In order to support the new paradigm shift in fifth generation (5G) mobile communication, radically different network architectures, associated technologies and network operation algorithms, need to be developed compared to existing fourth generation (4G) cellular solutions. The evolution toward 5G mobile networks will be characterized by an increasing number of wireless devices, increasing device and service complexity, and the requirement to access mobile services ubiquitously. To realise the dramatic increase in data rates in particular, research is focused on improving the capacity of current, Long Term Evolution (LTE)-based, 4G network standards, before radical changes are exploited which could include acquiring additional spectrum. The LTE network has a reuse factor of one; hence neighbouring cells/sectors use the same spectrum, therefore making the cell-edge users vulnerable to heavy inter cell interference in addition to the other factors such as fading and path-loss. In this direction, this thesis focuses on improving the performance of cell-edge users in LTE and LTE-Advanced networks by initially implementing a new Coordinated Multi-Point (CoMP) technique to support future 5G networks using smart antennas to mitigate cell-edge user interference in uplink. Successively a novel cooperative uplink inter-cell interference mitigation algorithm based on joint reception at the base station using receiver adaptive beamforming is investigated. Subsequently interference mitigation in a heterogeneous environment for inter Device-to-Device (D2D) communication underlaying cellular network is investigated as the enabling technology for maximising resource block (RB) utilisation in emerging 5G networks. The proximity of users in a network, achieving higher data rates with maximum RB utilisation (as the technology reuses the cellular RB simultaneously), while taking some load off the evolved Node B (eNodeB) i.e. by direct communication between User Equipment (UE), has been explored. Simulation results show that the proximity and transmission power of D2D transmission yields high performance gains for D2D receivers, which was demonstrated to be better than that of cellular UEs with better channel conditions or in close proximity to the eNodeB in the network. It is finally demonstrated that the application, as an extension to the above, of a novel receiver beamforming technique to reduce interference from D2D users, can further enhance network performance. To be able to develop the aforementioned technologies and evaluate the performance of new algorithms in emerging network scenarios, a beyond the-state-of-the-art LTE system-level-simulator (SLS) was implemented. The new simulator includes Multiple-Input Multiple-Output (MIMO) antenna functionalities, comprehensive channel models (such as Wireless World initiative New Radio II i.e. WINNER II) and adaptive modulation and coding schemes to accurately emulate the LTE and LTE-A network standards.

Millimeter wave technologies present an appealing solution for increasing data throughputs as they provide abundant contiguous channel bandwidths as compared to conventional microwave networks. However, millimeter wave technologies suffer from severe propagation limitations and channel impairments such as atmospheric attenuation and absorption, path and penetration losses, and blockage sensitivity. Therefore, phased arrays and beamforming technologies are necessary to compensate for the degraded signal levels due to the aforementioned factors. Namely, base stations and mobile stations utilize directional transmission in the control- and data- plane for an enhanced channel capacity, which results in initial access challenges due to the absence of omni-directional transmission. Here the base station and mobile station are compelled to exhaustively search the entire spatial domain, i.e., in order to determine the best beamforming and combining vectors that yield the highest received signal level. Overall, a wide range of studies have looked at the initial beam access challenges in millimeter wave networks, with most efforts focusing on iterative and exhaustive search procedures, as well as subarrays schemes and out-of-band beam access. However, these studies suffer from significant signaling overhead attributed to the prolonged beam scanning cycle. In particular, access times here are excessively high that exceed control plane latencies and coherence times. Furthermore, existing work suffer from high computational complexity, power consumption, energy inefficiency, as well as low directivities and high outage probabilities. In light of the above, the contributions in this dissertation propose fast initial beam access schemes based upon novel meta-heuristic search schemes and beamforming architectures. These contributions include modified search procedures inspired by Nelder Mead, Luss-Jaakola, divide-and-conquer with Tabu search, generalized pattern search, and Hooke Jeeves methods. Furthermore, efficient and highly-directive access schemes are also developed in this dissertation levering sidelobe emissions, grating lobes and Hamming codes. The overall performance of the proposed solutions here is extensively evaluated versus traditional access schemes and incorporating different channel and path loss models. Finally, this dissertation addresses the problem of link sensitivity and blockage effects in millimeter wave networks, a subsequent stage to beam access and link association. Nevertheless, a novel link recovery procedure is proposed here that features instantaneous link-recovery and high signal levels.

