is discussed in the thesis, where explicit expressions are presented. The expression contains an integral, which does not have a closed-form solution. However, it can be evaluated via the Monte Carlo method. An approximation of the constellation-constrained capacity based on the sphere packing method is introduced, whose OPA is a convex optimization problem. The CVX was used initially, but it did not generate satisfactory results. Therefore, the bisection method is used instead.
Capacities of the MWF and its sphere packing approximation are evaluated for various cases, and compared with each other. It turns out the sphere packing approximation has similar performances to the MWF, which validates the approximation. Unlike the MWF, the sphere packing approximation does not suffer from the loss of precision due to the structure of MMSE functions, which demonstrates its robustness.
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Hans, Mathieu Claude. "Optimization of digital audio for Internet transmission." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/14894.
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Muhson, Said A. "Digital data transmission over mobile radio channels." Thesis, Loughborough University, 1987. https://dspace.lboro.ac.uk/2134/10838.
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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.
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RAMIREZ, MISAEL ALBERTO RABANAL. "ON-OFF DIGITAL TRANSMISSION IN OPTICAL SYSTEMS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1989. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=9248@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOUma análise de desempenho da transmissão digital, com modulação tipo ON-OFF através de fibras óticas foi feita incluindo todos os estágios do circuito. A partir desta análise foi desenvolvido um método para o dimensionamento e o cálculo da qualidade destes sistemas óticos digitais. O método permite calcular o comprimento máximo da fibra ótica em função das características dos diversos circuitos que compõem o enlace, taxa de transmissão e objetivo de qualidade.
It was made an analysis of performance of digital transmission with modulation ON-OFF through optical fiber including all circuit phases. From this analysis it was developed a method to the dimensioning and the quality calculation of these digital optical systems. This method allows to determine the maximum length of optical fiber, since the characteristics of all enlace circuits, of date rate and the quality objective are known.
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Murithi, Kirimania (Kirimania Mwiti) 1974. "IP multicast in digital television transmission infrastructure." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/86694.
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Thesis (M.Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (leaf 88).
by Kirimania Murithi.
M.Eng.and S.B.
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Guiomar, Fernando Pedro Pereira. "Digital nonlinear equalization for optical transmission systems." Doctoral thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/15977.
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Doutoramento em Engenharia EletrotécnicaThis thesis focuses on digital equalization of nonlinear fiber impairments for coherent optical transmission systems. Building from well-known physical models of signal propagation in single-mode optical fibers, novel nonlinear equalization techniques are proposed, numerically assessed and experimentally demonstrated. The structure of the proposed algorithms is strongly driven by the optimization of the performance versus complexity tradeoff, envisioning the near-future practical application in commercial real-time transceivers. The work is initially focused on the mitigation of intra-channel nonlinear impairments relying on the concept of digital backpropagation (DBP) associated with Volterra-based filtering. After a comprehensive analysis of the third-order Volterra kernel, a set of critical simplifications are identified, culminating in the development of reduced complexity nonlinear equalization algorithms formulated both in time and frequency domains. The implementation complexity of the proposed techniques is analytically described in terms of computational effort and processing latency, by determining the number of real multiplications per processed sample and the number of serial multiplications, respectively. The equalization performance is numerically and experimentally assessed through bit error rate (BER) measurements. Finally, the problem of inter-channel nonlinear compensation is addressed within the context of 400 Gb/s (400G) superchannels for long-haul and ultra-long-haul transmission. Different superchannel configurations and nonlinear equalization strategies are experimentally assessed, demonstrating that inter-subcarrier nonlinear equalization can provide an enhanced signal reach while requiring only marginal added complexity.
