Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Laskar, Joy; Committee Member: Chang, Jae Joon; Committee Member: Cressler, John D.; Committee Member: Kornegay, Kevin T.; Committee Member: Lee, Chang-Ho; Committee Member: Tentzeris, Manos M.. Part of the SMARTech Electronic Thesis and Dissertation Collection.

abstract: Demands in file size and transfer rates for consumer-orientated products have escalated in recent times. This is primarily due to the emergence of high definition video content. Now factor in the consumer desire for convenience, and we find that wireless service is the most desired approach for inter-connectivity. Consumers expect wireless service to emulate wired service with little to virtually no difference in quality of service (QoS). The background section of this document examines the QoS requirements for wireless connectivity of high definition video applications. I then proceed to look at proposed solutions at the physical (PHY) and the media access control (MAC) layers as well as cross-layer schemes. These schemes are subsequently are evaluated in terms of usefulness in a multi-gigabit, 60 GHz wireless multimedia system targeting the average consumer. It is determined that a substantial gap in published literature exists pertinent to this application. Specifically, little or no work has been found that shows how an adaptive PHYMAC cross-layer solution that provides real-time compensation for varying channel conditions might be actually implemented. Further, no work has been found that shows results of such a model. This research proposes, develops and implements in Matlab code an alternate cross-layer solution that will provide acceptable QoS service for multimedia applications. Simulations using actual high definition video sequences are used to test the proposed solution. Results based on the average PSNR metric show that a quasi-adaptive algorithm provides greater than 7 dB of improvement over a non-adaptive approach while a fully-adaptive alogrithm provides over18 dB of improvement. The fully adaptive implementation has been conclusively shown to be superior to non-adaptive techniques and sufficiently superior to even quasi-adaptive algorithms. / Dissertation/Thesis / M.S. Engineering 2011

Doctor of Philosophy / Department of Electrical and Computer Engineering / Balasubramaniam Natarajan / Triggered by the popularity of smart devices, wireless traffic volume and device connectivity have been growing exponentially during recent years. The next generation of wireless networks, i.e., 5G, is a promising solution to satisfy the increasing data demand through combination of key enabling technologies such as deployment of a high density of access points (APs), referred to as ultra-densification, and utilization of a large amount of bandwidth in millimeter wave (mmWave) bands. However, due to unfavorable propagation characteristics, this portion of spectrum has been under-utilized. As a solution, large antenna arrays that coherently direct the beams will help overcome the hostile characteristics of mmWave signals. Building networks of directional antennas has given rise to many challenges in wireless communication design. One of the main challenges is how to incorporate 5G technology into current networks and design uniform structures that bring about higher network performance and quality of service. In addition, the other factor that can be severely impacted is interference behavior. This is basically due to the fact that, narrow beams are highly vulnerable to obstacles in the environment. Motivated by these factors, the present dissertation addresses some key challenges associated with the utilization of mmWave signals. As a first step towards this objective, we first propose a framework of how 5G mmWave access points can be integrated into the current wireless structures and offer higher data rates. The related resource sharing problem has been also proposed and solved, within such a framework. Secondly, to better understand and quantify the interference behavior, we propose interference models for mmWave networks with directional beams for both large scale and finite-sized network dimension. The interference model is based on our proposed blockage model which captures the average number of obstacles that cause a complete link blockage, given a specific signal beamwidth. The main insight from our analysis shows that considering the effect of blockages leads to a different interference profile. Furthermore, we investigate how to model interference considering not only physical layer specifications but also upper layers constraints. In fact, upper network layers, such as medium access control (MAC) protocol controls the number of terminals transmitting simultaneously and how resources are shared among them, which in turn impacts the interference power level. An interesting result from this analysis is that, from the receiving terminal standpoint, even in mmWave networks with directional signals and high attenuation effects, we still need to maintain some sort of sensing where all terminals are not allowed to transmit their packets, simultaneously. The level of such sensing depends on the terminal density. Lastly, we provide a framework to detect the network regime and its relation to various key deployment parameters, leveraging the proposed interference and blockage models. Such regime detection is important from a network management and design perspective. Based on our finding, mmWave networks can exhibit either an interference-limited regime or a noise-limited regime, depending on various factors such as access point density, blockage density, signal beamwidth, etc.

L'évolution des nœuds technologiques dans l'industrie des semi-conducteurs se traduit de nos jours, dans le domaine des radiofréquences, par une miniaturisation des front-ends et une amélioration des performances électriques des émetteurs-récepteurs à des fréquences de plus en plus hautes. Cette évolution a conduit à la diversification des applications en bandes millimétriques (30 – 300 GHz) dans les secteurs des télécommunications, du divertissement multimédia, de l'automobile et de la sécurité. Plus particulièrement, le secteur des télécommunications connaît aujourd'hui une réelle révolution avec la création de nouveaux standards pour les liens sans-fil millimétriques à courte portée (comme WiGiG et IEEE 802.11ad) et l'apparition de nouvelles architectures basées sur des liaisons point-à-point qui constitueront dans les prochaines années la colonne vertébrale de la cinquième génération des réseaux mobiles. Dans le cadre de ces travaux de thèse, un intérêt particulier sera porté sur les modules intégrés sans fils et à faible consommation opérant dans la bande 57 – 66 GHz (dite généralement 60 GHz). A ces fréquences, la longueur d'onde en espace libre est comparable aux dimensions caractéristiques des boitiers standards utilisés pour l'encapsulation des transceivers. Il devient donc envisageable d'intégrer les antennes ainsi que d'autres composants passifs directement dans l'empilement technologique du circuit ou dans le boitier. Cette nouvelle génération de dispositifs électroniques, destinés au marché des terminaux portables, introduit de nouveaux défis en termes de performances électriques, de fiabilité mécanique, de coût et de possibilités d'industrialisation. Le packaging microélectronique joue dans ce cas un rôle principal dans la définition des performances globales du système qui s'étend au-delà de la simple protection de circuits intégrés pour couvrir d'autres fonctions d'intégration de divers dispositifs actifs et passifs. L'axe principal d'étude adopté ici porte sur le packaging d'un module SiP (System-in-Package) intégré en 3D et réalisé en technologie interposer silicium. Le mémoire de thèse s'articule en quatre chapitres : Le premier chapitre donne dans un premier temps une brève introduction aux bandes millimétriques et aux conditions de propagation spécifiques à ces bandes avant de présenter des exemples d'applications relevant de divers domaines civils et militaires. Ensuite, nous dressons un état de l'art des modules SiP millimétriques intégrés selon différentes approches technologiques. Le second chapitre est consacré à l'étude d'un module 60 GHz intégré sur silicium haute-résistivité en technologie interposer silicium. Nous nous intéressons aux méthodes de caractérisation adaptées aux diverses briques technologiques du back-end silicium spécifique aux applications RF-millimétriques et notamment les interconnexions, les matériaux diélectriques ainsi que les antennes intégrées. La caractérisation inclut également un test d'émission-réception entre deux modules 60 GHz. Dans le troisième chapitre, nous proposons d'améliorer le module grâce à un nouveau design d'antennes utilisant le concept de Surface Haute-Impédance (SHI). Ce design est destiné à octroyer plus de compacité et plus de fiabilité au module tout en conservant ses performances électriques. Finalement, le quatrième chapitre détaille les étapes de fabrication du véhicule de test antennaire ainsi que des résultats de caractérisation des antennes et des nouveaux matériaux diélectriques utilisés pour l'empilement technologique. / The evolution of semi-conductor technology nodes has led to a significant miniaturization of today's RF front-ends and to the enhancement of the electrical performance of transceivers at higher frequencies. This leads to the diversification of RF/millimeter-wave (30 – 300 GHz) applications in the fields of telecommunications, multimedia entertainment, automotive and security. More specifically, telecommunications are going through a real revolution with the creation of new standards (such as WiGiG and IEEE 802.11ad) and the introduction of new network architectures based on point-to-point links as the backbone of the 5th generation of mobile networks. In this PhD work, we will focus on integrated wireless and low consumption modules operating in the 57 – 66 GHz band (generally designated as the 60 GHz band). At these frequencies, the free-space wavelength is comparable to the characteristic dimensions of most standard transceiver packages. This opens an opportunity to integrate the antennas as well as other passive components directly to the metal/dielectric stack or in the package. This new generation of electronic devices which are dedicated to the nomad terminal market brings new challenges in terms of electrical performance, mechanical reliability, cost and manufacturability. Microelectronic packaging plays in this case a key role in defining the global performance of the system. Its functions extend beyond the protection of the IC and cover other schemes with opportunities to integrate passive and active devices. This work focuses on the study of an SiP module (System-in-Package) featuring 3D integration on Silicon interposer. The dissertation comprises four chapters and is structured as follows: In the first chapter, a brief introduction of millimeter-waves and their propagation conditions is given. Then, examples of current and emerging civilian and military applications are addressed. State of the art of SiP/mmW modules is then presented according to different technology approaches proposed by industrial and academic contributors. The second chapter is dedicated to the study of a 60 GHz integrated module on a high-resistivity silicon interposer chip. We focus on electrical characterization methods which are adapted to different building blocks of the silicon back-end technology. These include interconnects, dielectrics and integrated antennas. The characterization steps also include full-scale and standard-compliant tests of two communicating 60 GHz modules. In the third chapter, we propose to improve the existing module with a novel antenna design based on a High-Impedance Surface (HIS) reflector. This design is intended to bring more compactness and higher reliability to the original one while conserving the overall electrical performance. Finally, the fourth chapter deals with the fabrications and experimental validation of the antenna test vehicle as well as the wideband characterization of the dielectrics used for the new stack.

L’émergence des nouvelles applications et services mobiles, nécessitant de plus en plus de débits de communications, contribue à une explosion massive du trafic de données au sein du réseau. Pour faire face à ce challenge, les systèmes millimétriques sont une des technologies identifiées pour les futurs réseaux 5G en raison de la bande passante accrue disponible dans cette plage du spectre. Toutefois, pour tirer pleinement profit de tels systèmes, la connaissance des caractéristiques liées à la propagation des ondes radio dans ces bandes de fréquence est primordiale. Ainsi, dans cette thèse, l’attention est portée sur l’évaluation de la dépendance en fréquence des caractéristiques principales du canal de propagation, généralement décrites par les paramètres dits « large scale parameters (LSPs) ». Ceux–ci incluent les pertes de pénétration, l’étalement temporel ou angulaire du canal et l’affaiblissement moyen du canal. Les études sont basées sur des campagnes de mesures réalisées à Belfort, dans des scénarios de déploiement 5G typiques comme la pénétration à l’intérieur des bâtiments et la propagation en milieu urbain extérieur, entre 3 et 60 GHz. / The advent of bandwidth–demanding mobile applications and services has led to a massive explosion of the network data traffic. In order to alleviate this issue, millimeter–Wave communications systems are a promising technology for future 5G systems thanks to the large amount of bandwidth available in this frequency range. However, in order to take full advantage of this technology, knowledge of the radio propagation channel characteristics in these frequency bands is paramount. Therefore, in this thesis, the objective is to study the frequency–dependence of the propagation channel large scale parameters (LSPs), which describe the main channel characteristics. These LSPs include the building penetration losses, the channel delay spread, the channel azimuth spread and the propagation path–loss. The studies are performed thanks to measurement campaigns conducted in Belfort, in typical 5G deployment scenarios such as outdoor–to–indoor and urban outdoor environments, between 3 and 60 GHz.

京都大学 / 新制・課程博士 / 博士(情報学) / 甲第23329号 / 情博第765号 / 新制||情||130(附属図書館) / 京都大学大学院情報学研究科通信情報システム専攻 / (主査)教授 守倉 正博, 教授 原田 博司, 教授 大木 英司 / 学位規則第4条第1項該当 / Doctor of Informatics / Kyoto University / DFAM

<div>Mobile devices operating at millimeter-wave (mmWave) frequencies are expected to comprise an integral part of fifth generation (5G) communication systems to meet increasing data rate demands. Massive multiple-input multiple-output (MIMO) and advanced signal processing techniques are required to overcome the harsh propagation environment in this spectrum. We focus on two aspects of MIMO communication systems. </div><div><br></div><div>First, the large number of antennas creates a challenge in aligning and tracking highly directional, narrow beams. Algorithms which rapidly adapt to the changing mobile environment are required. We propose a novel beam alignment and tracking algorithm for time-varying, sparse mmWave channels using multi-armed bandit beam selection. We show our algorithm has a more rapid initial beam alignment compared to other beam selection policies and, for dynamic channel support, long-term beamforming gain commensurate to omni-directional channel training. Simulation results are accomplished using idealized and realistic mmWave channel models.</div><div><br></div><div>Second, massive MIMO systems can generate potentially prohibitive amounts of data due to the large numbers of antennas. With modern parallel, low-rate analog-to-digital converters (ADCs), the bottleneck is often not in the quantization of the received signals but, rather, in the processing of the digitized bits. Therefore, we develop an adaptive algorithm for down-selecting the digital output data to meet some required output data rate threshold while simultaneously maximizing the information between the transmitted signal and the selected output.</div>