La facilité de déploiement et la flexibilité des technologies sans fil ont permis une évolution considérable des normes IEEE 802.11. L'arrivée de la fibre optique à la maison a également motivé des études de recherche pour accroître les débits et la capacité. Dans ce contexte, la dernière norme IEEE 802.11ac ratifiée en 2014 a normalisé de nouvelles technologies pour atteindre des débits maximaux au-dessus de 1Obit/s. En particulier, 802 llac propose le Multiple Input Multiple Output Multi-Utilisateurs (MIMO-MU) et le Transmit Beamforming (TxBF). Ces technologies d'antennes intelligentes supposent un diagramme d'antenne d'émission qui dépend de la position des utilisateurs et des caractéristiques du canal de propagation multi-trajets correspondant. Cependant, les outils d'ingénierie et de planification radio actuels simulent une carte de couverture fixe et indépendante de tout traitement d'antennes adaptatives côté émission. Cette thèse étudie l'impact de ces techniques MIMO-MU et TxBF et propose des solutions adaptées pour l'ingénierie radio et l'optimisation du système ainsi que pour les outils de planification radio. En effet, la première partie de cette thèse consiste à affiner les gains de capacité en identifiant les configurations et les paramètres système optimaux. La deuxième partie aborde les gains de beamforming en termes du gain sur le rapport signal à bruit (SNR) et sur la réduction du niveau d'interférence pour avoir une modélisation réaliste de la couverture radio. / The deployment facility and flexibility of wireless technologies have allowed considerable evolution of IEEE 802 .11 standards. The arrival of the optical fiber to the home has further motivated the research studies to increase data rates and capacity. ln this context, the latest IEEE 802.l lac standard ratified in 2014 proposes new technologies to achieve maximum data rates above 1 Gbit/s. ln particular, 802.l lac includes the Multi-User Multiple Input Multiple Output (MU-MIMO) and Transmit Beamforming (TxBF). These smart antenna technologies assume a variable transmit antenna pattern in function of the users' position and the corresponding multipath propagation channel characteristics. However, the actual radio planning tools give a fixed coverage map in dependent of any adaptive or smart antenna processing. This thesis studies the impact of the MU-MIMO and TxBF techniques on radio engineering, system optimization as well as radio planning tools. Indeed, the first part of this thesis deals with refining the sum rate capacity gains by identifying interesting system configurations and optimal system parameters. The second part addresses the beamforming gains in terms of the Signal-to-Noise Ratio (SNR) gain and interference level to have realistic radio coverage modeling.