A presente tese foca-se no tema da equalização digital de distorções não lineares da fibra em sistemas coerentes de transmissão ótica. Tirando partido de modelos físicos bem conhecidos para a propagação de sinal em fibras óticas mono-modo, novas técnicas de equalização não linear são propostas, testadas numericamente e validadas por demonstração experimental. A estrutura dos algoritmos propostos é fortemente condicionada pela otimização do compromisso entre complexidade e desempenho, tendo em conta a sua futura implementação prática em transcetores comerciais operando em tempo-real. O trabalho desenvolvido foca-se inicialmente na mitigação das distorções não lineares intra-canal, aplicando o conceito de propagação digital inversa realizado através de filtros de Volterra. Após uma análise sistemática do núcleo de Volterra de terceira ordem, é identificado um conjunto de simplificações críticas, culminando no desenvolvimento de algoritmos de equalização não linear de baixa complexidade, formulados no domínio do tempo e frequência. A complexidade de implementação das técnicas propostas e analiticamente descrita em termos de esforço computacional e latência de processamento, através da determinação do número de multiplicações reais por amostra e do número de multiplicações realizadas em série, respetivamente. O desempenho da equalização e avaliado recorrendo a simulação numérica e validação experimental através da medição da taxa de erros. Por fim, a questão da compensação não linear inter-canal é abordada no contexto da propagação de supercanais 400G para sistemas de transmissão metro e longa distância. Nesse âmbito são experimentalmente testadas diferentes configurações de supercanal e estratégias de equalização não linear, demonstrando assim que a implementação de equalização inter-subportadora permite estender consideravelmente o alcance, requerendo apenas um esforço computacional ligeiramente superior.
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Rizk, Ziad. "Digital data transmission over an HF channel." Thesis, Loughborough University, 1996. https://dspace.lboro.ac.uk/2134/7232.
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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.
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Chandra, Mariswamy Girish. "A new binary transmission scheme for improving the performance of digital transmission systems." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409394.
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Burger-Scheidlin, Christoph. "Variable rate transmission over noisy channels." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/3318.
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Hybrid automatic repeat request transmission (hybrid ARQ) schemes aim to provide system reliability for transmissions over noisy channels while still maintaining a reasonably high throughput efficiency by combining retransmissions of automatic repeat requests with forward error correction (FEC) coding methods. In type-II hybrid ARQ schemes, the additional parity information required by channel codes to achieve forward error correction is provided only when errors have been detected. Hence, the available bits are partitioned into segments, some of which are sent to the receiver immediately, others are held back and only transmitted upon the detection of errors. This scheme raises two questions. Firstly, how should the available bits be ordered for optimal partitioning into consecutive segments? Secondly, how large should the individual segments be? This thesis aims to provide an answer to both of these questions for the transmission of convolutional and Turbo Codes over additive white Gaussian noise (AWGN), inter-symbol interference (ISI) and Rayleigh channels. Firstly, the ordering of bits is investigated by simulating the transmission of packets split into segments with a size of 1 bit and finding the critical number of bits, i.e. the number of bits where the output of the decoder is error-free. This approach provides a maximum, practical performance limit over a range of signal-to-noise levels. With these practical performance limits, the attention is turned to the size of the individual segments, since packets of 1 bit cause an intolerable overhead and delay. An adaptive, hybrid ARQ system is investigated, in which the transmitter uses the number of bits sent to the receiver and the receiver decoding results to adjust the size of the first, initial, packet and subsequent segments to the conditions of a stationary channel.
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Thom, Gary A., and Edwin Snyder. "Digital Video Telemetry System." International Foundation for Telemetering, 1996. http://hdl.handle.net/10150/608381.
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International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, CaliforniaThe ability to acquire real-time video from flight test platforms is becoming an important requirement in many test programs. Video is often required to give the flight test engineers a view of critical events during a test such as instrumentation performance or weapons separation. Digital video systems are required because they allow encryption of the video information during transmission. This paper describes a Digital Video Telemetry System that uses improved video compression techniques which typically offer at least a 10:1 improvement in image quality over currently used techniques. This improvement is the result of inter-frame coding and motion compensation which other systems do not use. Better quality video at the same bit rate, or the same quality video at a lower bit rate is achieved. The Digital Video Telemetry System also provides for multiplexing the video information with other telemetered data prior to encryption.
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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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Haddad, Nicholas. "Transmission of digital images using data-flow architecture." Ohio : Ohio University, 1985. http://www.ohiolink.edu/etd/view.cgi?ohiou1184007755.
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Samad, Salina Abdul. "Link-transmission-line modelling of wave digital filters." Thesis, University of Nottingham, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260520.
