Simulation performance of multiple-input multiple-output systems employing single-carrier modulation and orthogonal frequency division multiplexing

This thesis investigates the simulation performance of multiple-input multiple-output (MIMO) systems utilizing Alamoutibased space-time block coding (STBC) technique. The MIMO communication systems using STBC technique employing both single- carrier modulation and orthogonal frequency division multiplexing (OFDM) are simulated in Matlab. The physical layer part of the IEEE 802.16a standard is used in constructing the simulated OFDM schemes. Stanford University Interim (SUI) channel models are selected for the wireless channel in the simulation process. The performance results of the simulated MIMO systems are compared to those of conventional single antenna systems.http://archive.org/details/simulationperfor109451311Lieutenant Junior Grade, Turkish NavyApproved for public release; distribution is unlimited

Mimo Communication Systems with Reconfigurable Antennas

RÉSUMÉ Les antennes reconfigurables sont capables d'ajuster dynamiquement les caractéristiques de leur diagramme de rayonnement, par exemple, la forme, la direction et la polarisation, en réponse aux conditions environnementales et exigences du système. Ces antennes peuvent aussi être utilisées en conjonction avec des systèmes à entrées multiples sorties multiples (MIMO) pour améliorer davantage la capacité et la fiabilité des systèmes sans fil. Cette thèse étudie certains des problèmes dans les systèmes sans fil équipés d'antennes reconfigurables et propose des solutions pour améliorer la performance du système. Dans les systèmes sans fil utilisant des antennes reconfigurables, la performance atteignable par le système dépend fortement de la connaissance de la direction d'arrivée (DoA) des signaux souhaités et des interférences. Dans la première partie de cette thèse, nous proposons un nouvel algorithme d'estimation de la DoA pour les systèmes à entrer simple et sortie simple (SISO) qui possèdent un élément d'antenne reconfigurable au niveau du récepteur. Contrairement à un système utilisant un réseau d'antennes conventionnelles à diagramme de rayonnement fixe, où la DoA est estimée en utilisant les signaux reçus par plusieurs éléments, dans le réseau d'antennes avec l'algorithme proposé, la DoA est estimée en utilisant des signaux reçus d'un élément d'antenne unique pendant qu'il balai un ensemble de configurations de diagramme de rayonnement. Nous étudions aussi l'impact des différentes caractéristiques des diagrammes de rayonnement utilisés, tels que la largeur du faisceau de l'antenne et le nombre d'étapes de numérisation, sur l'exactitude de la DoA estimée. Dans la deuxième partie de cette thèse, nous proposons un système de MIMO faible complexité employant des antennes reconfigurables sur les canaux sélectifs en fréquence pour atténuer les êtes de trajets multiples et donc éliminer l'interférence entre symboles sans utiliser la technique de modulation multiplexage orthogonale fréquentiel (OFDM). Nous étudions aussi l'impact de la propagation et de l'antenne angulaire largeur de faisceau sur la performance du système proposé et faire la comparaison avec la performance du système MIMO-OFDM. Dans la troisième partie de cette thèse, nous fournissons des outils analytiques pour analyser la performance des systèmes sans _l MIMO équipés d'antennes reconfigurables au niveau du récepteur. Nous dérivons d'abord des expressions analytiques pour le calcul de la matrice de covariance des coefficients des signaux reçus empiétant sur un réseau d'antennes reconfigurables en tenant compte de plusieurs caractéristiques de l'antenne tels que la largeur du faisceau, l'espacement d'antenne, l'angle de pointage ainsi que le gain de l'antenne. Dans cette partie, nous considérons un récepteur MIMO reconfigurable où le diagramme de rayonnement de chaque élément d'antenne dans le réseau peut avoir des caractéristiques différentes. Nous étudions également la capacité d'un système MIMO reconfigurable en utilisant les expressions analytiques dérivées.----------ABSTRACT Reconfigurable antennas are able to dynamically adjust their radiation pattern characteristics, e.g., shape, direction and polarization, in response to environmental conditions and system requirements. These antennas can be used in conjunction with multiple-input multiple-output (MIMO) systems to further enhance the capacity and reliability of wireless networks. This dissertation studies some of the issues in wireless cellular systems equipped with reconfigurable antennas and offer solutions to enhance their performance. In wireless systems employing reconfigurable antennas, the attainable performance improvement highly depends on the knowledge of direction-of-arrival (DoA) of the desired source signals and that of the interferences. In the first part of this dissertation, we propose a novel DoA estimation algorithm for single-input single-output (SISO) system with a reconfigurable antenna element at the receiver. Unlike a conventional antenna array system with fixed radiation pattern where the DoA is estimated using the signals received by multiple elements, in the proposed algorithm, we estimate the DoA using signals collected from a set of radiation pattern states also called scanning steps. We, in addition, investigate the impact of different radiation pattern characteristics such as antenna beamwidth and number of scanning steps on the accuracy of the estimated DoA. In the second part of this dissertation, we propose a low-complexity MIMO system employing reconfigurable antennas over the frequency-selective channels to mitigate multipath effects and therefore remove inter symbol interference without using orthogonal frequency division multiplexing (OFDM) modulation. We study the impact of angular spread and antenna beamwidth on the performance of the proposed system and make comparisons with that of MIMO-OFDM system equipped with omnidirectional antennas. In the third part of this dissertation, we provide an analytical tool to analyze the performance of MIMO wireless systems equipped with reconfigurable antennas at the receiver. We first derive analytical expressions for computing the covariance matrix coefficients of the received signals impinging on a reconfigurable antenna array by taking into account several antenna characteristics such as beamwidth, antenna spacing, antenna pointing angle, and antenna gain. In this part, we consider a reconfigurable MIMO receiver where the radiation pattern of each antenna element in the array can have different characteristics. We, additionally, study the capacity of a reconfigurable MIMO system using the derived analytical expressions

Geometry-based stochastic physical channel modeling for cellular environments

Telecommunication has experienced significant changes over the past few years and its paradigm has moved from wired to wireless communications. The wireless channel constitutes the basic physical link between the transmitter and the receiver antennas. Therefore, complete knowledge of the wireless channel and radio propagation environment is necessary in order to design efficient wireless communication systems. This PhD thesis is devoted to studying the spatial and temporal statistics of the wireless channel in cellular environments based on a geometry-based stochastic physical channel modeling approach. Contributions in this thesis report include the following: • A new physical channel model called the eccentro-scattering model is proposed to study the spatial and temporal statistics of the multipath signals in cellular environments. • Generic closed-form formulas for the probability density function (pdf) of angle of arrival (AoA) and time of arrival (ToA) of the multipath signals in each cellular environment are derived. These formulas can be helpful for the design and evaluation of modern communication systems. • A new Gaussian scattering model is proposed, which consists of two Gaussian functions for the distribution of scatterers around base station (BS) and mobile station (MS) and confines these scatterers within a scattering disc. • The effect of mobile motion on the spatial and temporal statistics of the multipath signals in cellular environments is discussed. Three motion scenarios are considered for the possible trajectory of the mobile unit. Furthermore, two different cases are identified when the terrain and clutter of mobile surrounding have additional effect on the temporal spread of the multipath signals during motion. • The physical channel model is employed to assess the performance of a RAKE receiver in cellular environments. • Comparisons between uniform scattering and Gaussian scattering, which are the two assumptions for the distribution of scatterers usually used in the derivation of the pdf of AoA, are also presented. • An overview of earlier physical channel models and comparisons between these models and with the proposed model are presented