L'imagerie ultrasonore (US) permet de réaliser des examens médicaux non invasifs avec des méthodes d'acquisition rapides à des coûts modérés. L'imagerie cardiaque, abdominale, fœtale, ou mammaire sont quelques-unes des applications où elle est largement utilisée comme outil de diagnostic. En imagerie US classique, des ondes acoustiques sont transmises à une région d'intérêt du corps humain. Les signaux d'écho rétrodiffusés, sont ensuite formés pour créer des lignes radiofréquences. La formation de voies (FV) joue un rôle clé dans l'obtention des images US, car elle influence la résolution et le contraste de l'image finale. L'objectif de ce travail est de modéliser la formation de voies comme un problème inverse liant les données brutes aux signaux RF. Le modèle de formation de voies proposé ici améliore le contraste et la résolution spatiale des images échographiques par rapport aux techniques de FV existants. Dans un premier temps, nous nous sommes concentrés sur des méthodes de FV en imagerie US. Nous avons brièvement passé en revue les techniques de formation de voies les plus courantes, en commencent par la méthode par retard et somme standard puis en utilisant les techniques de formation de voies adaptatives. Ensuite, nous avons étudié l'utilisation de signaux qui exploitent une représentation parcimonieuse de l'image US dans le cadre de la formation de voies. Les approches proposées détectent les réflecteurs forts du milieu sur la base de critères bayésiens. Nous avons finalement développé une nouvelle façon d'aborder la formation de voies en imagerie US, en la formulant comme un problème inverse linéaire liant les échos réfléchis au signal final. L'intérêt majeur de notre approche est la flexibilité dans le choix des hypothèses statistiques sur le signal avant la formation de voies et sa robustesse dans à un nombre réduit d'émissions. Finalement, nous présentons une nouvelle méthode de formation de voies pour l'imagerie US basée sur l'utilisation de caractéristique statistique des signaux supposée alpha-stable. / Ultrasound (US) allows non-invasive and ultra-high frame rate imaging procedures at reduced costs. Cardiac, abdominal, fetal, and breast imaging are some of the applications where it is extensively used as diagnostic tool. In a classical US scanning process, short acoustic pulses are transmitted through the region-of-interest of the human body. The backscattered echo signals are then beamformed for creating radiofrequency(RF) lines. Beamforming (BF) plays a key role in US image formation, influencing the resolution and the contrast of final image. The objective of this thesis is to model BF as an inverse problem, relating the raw channel data to the signals to be recovered. The proposed BF framework improves the contrast and the spatial resolution of the US images, compared with the existing BF methods. To begin with, we investigated the existing BF methods in medical US imaging. We briefly review the most common BF techniques, starting with the standard delay-and-sum BF method and emerging to the most known adaptive BF techniques, such as minimum variance BF. Afterwards, we investigated the use of sparse priors in creating original two-dimensional beamforming methods for ultrasound imaging. The proposed approaches detect the strong reflectors from the scanned medium based on the well-known Bayesian Information Criteria used in statistical modeling. Furthermore, we propose a new way of addressing the BF in US imaging, by formulating it as a linear inverse problem relating the reflected echoes to the signal to be recovered. Our approach offers flexibility in the choice of statistical assumptions on the signal to be beamformed and it is robust to a reduced number of pulse emissions. At the end of this research, we investigated the use of the non-Gaussianity properties of the RF signals in the BF process, by assuming alpha-stable statistics of US images.

Massive multiple-input multiple-output is a promising technique for the next generation of wireless communication systems which addresses most of the critical challenges associated with concurrent relaying systems, such as digital signal processing complexity, long processing delay, and low latency wireless communications. However, the deployment of conventional fully digital beamforming methods, dedicates one radio frequency (RF) chain to each antenna, is not viable enough due to the high fabrication/implementation cost and power consumption. In this thesis, we envision to address this critical issue by reducing the number of RF chains in a viable analog/digital configuration paradigm which is usually referred to hybrid structure. From another viewpoint, the development of fifth generation enabling technologies brings new challenges to the design of power amplifiers (PAs). In particular, there is a strong demand for low-cost, nonlinear PAs which, however, introduce nonlinear distortions. On the other hand, contemporary expensive PAs show great power efficiency in their nonlinear region. Inspired by this trade-off between nonlinearity distortions and efficiency, finding an optimal operating point is highly desirable, and this is the second key contribution of this thesis.

abstract: This thesis report aims at introducing the background of QR decomposition and its application. QR decomposition using Givens rotations is a efficient method to prevent directly matrix inverse in solving least square minimization problem, which is a typical approach for weight calculation in adaptive beamforming. Furthermore, this thesis introduces Givens rotations algorithm and two general VLSI (very large scale integrated circuit) architectures namely triangular systolic array and linear systolic array for numerically QR decomposition. To fulfill the goal, a 4 input channels triangular systolic array with 16 bits fixed-point format and a 5 input channels linear systolic array are implemented on FPGA (Field programmable gate array). The final result shows that the estimated clock frequencies of 65 MHz and 135 MHz on post-place and route static timing report could be achieved using Xilinx Virtex 6 xc6vlx240t chip. Meanwhile, this report proposes a new method to test the dynamic range of QR-D. The dynamic range of the both architectures can be achieved around 110dB. / Dissertation/Thesis / M.S. Electrical Engineering 2014