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Al-Subbagh, M. N. "Frame alignment for digital transmission : Analysis and optimization." Thesis, University of Essex, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381258.
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Beckmann, Paul Eric. "Difficulties with NTSC compatible quadrature digital data transmission." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14490.
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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.
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Rieger, James L., and Sherri Gattis. "Draft Standard for Digital Transmission of Television Images." International Foundation for Telemetering, 1988. http://hdl.handle.net/10150/615074.
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International Telemetering Conference Proceedings / October 17-20, 1988 / Riviera Hotel, Las Vegas, NevadaThis paper describes the characteristics of the HORACE digital protocol intended for transmission of black-and-white standard television images and associated data through a digital channel and reconstruction of an NTSC standard television picture at the receiving end, using adaptive transmission to allow maximum picture quality at a selected data rate. Tradeoffs are discussed for transmission rates in the range from near DC to over 40 Mbits/second. The HORACE protocol will be a government test range standard to be issued by the Telecommunications Group [TCG] of the Range Commanders' Council as RCC Document 209.
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El, Rhammad Anas. "Efficient compression for scalable transmission of digital holograms." Electronic Thesis or Diss., Institut polytechnique de Paris, 2020. http://www.theses.fr/2020IPPAT002.
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Contrairement à la stéréoscopie, l'holographie permet une visualisation 3D la plus naturelle et confortable possible. En revanche, les hologrammes numériques contiennent une grande quantité de données avec peu de corrélations. Dans la première partie de ce travail, nous avons introduit deux méthodes de compression des hologrammes numériques. Tout d'abord, nous avons décomposé l'hologramme en faisceaux lumineux en utilisant les ondelettes de Gabor. Pour des fins de compression, nous avons compacté l'expansion obtenue en utilisant l'algorithme du guillemotleft Matching Pursuitguillemotright. Ensuite, nous avons conçu un schéma de codage spécifique aux coefficients et indices des atomes de Gabor. L'approche proposée a atteint une meilleure performance par rapport aux codeurs classiques.Deuxièmement, en exploitant la dualité entre les ondelettes de Gabor et les faisceaux lumineux émis par l'hologramme, nous avons développé un schéma de codage scalable en termes de point de vue et qualité. En effet, seuls les atomes de Gabor qui émettent la lumière dans la fenêtre de l'observateur considéré sont sélectionnés, triés et puis encodés. Le débit binaire a été considérablement réduit, sans dégrader la qualité de reconstruction par rapport à celle obtenue en encodant la totalité de l'hologramme.Dans la deuxième partie de ce travail, nous avons conçu deux architectures serveur-client pour une transmission progressive d'hologrammes en fonction de la position d'observateur à l'aide d'un codage scalable. Dans la première solution, un flux binaire scalable à grain fin est généré en ligne par le serveur, après chaque notification client concernant la position de l'utilisateur. Les résultats expérimentaux ont révélé que la méthode proposée permet une visualisation rapide en décodant les premiers atomes reçus en plus d'une augmentation progressive de la qualité.Enfin, pour réduire la latence causée par la charge de calcul au moment du codage, nous avons proposé une deuxième solution où l'intégralité de l'expansion de Gabor est encodée hors ligne par le serveur, puis décodée en ligne suivant la trajectoire de l'observateur. Pour permettre un codage scalable, nous avons regroupé les atomes de Gabor à la suite d'une décomposition par blocs du plan de l'observateur. Ensuite, les atomes de chaque bloc sont affectés à différents niveaux de qualité et codés par paquets. Les tests de simulation ont montré que l'architecture proposée permet une transmission à faible latence sans augmenter significativement le coût d'encodageContrary to conventional stereoscopy, holography provides the most natural and comfortable 3D visualization. However, digital holograms contain massive amount of data with very few correlations. In the first part of this work, we introduced two methods for digital holograms compression. First, we proposed a redundant light beams-based decomposition of holograms using the Gabor wavelets. For compression purposes, we sparsified the obtained expansion using the Matching Pursuit algorithm. Then, we designed a specific encoder framework for the coefficients and indexes of Gabor atoms. The proposed approach achieved better compression performance compared to the state of the art methods. Second, by exploiting the duality between Gabor wavelets and diffracted light beams, we developed a viewpoint-quality scalable coding scheme. Indeed, for a given observer's position, only the Gabor atoms that emit light into the viewer's window are selected, sorted and then encoded. The bit rate has been significantly reduced, without degrading the reconstruction quality obtained by encoding the whole hologram. In the second part of this work, we designed two server-client architectures for a view-dependent progressive transmission of holograms using scalable coding. In the first solution, a fine-grain scalable bitstream is generated online by the server, after each client notification about the user's position. Experimental results reveal that this method enables a rapid visualization by decoding the first received atoms in addition to a progressive increase of quality.Finally, to reduce the latency caused by the computational burden of encoding, we proposed a second solution where the whole Gabor expansion is encoded offline by the server, and then decoded online with respect to the viewer’s trajectory. To enable a scalable compression, we grouped the Gabor atoms following a block-based decomposition of the observer plane. Then, the atoms of each block are assigned to different quality levels and encoded in packets. Simulations tests show that the proposed architecture allows a low-latency transmission without significantly increasing the encoding rate
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Chongburee, Wachira. "Digital Transmission by Hermite N-Dimensional Antipodal Scheme." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/11110.
