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Array Beamforming Enabled Wireless Communications
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Book Synopsis Array Beamforming Enabled Wireless Communications by : Zhenyu Xiao
Download or read book Array Beamforming Enabled Wireless Communications written by Zhenyu Xiao and published by CRC Press. This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This book investigates the most advanced theories and methodologies of array beamforming, with a focus on antenna array enabled wireless communication technology. Combining with current development needs and trends of wireless communication technology around the world, the authors explore the potentials and challenges of large-scale antenna array beamforming technology in next-generation mobile communication and some important emerging application scenarios. The book first introduces the basic structure of antenna array hierarchical codebook and channel estimation with high dimensionality, with which the time cost of searching the channel information can be effectively reduced. It then explicates high-efficiency beamforming transmission methods for point-to-point transmission, full-duplex point-to-point transmission, and point-to-multipoint transmission where array beamforming enabled non-orthogonal multiple access (NOMA) technologies for typical two-user system and general multi-user system are emphasized. The title also discusses array beamforming enabled unmanned aerial vehicle (UAV) communications and array beamforming enabled space/air/ground communications, with the uniqueness and relative solutions for single UAV system and multi-UAV network analyzed. This will be a vital reference for researchers, students and professionals interested in wireless communications, array beamforming, and millimeter-wave communications"--
Book Synopsis Array Beamforming Enabled Wireless Communications by : Zhenyu Xiao
Download or read book Array Beamforming Enabled Wireless Communications written by Zhenyu Xiao and published by CRC Press. This book was released on 2023-04-25 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book investigates the most advanced theories and methodologies of array beamforming, with a focus on antenna array enabled wireless communication technology. Combining with the current development needs and trends of wireless communication technology around the world, the authors explore the potentials and challenges of large-scale antenna array beamforming technology in next-generation mobile communication and some important emerging application scenarios. The book first introduces the basic structure of antenna array hierarchical codebook and channel estimation with high dimensionality, with which the time cost of searching the channel information can be effectively reduced. It then explicates high-efficiency beamforming transmission methods for point-to-point transmission, full-duplex point-to-point transmission, and point-to-multipoint transmission where array beamforming enabled non-orthogonal multiple access (NOMA) technologies for typical two-user systems and general multi-user systems are emphasized. The book also discusses array beamforming enabled unmanned aerial vehicle (UAV) communications and array beamforming enabled space/air/ground communications, with the uniqueness and relative solutions for single UAV systems and multi-UAV networks being analyzed. This will be a vital reference for researchers, students, and professionals interested in wireless communications, array beamforming, and millimeter-wave communications.
Book Synopsis Advanced Antenna Array Engineering for 6G and Beyond Wireless Communications by : Yingjie Jay Guo
Download or read book Advanced Antenna Array Engineering for 6G and Beyond Wireless Communications written by Yingjie Jay Guo and published by John Wiley & Sons. This book was released on 2021-10-26 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advanced Antenna Array Engineering for 6G and Beyond Wireless Communications Reviews advances in the design and deployment of antenna arrays for future generations of wireless communication systems, offering new solutions for the telecommunications industry Advanced Antenna Array Engineering for 6G and Beyond Wireless Communications addresses the challenges in designing and deploying antennas and antenna arrays which deliver 6G and beyond performance with high energy efficiency and possess the capability of being immune to interference caused by different systems mounted on the same platforms. This timely and authoritative volume presents innovative solutions for developing integrated communications networks of high-gain, individually-scannable, multi-beam antennas that are reconfigurable and conformable to all platforms, thus enabling the evolving integrated land, air and space communications networks. The text begins with an up-to-date discussion of the engineering issues facing future wireless communications systems, followed by a detailed discussion of different beamforming networks for multi-beam antennas. Subsequent chapters address problems of 4G/5G antenna collocation, discuss differentially-fed antenna arrays, explore conformal transmit arrays for airborne platforms, and present latest results on fixed frequency beam scanning leaky wave antennas as well as various analogue beam synthesizing strategies. Based primarily on the authors’ extensive work in the field, including original research never before published, this important new volume: Reviews multi-beam feed networks, array decoupling and de-scattering methods Provides a systematic study on differentially fed antenna arrays that are resistant to interference caused by future multifunctional/multi-generation systems Features previously unpublished material on conformal transmit arrays based on Huygen’s metasufaces and reconfigurable leaky wave antennas Includes novel algorithms for synthesizing and optimizing thinned massive arrays, conformal arrays, frequency invariant arrays, and other future arrays Advanced Antenna Array Engineering for 6G and Beyond Wireless Communications is an invaluable resource for antenna engineers and researchers, as well as graduate and senior undergraduate students in the field.
