Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2008. / M.Phil. in Electronic Technology. Includes bibliographical references (p. 57-58).

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

M.Ing. / There is a growing demand for HD video content. That demand requires significant bandwidth, even with sophisticated compression schemes. As the demand increases in popularity, the bandwidth requirement will become burdensome on networks. In an effort to satisfy the demand for HD, improved compression schemes need to be investigated together with increasing efficiency of transmission. The purpose of this literature study is to investigate existing video compression schemes and techniques used in software implementations. Then to build on existing work within the mature field of video compression, in order to propose a new scheme which would then be tested for viability. Two algorithms were proposed as a result of the literature study. The first algorithm is an improved way to add colour to luminance images of similar scene content. The second algorithm is an encoding scheme that is adaptive to the video content. The proposed encoding scheme adaptively selects to encode the next several frames using well established techniques or to use a technique proposed in this work. At the time of preparing this document, and from the available literature this second proposed algorithm is new. An interesting compression tool has been developed during this study. This tool can be used to obtain a visual expectation of the achievable compression before applying the compression. The tool is a quadrant plot of the difference in image entropy between successive frames and an estimation of the mean percentage motion content between these frames. Over the duration of a scene, the spread of results reveals the extent of the potential compression gain.

Chan, Pui Wai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 81-83). / Abstracts in English and Chinese. / Abstract --- p.ii / Acknowledgement --- p.iv / Contents --- p.v / Chapter I. --- Introduction --- p.1 / Chapter II. --- Details of UWB System --- p.3 / Background --- p.3 / Technical Information --- p.3 / Applications --- p.11 / Chapter III. --- Theoretical Explanation on Orthogonal Frequency Division Multiplexing (OFDM) Technology --- p.13 / Chapter IV. --- Design of OFDM De-modulator --- p.21 / Multipath Delay Commutator (MDC) --- p.24 / Single-path Delay Feedback (SDF) --- p.25 / Multipath Delay Feedback (MDF) --- p.27 / Chapter V. --- Designs of Multipliers in UWB FFT module --- p.33 / Twiddle Factor Multiplication - Group 1 --- p.33 / Twiddle Factor Multiplication - Group 2 --- p.34 / Twiddle Factor Multiplication - Group 3 --- p.45 / Baugh-Wooley Algorithm --- p.46 / Modified-Booth Algorithm --- p.47 / Hardware Architecture of Multipliers --- p.54 / Partial Product Accumulator - Array Architecture --- p.55 / Partial Product Accumulator - Tree Architecture --- p.59 / Fixed-width Multiplier --- p.61 / Chapter VI. --- Comparison Methodology --- p.65 / Standard Cell Design Flow --- p.66 / FPGA Design Flow --- p.69 / Chapter VII. --- Simulation Results and Discussion --- p.71 / Simulation results of FFT module using Standard Cell Methodology --- p.71 / Simulation results of FFT module using FPGA Methodology --- p.74 / Discussion on Simulation results of FFT module using ASIC and FPGA Methodology --- p.77 / Area / Slice Usage --- p.77 / Power Consumption --- p.77 / APS/SPS --- p.78 / General Guidelines For Designing FFT Module For Other Systems --- p.78 / Chapter VIII. --- Conclusion --- p.80 / Chapter IX. --- Future Works --- p.80 / Reference --- p.81

UWB communication is an attractive technology that has the potential to provide low-power, low-complexity, and high-speed communications in short range links. One of the main challenges of the UWB communications is the highly frequency-selective channel, which induces hundreds of overlapped copies of the transmitted pulse with different delays and amplitudes. To collect the energy of these multipath components, coherent Rake receivers are proposed, but suffer from high implementation and computational costs on channel estimation. To avoid the stringent channel estimation, several noncoherent receivers, including energy detector (ED) and transmitted reference (TR), are proposed at the cost of degraded performance. In addition, when taking into account practical issues of UWB communications, e.g., non-Gaussian impulsive noise, non-ideal antennas, and limited, significant performance degradation may be introduced by noncoherent receivers. In this dissertation, we will present low-complexity, high-performance, noncoherent receiver designs for UWB communications that i) avoid the stringent channel estimation; ii) lower the computational complexity of the existing receivers with the aid of advanced digital signal processing techniques; and iii) improve the error performance of the noncoherent receivers by accommodating practical imperfections. First, we propose three multi-symbol detectors (MSDs) for multi-symbol different detection (MSDD), which has recently caught attention in UWB communications because of its high performance without requiring explicit channel estimation. To alleviate the non-deterministic polynomial hardness (NP-hard) of MSDD, we analyze the statistical model of MSDD and propose an iterative MSD and two MSDs based on relaxation technique with near-optimal performance and low complexity. Moreover, the error performance of MSDs is further enhanced by exploiting joint soft-input soft-output MSDD and forward error correction codes. Next, we consider the non-Gaussian noise in the presence of multi-access interference, which is impulsive when the number of active users is small. To mitigate the impulsive noise effect, in this dissertation, we propose new differential UWB receivers based on the generalized Gaussian distribution and Laplace distribution and achieve better error performance. Another main issue of UWB communications is the limited radio coverage. To extend the coverage and improve the performance of UWB systems, we focus on a novel differentially encoded decode-and-forward (DF) non-cooperative relaying scheme. Putting emphasis on the general case of multi-hop relaying, we illustrate a novel algorithm for the joint power allocation and path selection (JPAPS), minimizing an approximate of the overall bit error rate (BER). A simplified scheme is also presented, which reduces the complexity to O(N²) and achieves a negligible performance loss. Finally, we concentrate on code-multiplexing (CM) systems, which have recently drawn attention mainly because they enable noncoherent detection without requiring either a delay component, as in TR, or an analog carrier, as in frequency-shifted reference. In this dissertation, we propose a generalized code-multiplexing (GCM) system based on the formulation of a constrained mixed-integer optimization problem. The GCM extends the concept of existing CM while retaining their simple receiver structure, even offering better BER performance and a higher data rate in the sense that more data symbols can be embedded in each transmitted block. Moreover, the impacts of non-ideal antennas on the GCM systems are investigated given some practical antenna measurement data and IEEE 802.15.4a channel environments.