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A new N-dimensional digital modulation technique is proposed as a bandwidth efficient method for the transmission of digital data. The technique uses an antipodal scheme in which parallel binary data signs baseband orthogonal waveforms derived from Hermite polynomials. Orthogonality guarantees recoverability of the data from N simultaneously transmitted Hermite waveforms. The signed Hermite waveform is transmitted over a radio link using either amplitude or frequency modulation. The bandwidth efficiency of the amplitude Hermite method is found to be as good as filtered BPSK in practice, while the bit error rates for both modulations are identical. Hermite Keying (HK), the FM modulation version of the N-dimensional Hermite transmission, outperforms constant envelope FSK in terms of spectrum efficiency. With a simple FM detector, the bit error rate of HK is as good as that of non-coherent FSK. In a frequency selective fading channel, the simulation results suggest that specific data bits of HK are relatively secure from errors, which is beneficial in some applications. Symbol synchronization is critical to the system. An optimal synchronization method for the N-dimensional antipodal scheme in additive white Gaussian noise channel is derived. Simulation results confirm that the synchronizer can operate successfully at E/No of 3 dB.Ph. D.
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Sant'Ana, Roberto Garcia Rosa. "Investigation of new digital protection for multi-terminal power lines." Thesis, University of Manchester, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334628.
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Shahri, Javad Yazdani Kohneh. "High frequency digital power line transmission for terrestrial and marine networks." Thesis, Lancaster University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288950.
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Usta, Ö. "A power based digital algorithm for the protection of embedded generators." Thesis, University of Bath, 1992. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251234.
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Muthukkumarasamy, Vallipuram. "Data assisted equalisation for high speed digital transmission systems." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334181.
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Ghassemi, Foroozan. "Adaptive digital distance protection for series compensated transmission lines." Thesis, City University London, 1989. http://openaccess.city.ac.uk/8235/.
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Series capacitors offer considerable technical and economical advantages in long distance a.c. transmission. In particular, their excellent reliability and minimal maintenance requirements make series compensation the most cost effective method of enhancing the power transfer capability of an existing or proposed interconnection. E.H.V. lines employing series capacitors however, pose difficult problems for the line protection relays, not encountered with plain feeders. One important cause of these problems is the resonance between the series capacitor and the line series inductance, which in turn imposes a sub-synchronous oscillation on the system signals. Also, the rapid changes in the circuit parameters, resulting from the operation of the capacitor protection equipment, namely the spark gaps, introduce some difficulties for the line protection schemes, especially an impedance measuring relay. These spark gaps are installed in parallel with the series capacitors to prevent the development of very high voltages across the capacitor which could cause excessive damage to the equipment. The work presented herein describes a new digital distance relay suitable for series compensated line applications. The errors in the impedance measurement for a phase to earth fault when the spark gaps do not flash over, are discussed and new methods are proposed to compensate for these errors. The new concept of a complex residual compensation factor, as opposed to a real one, is also discussed. A new adaptive filtering is incorporated in the relay in order to minimise the detrimental effect of the subsynchronous oscillation on the relay decision logic. Finally, the relay is thoroughly tested for many different system configurations, to fully evaluate the relay response.