Book Synopsis Simplified Robust Adaptive Detection and Beamforming for Wireless Communications by : Ayman Elnashar
Download or read book Simplified Robust Adaptive Detection and Beamforming for Wireless Communications written by Ayman Elnashar and published by John Wiley & Sons. This book was released on 2018-06-11 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents an alternative and simplified approaches for the robust adaptive detection and beamforming in wireless communications. It adopts several systems models including DS/CDMA, OFDM/MIMO with antenna array, and general antenna arrays beamforming model. It presents and analyzes recently developed detection and beamforming algorithms with an emphasis on robustness. In addition, simplified and efficient robust adaptive detection and beamforming techniques are presented and compared with exiting techniques. Practical examples based on the above systems models are provided to exemplify the developed detectors and beamforming algorithms. Moreover, the developed techniques are implemented using MATLAB—and the relevant MATLAB scripts are provided to help the readers to develop and analyze the presented algorithms. em style="mso-bidi-font-style: normal;"Simplified Robust Adaptive Detection and Beamforming for Wireless Communications starts by introducing readers to adaptive signal processing and robust adaptive detection. It then goes on to cover Wireless Systems Models. The robust adaptive detectors and beamformers are implemented using the well-known algorithms including LMS, RLS, IQRD-RLS, RSD, BSCMA, CG, and SD. The robust detection and beamforming are derived based on the existing detectors/beamformers including MOE, PLIC, LCCMA, LCMV, MVDR, BSCMA, and MBER. The adopted cost functions include MSE, BER, CM, MV, and SINR/SNR.
Book Synopsis Fundamentals of Wireless Communication by : David Tse
Download or read book Fundamentals of Wireless Communication written by David Tse and published by Cambridge University Press. This book was released on 2005-05-26 with total page 598 pages. Available in PDF, EPUB and Kindle. Book excerpt: This textbook takes a unified view of the fundamentals of wireless communication and explains cutting-edge concepts in a simple and intuitive way. An abundant supply of exercises make it ideal for graduate courses in electrical and computer engineering and it will also be of great interest to practising engineers.
Book Synopsis Multifunctional Antennas and Arrays for Wireless Communication Systems by : Satish K. Sharma
Download or read book Multifunctional Antennas and Arrays for Wireless Communication Systems written by Satish K. Sharma and published by John Wiley & Sons. This book was released on 2021-04-13 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt: MULTIFUNCTIONAL ANTENNAS AND ARRAYS FOR WIRELESS COMMUNICATION SYSTEMS Offers an up-to-date discussion of multifunctional antennas and arrays for wireless communication systems Multifunctional Antennas and Arrays for Wireless Communication Systems is a comprehensive reference on state-of-the-art reconfigurable antennas and 4G/5G communication antennas. The book gives a unique perspective while giving a comprehensive overview of the following topics: Frequency reconfigurable antennas Pattern reconfigurable antennas Polarization reconfigurable antennas Reconfigurable antennas using Liquid Metal, Piezoelectric, and RF MEMS MIMO and 4G/5G wireless communication antennas Metamaterials and metasurfaces in reconfigurable antennas Multifunctional antennas for user equipments (UEs) Defense related antennas and applications Flat panel phased array antennas The book is a valuable resource for the practicing engineer as well as for those within the research field. As wireless communications continuously evolves, more and more functionally will be required, and thus multifunctional antennas and RF systems will be necessary. These multifunctional antennas will require a degree of reconfigurability, and this book discusses various methods which enable this. The main topics of frequency, pattern, and polarization reconfigurability is first discussed. Methods utilizing unique materials and devices, both real and artificial are discussed. The book also delves into 4G/5G antennas as it relates to MIMO, and millimeter-wave phased arrays. Finally, there is a section on defense related multifunctional RF antenna systems.
Download or read book Wideband Beamforming written by Wei Liu and published by John Wiley & Sons. This book was released on 2010-03-18 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides an excellent reference for all professionals working in the area of array signal processing and its applications in wireless communications. Wideband beamforming has advanced with the increasing bandwidth in wireless communications and the development of ultra wideband (UWB) technology. In this book, the authors address the fundamentals and most recent developments in the field of wideband beamforming. The book provides a thorough coverage of the subject including major sub-areas such as sub-band adaptive beamforming, frequency invariant beamforming, blind wideband beamforming, beamforming without temporal processing, and beamforming for multi-path signals. Key Features: Unique book focusing on wideband beamforming Discusses a hot topic coinciding with the increasing bandwidth in wireless communications and the development of UWB technology Addresses the general concept of beamforming including fixed beamformers and adaptive beamformers Covers advanced topics including sub-band adaptive beamforming, frequency invariant beamforming, blind wideband beamforming, beamforming without temporal processing, and beamforming for multi-path signals Includes various design examples and corresponding complexity analyses This book provides a reference for engineers and researchers in wireless communications and signal processing fields. Postgraduate students studying signal processing will also find this book of interest.
