Rate-Optimum Beamforming Transmission in MIMO Rician Fading Channels

Η παρούσα διδακτορική διατριβή επικεντρώνεται στη δυνατότητα που έχουν τα συστήματα ΜΙΜΟ να επιτυγχάνουν υψηλότερη χωρητικότητα από ένα συμβατικά συστήματα SISO. Όμως η χωρητικότητα που επιτυγχάνουν τα συστήματα MIMO σχετίζεται με τη γνώση/πληροφορία την οποία έχουν ο πομπός και ο δέκτης για το κανάλι. Θεωρώντας εργοδικό κανάλι με μιγαδική κανονική κατανομή, στο οποίο ο δέκτης έχει πλήρη γνώση του καναλιού και ο πομπός γνωρίζει μόνο την κατανομή αυτού, επιδιώκεται η μεγιστοποίηση της μέσης αμοιβαία πληροφορίας. Στην περίπτωση εκπομπής beamforming, τη μέγιστη μέση αμοιβαία πληροφορία μεταξύ πομπού-δέκτη επιτυγχάνει ο «βέλτιστος beamformer» και η επιτυγχανόμενη μέγιστη τιμή αναφέρεται ως «εργοδική beamforming χωρητικότητα». Στα πλαίσια της παρούσας διατριβής μελετάται ο τρόπος υπολογισμού του «βέλτιστου beamformer» για την περίπτωση χωρικώς συσχετισμένων καναλιών ΜΙΜΟ με κατανομή Rice και αποδεικνύεται ότι, ο υπόψη υπολογισμός προκύπτει από την επίλυση ενός απλού, μονοδιάστατου (1-Δ) προβλήματος βελτιστοποίησης. Η ανωτέρω απόδειξη βασίζεται σε γεωμετρικές ιδιότητες, κατάλληλους μετασχηματισμούς βάσης και στις συνθήκες Karush-Kuhn-Tucker. Στη συνέχεια υλοποιήθηκε πληθώρα προσομοιώσεων η οποία ανέδειξε την χαμηλή πολυπλοκότητα της προτεινόμενης μονοδιάστατης μεθόδου, καθώς και την υψηλή απόδοση του «βέλτιστου beamformer» ως πολιτική εκπομπής. Επιπρόσθετα, εφαρμόστηκε το μοντέλο προσομοίωσης καναλιών ΜΙΜΟ της 3GPP, με σκοπό την περαιτέρω μελέτη της απόδοσης του «βέλτιστου beamformer» σε πρακτικά λειτουργικά σενάρια. Τα αποτελέσματα επιβεβαίωσαν εκ νέου την υψηλή απόδοση του «βέλτιστου beamformer» και τη σημασία της προτεινόμενης μεθόδου υπολογισμού του.In this doctoral thesis, the focus is on the capability of MIMO systems to achieve much higher capacity than SISO systems. However, the capacity achieved by MIMO systems is closely related to the “channel knowledge” model which is assumed at both ends of the MIMO link. Considering the case of MIMO complex Gaussian ergodic channels, where the receiver has perfect Channel State Information (CSI) whereas the transmitter has Channel Distribution Information (CDIT), we aim at the maximization of the average mutual information between them. For the case of beamforming transmission, the maximum average mutual information is achieved by the “optimum beamformer” and is referred to as “ergodic beamforming capacity”. In this work, the calculation of the optimum beamformer is studied for spatially correlated MIMO Rician fading channels and it is proven that this calculation is achieved by solving a simple 1-D optimization problem. The proof was based on geometrical properties, basis transformations and the Karush-Kuhn-Tucker (KKT) conditions. Extended simulations were performed which demonstrated the low computational complexity of the proposed method as well as the high performance of the optimum beamformer. Additionally the 3GPP MIMO channel model was employed in order to study further the performance of the optimum beamformer in practical operational scenarios. The results confirmed the high performance of the optimum beamformer and the significance of the proposed solutions