Millimeter wave (mmWave) spectrum above 30 GHz offers us an opportunity to pursue high-data-rate transmission using a channel bandwidth up to several gigahertz. To provide reliable link quality in mmWave frequency bands, hybrid analog-digital beamforming plays a crucial role in overcoming severe path loss and, meanwhile, satisfies the demand for low-power-consumption radio frequency (RF) devices. Implementing hybrid beamforming based on available channel state information (CSI) is a common solution in the hybrid beamforming literature. However, many reference methods underestimate the computational complexity of channel estimation for large antenna arrays or subsequent steps, such as the singular value decomposition of a channel matrix. To this end, we present a low-complexity scheme that exploits implicit channel knowledge to facilitate the design of hybrid beamforming for frequency-selective fading channels. We start from the study of channel estimation using the orthogonal matching pursuit (OMP) algorithm and realize that the problems of channel estimation and analog beam selection are equivalent if the candidates for analog beamforming vectors in the codebooks are mutually orthogonal. This implies that when orthogonal codebooks are employed, the observations used in channel estimation for large antenna arrays can be used to implement hybrid beamforming directly. The above-mentioned observations can be regarded as \textbf{implicit CSI}; they are coupling coefficients of all possible pairs of analog beamforming vectors on both sides of the channel. The idea of using implicit CSI to implement hybrid beamforming is further extended to the cases of non-orthogonal codebooks. Instead of calculating the mutual information between the transmitter and receiver, we focus on small-size coupling matrices between beam patterns selected by using appropriate key parameters as performance indicators. Therefore, the proposed hybrid beamforming method becomes much simpler: it amounts to collecting different sets of large-power coupling coefficients to construct multiple alternatives to an effective channel matrix. Then, the set yielding the largest Frobenius norm (or the largest absolute value of the determinant) of the effective channel provides the solution to the hybrid beamforming problem. The proposed hybrid beamforming approach clearly shows that the performance of hybrid beamforming is dominated by the quality of the coupling coefficients. Considering a fixed-length training sequence, we exploit mmWave channels' sparsity shown in the delay and angular domains to refine the quality of the coupling coefficients as well as to improve the hybrid beamforming performance.

Extremely high data rate demands, and the spectrum scarcity at the microwave bands, make the millimeter wave (mmWave) band a promising solution to satisfy the high data rate demands in wireless networks. The main advantage of moving to the mmWave spectrum is the availability of large bandwidth. Moreover, due to an order of magnitude smaller wavelength of mmWave signals in compared to the conventional bands, many antenna elements can be incorporated in a small size chip to provide high directivity gain both at the transmitter and the receiver sides.Millimeter wave links experience severe vulnerability to the obstacles compared to the conventional sub-6 GHz networks for two main reasons. First, due to the tiny wavelength, mmWave signals can easily be blocked by obstacles in the environment and this causes severe loss. Second, due to the use of directional communications to compensate for the high path-loss (the distance-dependent component of the attenuation), mmWave links are sensitive to blockages that leads to the high probability of beam misalignment and the frequent updating of beamforming vectors. These issues are more challenging in mobile scenarios, in which mobility of the users and obstacles cause frequent re-execution of the beamforming process. Therefore, the tradeoff between the latency of the beamforming process (which latency increases with the number of the re-execution of the beamforming process) and instantaneous user rate is a significant design challenge in mmWave networks. Moreover, to provide adequate coverage and capacity, the density of the base stations in mmWave networks is usually higher than the conventional sub-6 GHz network. This leads to frequent handovers that make maintaining and establishing the mmWave links more challenging. Motivated by the mentioned challenges, this thesis considers the beamforming and handover problems and proposes lightweight joint beamforming and handover methods to guarantee a certain data rate along user trajectory. Specifically, in the first thread of the thesis, inspired by the fundamental properties of the spacial channel response of mmWave links, we propose a beamforming method in mobile mmWave networks. Our analysis reveals that our proposed method is efficient in terms of signaling and computation complexity, power consumption, and throughput in compared to the benchmark.  In the second thread of the thesis, we focus on the handover problem. We formulate the association problem that maximizes the trajectory rate while guarantees a predefined data rate threshold. We then extend our problem to the multi-user dense scenario that the density of the users is higher than the base stations and consider the resource allocation in the association optimization problem. We apply reinforcement learning in order to approximate the solution of the association problem. In general, the main objective of our proposed method is to maximize the sum rates of all the users and minimize the number of the handovers and reduce the probability of the events in which the users' rate becomes less than a predefined threshold. Simulation results confirm that our proposed handover method provides a reliable connection along a trajectory in compared to the benchmarks. / <p>QC 20210407</p>

In this work, an innovative approach for effective modeling of substrate integrated waveguide (SIW) devices is firstly proposed. Next, a novel substrate integrated waveguide power splitter is proposed to feed antenna array elements in series. This feed network inherently provides uniform output power to eight quadrupole antennas. More importantly, it led to a compact configuration since the feed network can be integrated inside the elements without increasing the overall array size. Its design procedure is also presented. Then, a series feed network was used to feed a novel compact omnidirectional antenna array. Targeting the 5G 26 GHz mm-wave frequency band, simulated results showed that the proposed array exhibits a broad impedance bandwidth of 4.15 GHz and a high gain of 13.6 dBi, which agree well with measured results. Its attractive features indicate that the proposed antenna array is well suitable for millimeter-wave wireless communication systems.