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Butler, Richard. "Aspects of burst errors in digital telecommunications transmission systems." Thesis, Robert Gordon University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386407.
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Harbinja, Edina. "Legal aspects of transmission of digital assets on death." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=28644.
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This thesis explores the key issues surrounding the transmission of digital assets on death. To answer this primary research questions, the author first looks at the legal nature of digital assets, which are defined as any asset of personal or economic value online (capable of post-mortem transmission). She then analyses in depth the three most typical and widely used types of assets: virtual worlds, emails and social networks. In trying to reach decisions on the legal nature of digital assets, the thesis first looks for help to the institution of property. If an asset can be considered the property of the deceased user, then in most countries it forms part of an estate and transmits on death. The same goes for intellectual property (primarily copyright herein). If an asset cannot and should not be considered property, or protected by copyright, then arguably it cannot transmit on death. The thesis finds that email contents, virtual world items and social network contents are not and should not be considered as property. Some of this content can, however, be protected by copyright and thus is transmissible on death. If significant user interests and expectations exist in the transmission of digital assets on death, therefore, legislative action will be required in the areas of copyright and succession laws. The research demonstrates that some of the content, primarily information and personal data, is neither property nor protected by copyright. For this content, the analysis discusses some alternative legal institutions (breach of confidence, data protection) and argues that their protection can be extended to include the deceased users. The thesis thus introduces a novel phenomenon of post-mortem privacy, the protection of privacy interests of the deceased. It argues that this phenomenon merits a policy and legal account and submits that this concept should foster the user’s autonomy and control, preventing the default transmission of digital assets on death. The thesis further looks at the allocation of ownership of assets through service providers’ contracts, finding a contradictory approach of service providers regarding ownership and transmission of digital assets. These contracts usually curtail the users’ autonomy and control over their assets in life and post-mortem. There have been some recent technological developments led by Google and Facebook, which enable an in-service transmission on the death of some of the content associated with these accounts. These solutions are not free from problems, and the thesis evaluates them and proposes some improvements. User’s autonomy is the main underpinning value of the thesis and the basis for some tentative solutions suggested in the thesis.
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Oliveira, Inês do Vale Marques. "Digital chromatic dispersion equalization in optical coherent transmission systems." Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/21735.
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Mestrado em Engenharia Eletrónica e TelecomunicaçõesA crescente procura de largura de banda tem obrigado a área de comunicações óticas a explorar diferentes soluções, de forma a evitar a ”crise de capacidade” [1]. O investigadores têm trabalhado no sentido de atingir o equilíbrio entre os vários compromissos, repensando a forma como o sinal ótico é enviado e recebido, para que a perda de informação seja mínima ao longo do canal de propagação. No inıcio desta década, começaram a ser adotados formatos de modulação avançada, os quais apresentam elevada eficiência espetral, bem como deteção coerente, que permite extrair a informação da amplitude e da fase do campo ótico. Estas técnicas são complementadas pelo pós-processamento digital de sinal, que é atualmente muito importante na mitigação das distorções do sinal e imperfeiçoes do recetor. As distorções do sinal podem ser causadas, por exemplo, pela dispersão cromática na fibra. Esta dissertação engloba o estudo e simulação de um sistema de transmissão coerente PM-QPSK, bloco-a-bloco, fazendo uma abordagem detalhada dos conceitos supramencionados. O sistema foi então simulado na presença de dispersão cromática e de ruído, alternada e simultaneamente. Os resultados mostram que o sinal recebido apresenta uma distribuição quase Gaussiana em todos os casos. Com vista a recuperar o sinal transmitido, e no caso em que só se considerou o efeito da dispersão cromática, aplicou-se um filtro linear de resposta impulsional inversa à da fibra, conseguindo assim uma equalização digital perfeita do sinal recebido. Também foi implementado um filtro adaptado no receptor para minimizar o efeito do ruído, obtendo não uma equalização perfeita, mas ótima.
The crescent demand on high bandwidth has been compelling the optical communications area to explore di erent solutions, in order to avoid the \capacity crunch" of the optical bres [1]. Researchers have been working towards reaching the best tradeo s balance, rethinking the way as the optical signal is sent and received, so the loss of information is minimum throughout the propagation channel. Advanced modulation formats became adopted in the beginning of this decade, presenting high spectral e ciency, as well as coherent detection, which allows extracting information from the amplitude and phase of the optical eld. These techniques are complemented by post-digital signal processing, which is nowadays very important at mitigating signal distortions and receiver imperfections. Those impairments result, for instance, of the chromatic dispersion at the bre. This dissertation covers the study and simulation of a PM-QPSK transmission system, block-by-block, approaching in detail the concepts mentioned above. The system was then simulated with chromatic dispersion and with noise, alternately and simultaneously. The results show that the received signal presents an almost Gaussian distribution in every case. In order to retrieve the transmitted signal, and in the case that only chromatic dispersion's e ect was considered, a linear lter was applied with an inverse impulse response of the bre, achieving such a perfect digital equalization of the received signal. A matched lter was also implemented in the receptor to minimize the noise e ect, obtaining not a perfect equalization, but an optimal one.
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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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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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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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Fu, Deng Yuan. "ADAPTIVE DIGITAL IMAGE DATA COMPRESSION BY RECURSIVE IDPCM." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275350.
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Chee, Thean S. (Thean Sang) Carleton University Dissertation Engineering Electrical. "Oversampled analog-to-digital converter and subscriber line channel modelling for digital subscriber loop transmission." Ottawa, 1990.
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Carvalho, Silvio Renato Messias de 1960. "Contribuições para melhoria da confiabilidade de redes de frequência única em sistemas de transmissão de TV digital." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/261224.
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Orientador: Yuzo IanoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: Este trabalho apresenta uma nova proposta para o conceito de redes de frequência única, SFN. Redes de radiodifusão em SFN são assim chamadas por utilizarem um único canal de transmissão ou uma única frequência. Nesta proposta os transmissores de uma rede SFN são conectados formando uma rede real que por sua vez se interliga a pontos receptores chamados de pontos monitores estrategicamente localizados dentro da área de cobertura. Uma rede de radiodifusão que possa se adaptar dinamicamente às variações das condições do canal é útil porque aumenta a confiabilidade da rede. A modificação proposta apresenta vantagens para as emissoras de televisão que possuam redes de retransmissão destinadas a ampliar sua cobertura em uma área regional com várias cidades obtendo um ambiente de rede muito mais controlado e seguro. O conceito também pode ser aplicado a gap-fillers e repetidores de mesmo canal on channel. O trabalho apresenta simulações de cobertura para mostrar as variações do canal e a resposta da rede
Abstract: This paper presents a new approach for the concept of single frequency networks, SFN. SFN broadcasting networks are so named because they use a single transmission channel or a single frequency. In this proposal the transmitters in a SFN network are connected together to form a real network that in turn connects to receptor sites called 'monitor point' strategically located within the coverage area. A broadcasting network that can dynamically adapt to changing channel conditions is useful because it increases network reliability. The proposed modification has advantages for television stations that have relay stations aiming to expand its coverage in a regional area with a network more controlled and secure. The concept can also be applied to gap- fillers and repeaters on channel. This work presents simulations of coverage to show variations in channel and network response
Doutorado
Telecomunicações e Telemática
Doutor em Engenharia Elétrica
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Yong, Yoke Chuang. "Receive channel architecture and transmission system for digital array radar." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Dec%5FYong.pdf.
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Thesis (M.S. in Combat Systems Technology)--Naval Postgraduate School, December 2005.Thesis Advisor(s): David C. Jenn, Donald L. Walters. Includes bibliographical references (p.75-76). Also available online.
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Liang, Feng. "Performance enhancement of digital relays for transmission line distance protection /." Internet access available to MUN users only, 2003. http://collections.mun.ca/u?/theses,153681.
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Föllscher, Heiko. "Transmission of media content on IP-based digital broadcast platforms /." Aachen : Shaker, 2007. http://www.gbv.de/dms/bs/toc/543512584.pdf.