Timing offsets result from the use of real clocks that are non-ideal in sampling intervals. These offsets also known as timing jitter were shown to degrade the performance of the two forms of UWB systems impulse radio and orthogonal frequency division multiplexing (OFDM)-based UWB. It was shown that for impulse radio, timing jitter distorts the correlation property of the transmitted signal and the resulting performance loss is proportional to the root-mean-square (RMS) value of the timing jitter. For the OFDM-based UWB, timing jitter introduced inter-channel interference (ICI) and the performance loss was dependent on the product of the bandwidth and the RMS of the timing jitter. A number of techniques were proposed for mitigating the performance degradation in each form of UWB. Specifically, for impulse radio, the methods of pulse shaping and sample averaging were provided, whereas for OFDM-based UWB, oversampling and adaptive modulation were given. Through analysis and simulation, it was shown that substantial gain in signal power-to-noise ratio can be achieved using these jitter-reduction methods.

Les avancées technologiques de ces dernières années, combinées au succès avéré et toujours croissant des communications sans fil, ont tout naturellement donné naissance à un nouveau type de réseaux sans fil, communément appelés Body Area networks. A terme, ces réseaux corporels sans fil doivent permettre à un ensemble de senseurs bio-médicaux répartis sur le corps humain de communiquer, soit pour échanger des informations en vue d'un traitement en temps réel du patient, soit pour enregistrer des données physiologiques en vue d'une analyse ultérieure.<p><p>L’objectif de cette Thèse vise la réduction de la consommation énergétique au niveau des senseurs de sorte à leur garantir une autonomie de quelques mois, voire de quelques années. En réponse à cette contrainte énergétique, une association innovante de deux technologies émergentes est proposée, à savoir une combinaison des transmissions à ultra-large bande aux systèmes à multiples antennes. Une nouvelle architecture pour les réseaux corporels sans fil est donc envisagée pour laquelle les performances doivent être évaluées. Notre principale contribution à cet objectif consiste en la proposition d'une modélisation spatio-temporelle complète du canal de transmission dans le cadre de senseurs répartis autour du corps. Cette modélisation fait appel à la définition de nouveaux modèles, l'élaboration d'outils spécifiques d'extraction de paramètres et une compréhension fine des mécanismes de propagation liés à la proximité du corps humain. Ce manuscrit présente les résultats majeurs de nos recherches en cette matière.<p> / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

Actuellement, la majorité des équipements électroniques prenant place dans nos véhicules s'interconnectent encore par des liens câblés. Or, l'établissement d'un réseau sans fil permet de remplacer ces liens existants. Afin de permettre cette connectivité et pour répondre aux exigences futures, une solution qui accepte suffisamment de débit doit être développée. Parmi les solutions actuelles possibles, l'Ultra-Large Bande est le candidat idéal. De manière générale, cette Thèse se consacre à l'étude de la propagation à l'intérieur d'une voiture. Afin d'évaluer les performances de ce type de système à l'intérieur d'un véhicule, un modèle de canal pouvant reproduire avec fidélité la propagation intra-véhiculaire est nécessaire. De par la similarité entre les environnements, le modèle de canal proposé est basé sur la théorie des chambres réverbérantes. Compte tenu des faibles dimensions de l'environnement et de la proximité des antennes par rapport aux passagers, l'idée est de réduire l'énergie absorbée par ces derniers tout en maximisant celle-ci à la position d'un récepteur visé. Parmi les solutions possibles, le retournement temporel apparait comme une technique idéale pour répondre à ces objectifs. Cette technique permet en effet de focaliser temporellement et spatialement le signal électromagnétique au niveau du récepteur. Dans cette Thèse, une évaluation des performances du RT à l'intérieure d'une voiture est proposée. Cette étude nous a amenés à porter notre attention sur les propriétés spatiales de l'énergie totale portée par un signal utilisant le retournement temporel et, de ce fait, nous proposons un nouveau formalisme de la distribution spatiale de cette énergie. / Current vehicles still use wired links to interconnect the embedded electronic equipment. However, advances in wireless technologies permit to replace these links with wireless personal area networks. To enable this connectivity and to meet the future requirements, a solution that provides sufficient data rate must be developed. One technological candidate that can be used to meet the data rate requirements is Ultra-Wide Band. This thesis investigates the ultra-wideband propagation environment in intra-vehicular environments. In order to evaluate the performances of UWB inside a vehicle, channel models that accurately reproduce the intra-vehicular propagation characteristics are required. Because of obvious similarities, the proposed model is based on reverberation chamber theory. Given the small size of the environment and the proximity of the antennas to the passengers, one goal of intra-vehicular communications is to reduce the energy absorbed by the passengers while maximizing the energy at the position of the intended receiver. Among the possible solutions, Time Reversal appears to be the ideal technique to meet this objective. Time Reversal permits to spatially and temporally focus the electromagnetic signal at the receiver. In this thesis, a performance evaluation of Time Reversal inside a car is proposed. Moreover, a model of the spatial properties of the total energy of a signal using Time Reversal is proposed. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished