Visible light communication (VLC) systems take advantage of ubiquitous light-emitting diodes (LED) and leverage existing illumination infrastructure to provide broadband optical communication links. Multiple-input multiple-output (MIMO) VLC systems are among the well studied topics in VLC research. However, most traditional MIMO VLC systems require accurate alignment and have to adjust to different magnifications at various link distances. Consequently, the alignment and calibration modules increase the complexity of the receiver structures. A pixelated MIMO VLC system is introduced in this thesis, which transmits a series of time-varying coded images that can be received and decoded by commercial digital cameras. Using a convex lens placed in front of the transmitter at its focal length, the system exploits the Bokeh effect to obtain fixed-scale images at all link distances. Compared with traditional pixelated MIMO VLC systems, which send information directly in space, this spatial-angular mapping system sends information in different angles instead. In contrast to the complex receiver structures in traditional setups, the proposed system can capture fixed-scale images with a simple receiver requiring no re-focusing as the camera moves. The channel model of the system is measured and modeled and a rateless code is applied to track the truncation of receive images for various link ranges and angular offsets. A proof-of-concept optical communication system is implemented with an LCD display and a high speed CMOS camera. Performance of the system is measured and analysed. The experimental system can achieve a throughput of approximately 10 bit per frame over 90 cm. This fixed-scale pixelated MIMO wireless optical communication system provides a less expensive option for short-range indoor broadcasting optical links and inter-vehicle communications due to its mobility, stability and simpler receiver structure compared to traditional designs in different working conditions. / Thesis / Master of Applied Science (MASc)

Multiple-input multiple-output (MIMO) systems have recently emerged as one of the most significant wireless techniques, as they can greatly improve the channel capacity and link reliability of wireless communications. These benefits have encouraged extensive research on a virtual MIMO system where the transmitter has multiple antennas and each of the receivers has a single antenna. Single-antenna receivers can work together to form a virtual antenna array and reap some performance benefits of MIMO systems. The idea of receiver-side local cooperation is attractive for wireless networks since a wireless receiver may not have multiple antennas due to size and cost limitations. In this thesis we investigate a virtual-MIMO wireless system using the receiver-side cooperation with the compress-and-forward (CF) protocol. Firstly, to perform CF at the relay, we propose to use standard source coding techniques, based on the analysis of its expected rate bound and the tightness of the bound. We state upper bounds on the system error probabilities over block fading channels. With sufficient source coding rates, the cooperation of the receivers enables the virtual-MIMO system to achieve almost ideal MIMO performance. A comparison of ideal and non-ideal conference links within the receiver group is also investigated. Considering the short-range communication and using a channel-aware adaptive CF scheme, the impact of the non-ideal cooperation link is too slight to impair the system performance significantly. It is also evident that the practicality of CF cooperation will be greatly enhanced if a efficient source coding technique can be used at the relay. It is even more desirable that CF cooperation should not be unduly sensitive to carrier frequency offsets (CFOs). Thus this thesis then presents a practical study of these two issues. Codebook designs of the Voronoi VQ and the tree-structure vector quantization (TSVQ) to enable CF cooperation at the relay are firstly described. A comparison in terms of the codebook design complexity and encoding complexity is presented. It is shown that the TSVQ is much simpler to design and operate, and can achieve a favourable performance-complexity tradeoff. We then demonstrate that CFO can lead to significant performance degradation for the virtual MIMO system. To overcome it, it is proposed to maintain clock synchronization and jointly estimate the CFO between the relay and the destination. This approach is shown to provide a significant performance improvement. Finally, we extend the study to the minimum mean square error (MMSE) detection, as it has a lower complexity compared to maximum likelihood (ML) detection. A closed-form upper bound for the system error probability is derived, based on which we prove that the smallest singular value of the cooperative channel matrix determines the system error performance. Accordingly, an adaptive modulation and cooperation scheme is proposed, which uses the smallest singular value as the threshold strategy. Depending on the instantaneous channel conditions, the system could therefore adapt to choose a suitable modulation type for transmission and an appropriate quantization rate to perform CF cooperation. The adaptive modulation and cooperation scheme not only enables the system to achieve comparable performance to the case with fixed quantization rates, but also eliminates unnecessary complexity for quantization operations and conference link communication.

This thesis first addresses an important topic concerning space structure control systems, namely, attitude stabilization and control, which is followed by a study on subsystem interactions of general Multi Input Multi Output (MIMO) systems for better performance and actuator fault tolerance. A novel and simple output feedback stabilization approach is proposed for a space structure system characterized with kinematics and dynamics. The approach globally, asymptotically stabilizes the plant and the closed-loop stability is proved using Lyapunov analysis. The simplicity and robustness of the designed controller are demonstrated by investigating the closed-loop response after reducing the degree of freedom in control structure. The stability of the closed-loop system is further analyzed and the performance is compared with two other robust control approaches. The study carries on to another space plant, a Large Space Telescope (LST). Its dynamic model which is fitted with reaction wheels initially developed by NASA is analyzed and the fully coupled dynamics are derived by taking into account the nonlinear coupling phenomena and other terms neglected in their original (NASA) form. The dynamics are combined with Quaternion based kinematics to form an intricate yet realistic LST attitude model. The attitude of the nonlinear LST model is stabilized using a state feedback controller and the LST model is shown to track a time varying attitude reference. Structure configuration is an imperative task in the design of MIMO control systems. In order to make use of interactions between multiple channels so that the system can deal with vulnerability due to actuator degradation, a novel interaction measure is proposed. It is defined as Relative Dependency Index (RDI) and is based on H∞ norms. Such a measurement is effective in understanding the influence of the jth input on the ith output of a system. RDI based guidelines are outlined for configuring a system towards coupling/decoupling. RDI is further extended to the Input Impact Index (i.i.i.) which helps in determining how much an actuator degradation would affect the output of a system. The validity of RDI and i.i.i. is illustrated by simulation results and tested on the linearized spacecraft attitude model presented in the former part of the thesis.

Multiple-input Multiple-output (MIMO) wireless communication systems allow increased spectral efficiency and therefore promise significant improvement in performance. However, because of the rapid variation in channel state information (CSI) in networks with mobile nodes or scatterers, it is difficult both to maintain high communication performance and to create channel models that effectively represent the time-varying behavior of the channels. The spatial covariance of the MIMO channel describes the average power gain on each transmit-receive antenna pair as well as the correlation between the complex link gains and thus provides critical information for understanding the performance of the system and for creating models to accurately describe the interaction of the electromagnetic fields with the antennas. Furthermore, in many cases the MIMO signaling scheme uses knowledge of this spatial covariance. This thesis proposes a closed-form analytical model that allows estimation of the full MIMO channel covariance based on knowledge of the power angular spectrum (PAS) of the channel and the antenna radiation patterns. Comparison of covariance matrices computed using this model with those estimated from observed channel samples reveals the appropriate window over which the covariance should be estimated for non-WSS time-varying channels. Two approaches are developed to compare the covariance matrices in order to determine the appropriate window, both based on a metric, correlation matrix distance (CMD). Simulations based on both a two-ring propagation model and raytracing data in a three dimensional urban environment are included. The results reveal that with the optimal window size, the CMD of the estimated covariance is close to that of the analytical covariance. An average window size normalized by the scatterer circle radius is determined for practical estimation of covariance based on knowledge of the average distance to the scatterers. The impact of the number of scatterers on the optimal window size is analyzed as well. The results based on ray-tracing data show that the CMD of the estimated covariance using a 16 – 17λ window match the CMD of the analytical covariance.

The focus of this thesis is peak-to-average power ratio (PAPR) reduction in cooperative wireless networks which exploit orthogonal frequency division multiplexing in transmission. To reduce the PAPR clipping is employed at the source node. The first contribution focuses upon an amplify-and-forward (AF) type network with four relay nodes which exploits distributed closed loop extended orthogonal space frequency block coding to improve end-to-end performance. Oversampling and filtering are used at the source node to reduce out-of-band interference and the iterative amplitude reconstruction decoding technique is used at the destination node to mitigate in-band distortion which is introduced by the clipping process. In addition, by exploiting quantized group feedback and phase rotation at two of the relay nodes, the system achieves full cooperative diversity in addition to array gain. The second contribution area is outage probability analysis in the context of multi-relay selection in a cooperative AF network with frequency selective fading channels. The gains of time domain multi-path fading channels with L paths are modeled with an Erlang distribution. General closed form expressions for the lower and upper bounds of outage probability are derived for arbitrary channel length L as a function of end-to-end signal to noise ratio. This analysis is then extended for the case when single relay selection from an arbitrary number of relay nodes M is performed. The spatial and temporal cooperative diversity gain is then analysed. In addition, exact form of outage probability for multi-path channel length L = 2 and selecting the best single relay from an arbitrary number of relay nodes M is obtained. Moreover, selecting a pair of relays when L = 2 or 3 is additionally analysed. Finally, the third contribution context is outage probability analysis of a cooperative AF network with single and two relay pair selection from M available relay nodes together with clipping at the source node, which is explicitly modelled. MATLAB and Maple software based simulations are employed throughout the thesis to support the analytical results and assess the performance of algorithms and methods.

In rapid wireless communication technology development environment, antennas, the interface among many wireless communications, are an indispensable component for wireless systems. Miniaturization and functionality stability (high tolerance to environmental variations) of the antenna are fast becoming the design trends in research and development of wireless communication systems. They are also the main objectives of this thesis. In the first part of this thesis, we designed two highly stable antennas, which can be used in notebook computers or tablet PCs. The antenna has self-balanced characteristics, where the environmental interference is minimized, in its performance/functionality and patterns. The first antenna design, which can be easily integrated into an RF front-end board, employed capacitive coupling, differential feed printed loop configurations. Comparing to the existing differentially fed antenna design, our designs are much more miniaturized: the antenna size was 13 mm ¡Ñ 27 mm, the ground size was 4.5 mm ¡Ñ 4.5 mm. Implemented on a low-cost FR4 board, the antenna reduced the leakage current formed on coaxial transmission line, due to the advantage of being differentially fed. The second antenna design, fed by coaxial cable (single-ended fed), and without a ground plane, excited only self-balanced modes. The radiation patterns of higher modes in this antenna design are complete and without side lobes. This antenna design also has wide bandwidth characteristics: at 2.4 GHz it had 380 MHz, and at 5.2 GHz it had 1270 MHz bandwidths of high tolerance (stability). The actual measurement validated our simulation results. In the second part, MIMO antennas were designed for 802.11n wireless standards with maximum transfer rates of up to 300 Mbps. First, we designed two small single antennas, which were applied later in MIMO antenna designs. The size of our MIMO antenna designs was only 19 mm ¡Ñ 30.3 mm. In MIMO antenna designs, we employed two methods to increase the isolation between the two MIMO antennas: one manipulated the ground plane size, in which the isolation reached 18.9 dB; the other utilized a decoupling metal, where the overall isolation reached 24.6 dB in all of the operating frequencies, with the best isolation being 31.4 dB. The frequency of the coupling/decoupling for the decoupling metal can be adjusted independently; thus not affecting the original resonant frequency and the return loss of the two MIMO antennas. Actual measurements conducted in the microwave chamber (Reverberation Chamber) have verified the channel capacity were effectively increased, the total radiation efficiencies were about 60%, and the effective diversity gain was about 7dB. The MIMO antenna designs can practically and easily applied in the USB dongles.

Impact hammer is the current modal testing way in Dynapac testing department. Due to highly damped characteristic of big construction machines, there are a few weaknesses for modal testing when using hammer, such as short response time, limited frequency resolution, poor quality of frequency response functions. Therefore, a more advanced excitation equipment is needed to improve the measurement quality. The object for this study is to compare two different measuring methods. The thesis will show a comparison between the hammer testing and the shaker MIMO testing compared with analytical model in a highly damped system. It will also give a reference for further highly damped modal analysis and budgetary assessment to decide the budget expenditure. Result from shaker testing shows a little better correlation than hammer testing compared with FEM model. While the correlation between FEM model and measurement is bad due to many reasons, such as many local modes that can not excited, lack of excitation points, unexpected noise and error from the measurement. While considering the compared results obtained from this machine for now, a simpler structure experiment is suggested to be carried on in the future. Shorter length of stinger can be used to enable higher amplitude of force to excite the property on this machine.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / In this work, the performance of MIMO systems based on space-time coding is investigated through multilinear algebra, more specifically, by means of tensor decompositions, pulling away a bit from commonly used matrix models. We assume a system composed of P transmit and M receive antennas, consisting of a combination of a space-time block code (STBC) with a formatting filter. This filter is formed by a precoding matrix and a matrix that maps the precoded signal onto the transmit antennas. For the considered system, two contributions are presented to solve the problem of channel estimation. First, we propose a tensor-based channel estimation method for orthogonal STBCs in MIMO systems, by focusing on the specific case of the Alamouti scheme. We resort to a third order PARATUCK2 tensor model for the received signal, the third dimension of which is related to the presence of the formatting filter. By capitalizing on this tensor model, a channel estimation method based on the alternating least squares (ALS) algorithm is proposed. As a second contribution, a generalization of this method to an arbitrary nonorthogonal STBC is made, where a generalized structure is proposed for the formatting filter, introducing a fourth dimension into the tensor signal model. In this case, we make use of the PARATUCK(2-4) model followed by its reduction to a structured PARAFAC model, from which a closed-form solution to the channel estimation problem is established. The performance metrics considered for evaluating the proposed channel estimation method are: (I) the quality of the estimation in terms of NMSE and (II) the system reliability in terms of Bit Error Rate. / Neste trabalho, o desempenho de sistemas MIMO baseados em codificaÃÃo espaÃo temporal à investigado via Ãlgebra multilinear, mais especificamente, por meio de decomposiÃÃes tensoriais, afastando-se um pouco dos modelos matriciais comumente adotados. Assume-se um sistema composto de P antenas transmissoras e M receptoras, consistindo de uma combinaÃÃo de um cÃdigo espaÃo-temporal em bloco com um filtro formatador. Esse filtro à formado por uma matriz de prÃ-codificaÃÃo e uma matriz que mapeia os sinais prÃ-codificados nas antenas transmissoras. Para o sistema considerado, duas contribuiÃÃes sÃo apresentadas para solucionar o problema de estimaÃÃo de canal. Primeiro, à proposto um mÃtodo tensorial de estimaÃÃo de canal para STBCs ortogonais em sistemas MIMO, tomando-se como exemplo o esquema de Alamouti. Tal mÃtodo faz uso de um modelo tensorial PARATUCK2 de terceira ordem para o sinal recebido, cuja terceira dimensÃo està associada à presenÃa do filtro formatador. Aproveitando-se desse modelo tensorial, um mÃtodo de estimaÃÃo de canal baseado no algoritmo dos mÃnimos quadrados alternados à proposto. Como uma segunda contribuiÃÃo, uma generalizaÃÃo desse modelo para um STBC nÃo ortogonal arbitrÃrio à feita, em que uma estrutura generalizada à proposta para o filtro formatador, introduzindo uma quarta dimensÃo no modelo tensorial de sinal. Neste caso, faz-se uso do modelo PARATUCK(2-4) seguido pela sua reduÃÃo a um modelo PARAFAC estruturado, a partir do qual uma soluÃÃo em forma fechada para o problema de estimaÃÃo de canal à estabelecida. As mÃtricas de desempenho consideradas para avaliaÃÃo dos mÃtodos de estimaÃÃo de canal propostos sÃo: (I) A qualidade da estimaÃÃo do canal em termos de NMSE e (II) a confiabilidade do sistema em termos de Taxa de Erro de Bit.

Due to the increasing demand and a more complicated environment for signal transmitting, the traditional antenna can hardly satisfy the current technology needs. For a telecommunication service provider, a dual-band integrated antenna array is a good way to reduce cost and increase the capacity since it can operate at different bands. The active part can also achieve beam-forming to adapt to multiple environments. Since two arrays are integrated together, the interface and coupling will be a problem. The performance of the active array is also important since it is supposed to be operated at a complex environment. This thesis will focus on how to achieve better performance of active array and reduce the impact of passive array such as mutual coupling and the change of field distribution of active array. In this thesis project, the limiting factor for the performance of active array is the narrow bandwidth. To solve that, we use another layer of parasitic patch to generate multiple resonances near the fundamental mode. For the passive antenna array, we use crossed-dipole such that the thin wires will block less signal. The return loss result and radiation pattern comparison can show that the bandwidth is broadened with parasitic patches, and the passive array has little influence on the active array. It is a proper way to design a dual-band antenna product with a low budget. / På grund av den ökande efterfrågan och en mer komplicerad miljö för signalsändning kan den traditionella antennen knappast tillfredsställa den nya teknologins behov. För leverantören av telekommunikationstjänster är en integrerad dubbelbandsantennuppsättning ett bra sätt att minska kostnaderna och öka kapaciteten eftersom den kan fungera på olika band. Den aktiva delen kan också uppnå strålformning för att anpassa sig till flera miljöer. Eftersom två arrayer är integrerade tillsammans blir gränssnittet och kopplingen ett problem. Prestandan för en aktiv array är också viktig eftersom den är tänkt att användas i en komplex miljö. Detta examensarbete kommer att fokusera på hur man uppnår bättre prestanda för en aktiv array och minskar effekten av den passiva arrayen. För det här examensarbetet är den främsta faktorn som begränsar prestandan för aktiv array den smala bandbredden. För att lösa detta använder vi ett annat lager av parasitisk patch för att generera flera resonanser nära det grundläggande läget. För passiv antennuppsättning använder vi korsade dipoler så att de tunna ledningarna blockerar mindre av signalen. Jämförelsen av returförlustresultatet och strålningsmönster kan visa att bandbredden breddas med parasitiska patch, och den passiva arrayen har liten inverkan på den aktiva arrayen. Det är ett riktigt sätt att designa en dual-band antennprodukt med en låg budget.