Abstract Advanced multiple-input multiple-output (MIMO) transceiver structures which utilize the knowledge of channel state information (CSI) at the transmitter side to optimize certain link parameters (e.g., throughput, fairness, spectral efficiency, etc.) under different constraints (e.g., maximum transmitted power, minimum quality of services (QoS), etc.) are considered in this thesis. Adaptive transmission schemes for point-to-point MIMO systems are considered first. A robust link adaptation method for time-division duplex systems employing MIMO-OFDM channel eigenmode based transmission is developed. A low complexity bit and power loading algorithm which requires low signaling overhead is proposed. Two algorithms for computing the sum-capacity of MIMO downlink channels with full CSI knowledge are derived. The first one is based on the iterative waterfilling method. The convergence of the algorithm is proved analytically and the computer simulations show that the algorithm converges faster than the earlier variants of sum power constrained iterative waterfilling algorithms. The second algorithm is based on the dual decomposition method. By tracking the instantaneous error in the inner loop, a faster version is developed. The problem of linear transceiver design in MIMO downlink channels is considered for a case when the full CSI of scheduled users only is available at the transmitter. General methods for joint power control and linear transmit and receive beamformers design are provided. The proposed algorithms can handle multiple antennas at the base station and at the mobile terminals with an arbitrary number of data streams per scheduled user. The optimization criteria are fairly general and include sum power minimization under the minimum signal-to-interference-plus-noise ratio (SINR) constraint per data stream, the balancing of SINR values among data streams, minimum SINR maximization, weighted sum-rate maximization, and weighted sum mean square error minimization. Besides the traditional sum power constraint on the transmit beamformers, multiple sum power constraints can be imposed on arbitrary subsets of the transmit antennas.This extends the applicability of the results to novel system architectures, such as cooperative base station transmission using distributed MIMO antennas. By imposing per antenna power constraints, issues related to the linearity of the power amplifiers can be handled as well. The original linear transceiver design problems are decomposed as a series of remarkably simpler optimization problems which can be efficiently solved by using standard convex optimization techniques. The advantage of this approach is that it can be easily extended to accommodate various supplementary constraints such as upper and/or lower bounds for the SINR values and guaranteed QoS for different subsets of users. The ability to handle transceiver optimization problems where a network-centric objective (e.g., aggregate throughput or transmitted power) is optimized subject to user-centric constraints (e.g., minimum QoS requirements) is an important feature which must be supported by future broadband communication systems.

This thesis addresses radiation pattern synthesis problems for small linear periodic phased arrays (with array elements less then 10). Due to the small array size conventional pattern synthesis techniques fail to produce the required results. In the case of practical small arrays, mutual coupling and element pattern asymmetric effect degrade the array radiation performance. The main performance metrics considered in this thesis include side lobe level (SLL), gain, halfpower beamwidth (HPBW) and mainbeam scan direction. The conventional pattern synthesis approaches result in sub optimal gain, SLL and HPBW due to the limited number of elements and the mutual coupling involved. In case of difference pattern synthesis these factors resulted in lower difference pattern slope, degraded SLL and difference peak asymmetry. The sum and difference patterns are used in monopulse arrays and a simplified feed that could produce both patterns with acceptable radiation properties is of interest and has been examined (chapter 5). A conventional technique is applied to small arrays to synthesise a sector beam and there is limited control over the radiation pattern. It is shown that the mutual coupling has significant effect on the array radiation pattern and mitigation is necessary for optimum performance (chapter 6). Furthermore, wideband phased arrays may have a natural limitation of the HPBW in low gain applications and minimisation of the variation becomes important. Also the SLL variations for wideband antenna arrays in the presence of mutual coupling considerably degrade the radiation pattern. The mutual coupling degrades significantly the radiation pattern performance in case of small scanning wideband arrays (chapter 7). It is the primary goal of this thesis to develop an optimisation scheme thatis applied in the above scenarios (chapters 3 & 4). The only degree of freedom assumed is the array excitation. Optimised amplitude and phase for each element in the array are determined by the proposed scheme, concurrently. The deterministic optimisation techniques reported in the literature for the pattern synthesis may involve complicated problem modelling. The heuristic opti-misation techniques generally are computationally expensive. The proposedIntelligent z-space Boundary Condition-Particle Swarm Optimiser (IzBC-PSO)is based on a heuristic algorithm. This scheme can be applied to a wider rangeof problems without significant modifications and requires fewer computationscompared to the competing techniques.In order to verify the performance of IzBC-PSO antenna array measure-ments were performed in the receiving mode only using the online and offlinedigital beamforming setups described in chapter 8. The measurement resultsshow that the proposed scheme may be successfully applied with both onlineand offline digital beamformers for a practical small array (chapter 8).