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McGleenon, Patrick. "Modelling the management behaviour of synchronous digital hierarchy transmission networks." Thesis, Queen's University Belfast, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361221.
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Zhu, S. "Digital communications over dispersive channels using pre-transmission pulse shaping." Thesis, University of Essex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374731.
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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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Dogheche, El Hadj. "Transmission optique d'un signal analogique hyperfréquence et digital bas débit." Lille 1, 1993. http://www.theses.fr/1993LIL10056.
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Le centre national d'études spatiales de Toulouse a envisagé, dans ses projets spot 2000 et radar 2000, la possibilité de remplacer les liaisons classiques (câble coaxial) reliant l'antenne active et le cur du satellite, par des liaisons à fibre optique. Cette étude a consisté à étudier le transport microonde d'une liaison optohyperfréquence. Celle-ci est réalisée à l'aide de composants optoélectroniques commerciaux fibres, et utilise la modulation directe de l'émetteur. Nous démontrons la possibilité d'améliorer le bilan de transfert de la liaison par l'adaptation d'impédance passive réactive des composants d'extremité. Une amélioration de l'ordre de 7 db a été obtenue dans une bande de 400 mhz autour de 2,2 ghz (20%). La caractérisation microonde de la transmission optique avec adaptation, menée à 2,2 ghz, a permis de relever des pertes d'insertion de 9 db, ainsi qu'une dynamique en sortie de 65 db. Mhz. L'étude du transport d'un signal microonde module a ensuite été entreprise. Après avoir comparé les divers types de modulation, nous nous sommes plus particulièrement attachés à analyser le comportement de la liaison, pour un signal hyperfréquence modulé en phase par un signal digital (modulation bpsk). Les principaux paramètres expérimentaux caractéristiques (plots de phase, réponse temporelle et spectrale,. . . ) n'ont montré qu'aucune dégradation significative n'était apportée par le transport optique. Le prolongement de ce travail a consisté à augmenter la fréquence du signal microonde dans la liaison optique. Une première démonstration a ainsi été réalisée à 6 ghz sur une liaison utilisant des composants de laboratoire fabriqués à thomson-lcr. Nous avons également envisagé l'utilisation des non-linéarites du laser pour la régénération de signaux microondes harmoniques.
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Jalal, Rakib S. "Transmission of image data over digital networks involving mobile terminals." Thesis, Aston University, 1990. http://publications.aston.ac.uk/8084/.
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There is a growing demand for data transmission over digital networks involving mobile terminals. An important class of data required for transmission over mobile terminals is image information such as street maps, floor plans and identikit images. This sort of transmission is of particular interest to the service industries such as the Police force, Fire brigade, medical services and other services. These services cannot be applied directly to mobile terminals because of the limited capacity of the mobile channels and the transmission errors caused by the multipath (Rayleigh) fading. In this research, transmission of line diagram images such as floor plans and street maps, over digital networks involving mobile terminals at transmission rates of 2400 bits/s and 4800 bits/s have been studied. A low bit-rate source encoding technique using geometric codes is found to be suitable to represent line diagram images. In geometric encoding, the amount of data required to represent or store the line diagram images is proportional to the image detail. Thus a simple line diagram image would require a small amount of data. To study the effect of transmission errors due to mobile channels on the transmitted images, error sources (error files), which represent mobile channels under different conditions, have been produced using channel modelling techniques. Satisfactory models of the mobile channel have been obtained when compared to the field test measurements. Subjective performance tests have been carried out to evaluate the quality and usefulness of the received line diagram images under various mobile channel conditions. The effect of mobile transmission errors on the quality of the received images has been determined. To improve the quality of the received images under various mobile channel conditions, forward error correcting codes (FEC) with interleaving and automatic repeat request (ARQ) schemes have been proposed. The performance of the error control codes have been evaluated under various mobile channel conditions. It has been shown that a FEC code with interleaving can be used effectively to improve the quality of the received images under normal and severe mobile channel conditions. Under normal channel conditions, similar results have been obtained when using ARQ schemes. However, under severe mobile channel conditions, the FEC code with interleaving shows better performance.