On geometry-base statistical channel models for MIMO wireles communications

El uso de sistemas de comunicación de banda ancha de múltiple entradamúltiple salida (Multiple Input Multiple Output MIMO) es actualmente objeto de un interés considerable. Una razón para esto es el reciente desarrollo de sistemas de comunicación móvil de tercera generación (3G) y superiores, tales como la tecnología de banda ancha Wideband Code Division Multiple Access (WCDMA, por sus siglas en inglés), la cual proporciona canales de radio de 5 MHz de ancho de banda. Para el diseño y la simulación de estos sistemas de radio móviles que usan propagación inalámbrica MIMO (como Wideband-CDMA por ejemplo), necesitamos modelos de canal que provean la requerida información espacial y temporal necesaria para el estudio de tales sistemas, esto es, los parámetros básicos de modelado en los dominios del espacio y el tiempo. Como ejemplo podemos mencionar, el valor cuadrático medio de la dispersión del retardo (Delay spread DS) el cual está directamente relacionado a la capacidad de un sistema de comunicación específico y nos da una idea aproximada de la complejidad del receptor. En esta tesis, se propone un modelo basado en geometría con enfoque en grupos (clusters) y es utilizado para el análisis en los dominios del espacio y el tiempo para condiciones estacionarias, y para representar los perfiles de potencia-angulo-retardo (Power Delay Angle Profiles PDAPs) de los componentes multi-trayectoria en ambientes urbanos. Además, se han derivado soluciones en formas cerradas para las expresiones en el dominio del ángulo (espacial) y del tiempo. La investigación previa sobre el modelado de canales cubre una amplia variedad de aspectos en varios niveles de detalle, incluyendo análisis para condiciones no estacionarias. Sin embargo el trabajo presentado en la literatura no incluye las relaciones entre los grupos (cluster) físicos y los PDAPs. El modelo propuesto basado en grupos (clusters) puede ser usado para mejorar aún más el desempeño en condiciones estacionarias de los sistemas de comunicaciones móviles actuales y futuros tales como los sistemas de comunicación MIMO de banda ancha. En la tesis también se presenta un análisis en el dominio del ángulo (espacial) y del tiempo respectivamente, a través de las funciones densidad de probabilidad (PDF) de la dirección de llegada (Direction of Arrival DOA) y el tiempo de llegada (Time of Arrival TOA) para el modelo basado en grupos. A fin de evaluar las funciones de probabilidad teóricas derivadas, éstas han sido comparadas con resultados experimentales publicados en la literatura. La comparación con estos resultados experimentales muestran una buena concordancia, no obstante la técnica de modelado presentada en esta tesis se encuentra limitada a condiciones estacionarias del canal. La condición de no estacionariedad se ubica más allá del alcance de esta tesis, es decir, el modelo propuesto no incorpora el efecto Doppler en los análisis

Interference mitigation using group decoding in multiantenna systems

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MIMO Systems

In recent years, it was realized that the MIMO communication systems seems to be inevitable in accelerated evolution of high data rates applications due to their potential to dramatically increase the spectral efficiency and simultaneously sending individual information to the corresponding users in wireless systems. This book, intends to provide highlights of the current research topics in the field of MIMO system, to offer a snapshot of the recent advances and major issues faced today by the researchers in the MIMO related areas. The book is written by specialists working in universities and research centers all over the world to cover the fundamental principles and main advanced topics on high data rates wireless communications systems over MIMO channels. Moreover, the book has the advantage of providing a collection of applications that are completely independent and self-contained; thus, the interested reader can choose any chapter and skip to another without losing continuity

Cooperative Radio Communications for Green Smart Environments

The demand for mobile connectivity is continuously increasing, and by 2020 Mobile and Wireless Communications will serve not only very dense populations of mobile phones and nomadic computers, but also the expected multiplicity of devices and sensors located in machines, vehicles, health systems and city infrastructures. Future Mobile Networks are then faced with many new scenarios and use cases, which will load the networks with different data traffic patterns, in new or shared spectrum bands, creating new specific requirements. This book addresses both the techniques to model, analyse and optimise the radio links and transmission systems in such scenarios, together with the most advanced radio access, resource management and mobile networking technologies. This text summarises the work performed by more than 500 researchers from more than 120 institutions in Europe, America and Asia, from both academia and industries, within the framework of the COST IC1004 Action on "Cooperative Radio Communications for Green and Smart Environments". The book will have appeal to graduates and researchers in the Radio Communications area, and also to engineers working in the Wireless industry. Topics discussed in this book include: • Radio waves propagation phenomena in diverse urban, indoor, vehicular and body environments• Measurements, characterization, and modelling of radio channels beyond 4G networks• Key issues in Vehicle (V2X) communication• Wireless Body Area Networks, including specific Radio Channel Models for WBANs• Energy efficiency and resource management enhancements in Radio Access Networks• Definitions and models for the virtualised and cloud RAN architectures• Advances on feasible indoor localization and tracking techniques• Recent findings and innovations in antenna systems for communications• Physical Layer Network Coding for next generation wireless systems• Methods and techniques for MIMO Over the Air (OTA) testin

Cooperative Radio Communications for Green Smart Environments

The demand for mobile connectivity is continuously increasing, and by 2020 Mobile and Wireless Communications will serve not only very dense populations of mobile phones and nomadic computers, but also the expected multiplicity of devices and sensors located in machines, vehicles, health systems and city infrastructures. Future Mobile Networks are then faced with many new scenarios and use cases, which will load the networks with different data traffic patterns, in new or shared spectrum bands, creating new specific requirements. This book addresses both the techniques to model, analyse and optimise the radio links and transmission systems in such scenarios, together with the most advanced radio access, resource management and mobile networking technologies. This text summarises the work performed by more than 500 researchers from more than 120 institutions in Europe, America and Asia, from both academia and industries, within the framework of the COST IC1004 Action on "Cooperative Radio Communications for Green and Smart Environments". The book will have appeal to graduates and researchers in the Radio Communications area, and also to engineers working in the Wireless industry. Topics discussed in this book include: • Radio waves propagation phenomena in diverse urban, indoor, vehicular and body environments• Measurements, characterization, and modelling of radio channels beyond 4G networks• Key issues in Vehicle (V2X) communication• Wireless Body Area Networks, including specific Radio Channel Models for WBANs• Energy efficiency and resource management enhancements in Radio Access Networks• Definitions and models for the virtualised and cloud RAN architectures• Advances on feasible indoor localization and tracking techniques• Recent findings and innovations in antenna systems for communications• Physical Layer Network Coding for next generation wireless systems• Methods and techniques for MIMO Over the Air (OTA) testin