Esta tesis doctoral aborda el estudio y análisis de la acústica de salas mediante un proceso de descomposición del campo sonoro muestreado con arrays circulares de micrófonos. El comportamiento acústico de una sala teniendo en cuenta todos los factores espaciales no es algo trivial. Este problema es conocido desde la antigüedad: griegos y romanos comenzaron a cuidar las cualidades acústicas en sus construcciones arquitectónicas basándose principalmente en diseños puramente prácticos. Más tarde sería el físico Sabine y su modelo estadístico para la medida del tiempo de reverberación de salas en que daría lugar al análisis moderno de la acústica arquitectónica. En la actualidad existen múltiples y avanzados métodos de análisis basados en el estudio de las respuestas al impulso de las salas capturadas mediante la utilización de fuentes de sonido y micrófonos de precisión que han contribuido a nuevos avances y mejoras dentro de este campo de la acústica. Los métodos mas modernos propuestos recientemente utlizan arrays de micrófonos para intentar capturar el campo de forma más precisa y con todas sus características espaciales, sin embargo todavía no han sido explotados convenientemente para obtener conclusiones significativas y relevantes sobre la acústica final de salas y sus aspectos geométricos. En esta tesis se lleva a cabo una metodología de análisis de salas basada en técnicas de descomposición de onda plana y de beamforming modal. Mediante la construcción de un array circular con micrófonos cardioides, así como de la implementación de un algoritmo de deteccion de máximos locales en ecogramas basado en morfología de imagen, se obtienen, analizan y comparan la acústica de las salas (reflexiones, absorciones, etc) permitiendo extrapolar una serie de conclusiones sobre sus características, comportamiento y calidad. Los resultados obtenidos por ambos métodos de análisis se comparan para identificar las reflexiones más significativas de las salas extrayendo informaci / Torres Aranda, AM. (2012). ANÁLISIS DE LA ACÚSTICA DE SALAS MEDIANTE LA UTILIZACIÓN DE ARRAYS DE MICRÓFONOS CIRCULARES [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/18221 / Palancia

In this work we propose the apodization or windowing of the coupling coefficients of the unit cells conforming a coupled resonator device as a mean to reduce the level of secondary sidelobes in the case of SCISSOR configuration [7] or reducing the passband ripples in the case of CROW configuration [8]. This technique is regularly employed in the design of digital filters [18] and has been applied as well in the design of other photonic devices such as corrugated waveguide filters [9] and fiber Bragg gratings [19]. We also propose a novel technique for the apodization of coupled resonator structures by applying a longitudinal offset between resonators in order to modify the power coupling constant, which alleviates the technical requirements required for the production of these devices. We will demonstrate the design, fabrication and characterization of CROW structures employing the apodization through the aforementioned technique. / Doménech Gómez, JD. (2013). Apodized Coupled Resonator Optical Waveguides: Theory, design and characterization [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/32278 / TESIS