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Silva, Alexandre Fieno da. "No-reference video quality assessment model based on artifact metrics for digital transmission applications." reponame:Repositório Institucional da UnB, 2017. http://repositorio.unb.br/handle/10482/24733.
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Tese (doutorado)—Universidade de Brasília, Instituto de Ciências Exatas, Departamento de Ciência da Computação, 2017.Submitted by Raquel Almeida (raquel.df13@gmail.com) on 2017-06-22T19:03:58Z No. of bitstreams: 1 2017_AlexandreFienodaSilva.pdf: 5179649 bytes, checksum: de1d53930e22f809bd34322d5c5270d0 (MD5)
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Um dos principais fatores para a redução da qualidade do conteúdo visual, em sistemas de imagem digital, são a presença de degradações introduzidas durante as etapas de processamento de sinais. Contudo, medir a qualidade de um vídeo implica em comparar direta ou indiretamente um vídeo de teste com o seu vídeo de referência. Na maioria das aplicações, os seres humanos são o meio mais confiável de estimar a qualidade de um vídeo. Embora mais confiáveis, estes métodos consomem tempo e são difíceis de incorporar em um serviço de controle de qualidade automatizado. Como alternativa, as métricas objectivas, ou seja, algoritmos, são geralmente usadas para estimar a qualidade de um vídeo automaticamente. Para desenvolver uma métrica objetiva é importante entender como as características perceptuais de um conjunto de artefatos estão relacionadas com suas forças físicas e com o incômodo percebido. Então, nós estudamos as características de diferentes tipos de artefatos comumente encontrados em vídeos comprimidos (ou seja, blocado, borrado e perda-de-pacotes) por meio de experimentos psicofísicos para medir independentemente a força e o incômodo desses artefatos, quando sozinhos ou combinados no vídeo. Nós analisamos os dados obtidos desses experimentos e propomos vários modelos de qualidade baseados nas combinações das forças perceptuais de artefatos individuais e suas interações. Inspirados pelos resultados experimentos, nós propomos uma métrica sem-referência baseada em características extraídas dos vídeos (por exemplo, informações DCT, a média da diferença absoluta entre blocos de uma imagem, variação da intensidade entre pixels vizinhos e atenção visual). Um modelo de regressão não-linear baseado em vetores de suporte (Support Vector Regression) é usado para combinar todas as características e estimar a qualidade do vídeo. Nossa métrica teve um desempenho muito melhor que as métricas de artefatos testadas e para algumas métricas com-referência (full-reference).
The main causes for the reducing of visual quality in digital imaging systems are the unwanted presence of degradations introduced during processing and transmission steps. However, measuring the quality of a video implies in a direct or indirect comparison between test video and reference video. In most applications, psycho-physical experiments with human subjects are the most reliable means of determining the quality of a video. Although more reliable, these methods are time consuming and difficult to incorporate into an automated quality control service. As an alternative, objective metrics, i.e. algorithms, are generally used to estimate video quality quality automatically. To develop an objective metric, it is important understand how the perceptual characteristics of a set of artifacts are related to their physical strengths and to the perceived annoyance. Then, to study the characteristics of different types of artifacts commonly found in compressed videos (i.e. blockiness, blurriness, and packet-loss) we performed six psychophysical experiments to independently measure the strength and overall annoyance of these artifact signals when presented alone or in combination. We analyzed the data from these experiments and proposed several models for the overall annoyance based on combinations of the perceptual strengths of the individual artifact signals and their interactions. Inspired by experimental results, we proposed a no-reference video quality metric based in several features extracted from the videos (e.g. DCT information, cross-correlation of sub-sampled images, average absolute differences between block image pixels, intensity variation between neighbouring pixels, and visual attention). A non-linear regression model using a support vector (SVR) technique is used to combine all features to obtain an overall quality estimate. Our metric performed better than the tested artifact metrics and for some full-reference metrics.
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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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Lundbäck, Jonas. "On signal processing and electromagnetic modelling : applications in antennas and transmission lines /." Karlskrona : Department of Signal Processing, School of Engineering, Blekinge Institute of Technology, 2007. http://www.bth.se/fou/Forskinfo.nsf/allfirst2/62a51cd9a6f3d716c12572c1003f0063?OpenDocument.
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