Multiple-Input Multiple-Output (MIMO) systems are a pivotal solution for the significant enhancement of the band-limited wireless channels’ communication capacity. MIMO system is essentially a wireless system with multiple antennas at both the transmitter and receiver ends. Compared to the conventional wireless systems, the main advantages of the MIMO systems are the higher system capacity, more bit rates, more link reliability, and wider coverage area. All of these features are currently considered as crucial performance requirements in wireless communications. Additionally, the emerging new services in wireless applications have created a great motivation to utilize the MIMO systems to fulfil the demands these applications create. The MIMO systems can be combined with other intelligent techniques to achieve these benefits by employing a higher spectral efficiency. The MIMO system design is a multifaceted problem which needs both antenna considerations and baseband signal processing. The performance of the MIMO systems depends on the cross-correlation coefficients between the transmitted/received signals by different antenna elements. Therefore, the Electromagnetic (EM) characteristics of the antenna elements and wireless environment can significantly affect the MIMO system performance. Hence, it is important to include the EM properties of the antenna elements and the physical environment in the MIMO system design and optimizations. In this research, the MIMO system model and system performance are introduced, and the optimum MIMO antenna system is investigated and developed by considering the electromagnetic aspects within three inter-related topics: 1) Fast Numerical Analysis and Optimization of the MIMO Antenna Structures: An efficient and fast optimization method is proposed based on the reciprocity theorem along with the method of moment analysis to minimize the correlation among the received/transmitted signals in MIMO systems. In this method, the effects of the radio package (enclosure) on the MIMO system performance are also included. The proposed optimization method is used in a few practical examples to find the optimal positions and orientations of the antenna elements on the system enclosure in order to minimize the cross-correlation coefficients, leading to an efficient MIMO operation. 2) Analytical Electromagnetic-Theoretic Model for the MIMO Antenna Design: The first requirement for the MIMO antennas is to obtain orthogonal radiation modes in order to achieve uncorrelated signals. Since the Spherical Vector Waves (SVW) form a complete set of orthogonal Eigen-vector functions for the radiated electromagnetic fields, an analytical method based on the SVW approach is developed to excite the orthogonal SVWs to be used as the various orthogonal modes of the MIMO antenna systems. The analytic SVW approach is used to design spherical antennas and to investigate the orthogonality of the radiation modes in the planar antenna structures. 3) Systematic SVW Methodology for the MIMO Antenna Design: Based on the spherical vector waves, a generalized systematic method is proposed for the MIMO antenna design and analysis. The newly developed methodology not only leads to a systematic approach for designing MIMO antennas, but can also be used to determine the fundamental limits and degrees of freedom for designing the optimal antenna elements in terms of the given practical restrictions. The proposed method includes the EM aspects of the antenna elements and the physical environment in the MIMO antenna system, which will provide a general guideline for obtaining the optimal current sources to achieve the orthogonal MIMO modes. The proposed methodology can be employed for any arbitrary physical environment and multi-antenna structures. Without the loss of generality, the SVW approach is employed to design and analyze a few practical examples to show how effective it can be used for MIMO applications. In conclusion, this research addresses the electromagnetic aspects of the antenna analysis, design, and optimization for MIMO applications in a rigorous and systematic manner. Developing such a design and analysis tool significantly contributes to the advancement of high-data-rate wireless communication and to the realistic evaluation of the MIMO antenna system performance by a robust scientifically-based design methodology.