Book Synopsis Wireless Communication Using Dual Antenna Arrays by : Da-shan Shiu
Download or read book Wireless Communication Using Dual Antenna Arrays written by Da-shan Shiu and published by Springer Science & Business Media. This book was released on 2006-04-18 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: At present, the expansion of tetherless communications is a technological trend surpassed perhaps only by the explosive growth of the Internet. Wireless systems are being deployed today mainly for telephony, satisfying the ind- trialized nations’ appetite for talk-on-the-go, and providing much-needed communications infrastructure in developing countries. The desire for wi- less access to the Internet is starting to add fuel to the growth of tetherless communications. Indeed, the synergy of wireless and Internet technologies will lead to a host of exciting new applications, some of which are not yet envisioned. Future-generation wireless systems will achieve capacities much higher than the systems of today by incorporating myriad improvements. These in- vations include transmission in higher-frequency bands, “smart antennas”, multi-user detection, new forward error-correction techniques, and advanced network resource-allocation techniques. The term “smart antenna” usually refers to the deployment of multiple antennas at the base-station site, coupled with special processing of the m- tiple received signals. Smart antennas can adaptively reject co-channel int- ference and mitigate multipath fading, and have been identified by many as a promising means to extend base-station coverage, increase system capacity and enhance quality of service.
Book Synopsis Digital Beamforming in Wireless Communications by : John Litva
Download or read book Digital Beamforming in Wireless Communications written by John Litva and published by Artech House Mobile Communicat. This book was released on 1996 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt: Explosive growth of wireless communications is demanding increased system capacity for mobile communications satellites - and the expert authors of this first-of-a-kind book explore a promising, cost-effective solution: digital beamforming (DBF) technology.
Book Synopsis New Directions in Wireless Communications Systems by : Athanasios G. Kanatas
Download or read book New Directions in Wireless Communications Systems written by Athanasios G. Kanatas and published by CRC Press. This book was released on 2017-10-16 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt: Beyond 2020, wireless communication systems will have to support more than 1,000 times the traffic volume of today's systems. This extremely high traffic load is a major issue faced by 5G designers and researchers. This challenge will be met by a combination of parallel techniques that will use more spectrum more flexibly, realize higher spectral efficiency, and densify cells. Novel techniques and paradigms must be developed to meet these goals. The book addresses diverse key-point issues of next-generation wireless communications systems and identifies promising solutions. The book's core is concentrated to techniques and methods belonging to what is generally called radio access network.
Download or read book Massive MIMO written by Hien Quoc Ngo and published by Linköping University Electronic Press. This book was released on 2015-01-16 with total page 45 pages. Available in PDF, EPUB and Kindle. Book excerpt: The last ten years have seen a massive growth in the number of connected wireless devices. Billions of devices are connected and managed by wireless networks. At the same time, each device needs a high throughput to support applications such as voice, real-time video, movies, and games. Demands for wireless throughput and the number of wireless devices will always increase. In addition, there is a growing concern about energy consumption of wireless communication systems. Thus, future wireless systems have to satisfy three main requirements: i) having a high throughput; ii) simultaneously serving many users; and iii) having less energy consumption. Massive multiple-input multiple-output (MIMO) technology, where a base station (BS) equipped with very large number of antennas (collocated or distributed) serves many users in the same time-frequency resource, can meet the above requirements, and hence, it is a promising candidate technology for next generations of wireless systems. With massive antenna arrays at the BS, for most propagation environments, the channels become favorable, i.e., the channel vectors between the users and the BS are (nearly) pairwisely orthogonal, and hence, linear processing is nearly optimal. A huge throughput and energy efficiency can be achieved due to the multiplexing gain and the array gain. In particular, with a simple power control scheme, Massive MIMO can offer uniformly good service for all users. In this dissertation, we focus on the performance of Massive MIMO. The dissertation consists of two main parts: fundamentals and system designs of Massive MIMO. In the first part, we focus on fundamental limits of the system performance under practical constraints such as low complexity processing, limited length of each coherence interval, intercell interference, and finite-dimensional channels. We first study the potential for power savings of the Massive MIMO uplink with maximum-ratio combining (MRC), zero-forcing, and minimum mean-square error receivers, under perfect and imperfect channels. The energy and spectral efficiency tradeoff is investigated. Secondly, we consider a physical channel model where the angular domain is divided into a finite number of distinct directions. A lower bound on the capacity is derived, and the effect of pilot contamination in this finite-dimensional channel model is analyzed. Finally, some aspects of favorable propagation in Massive MIMO under Rayleigh fading and line-of-sight (LoS) channels are investigated. We show that both Rayleigh fading and LoS environments offer favorable propagation. In the second part, based on the fundamental analysis in the first part, we propose some system designs for Massive MIMO. The acquisition of channel state information (CSI) is very importantin Massive MIMO. Typically, the channels are estimated at the BS through uplink training. Owing to the limited length of the coherence interval, the system performance is limited by pilot contamination. To reduce the pilot contamination effect, we propose an eigenvalue-decomposition-based scheme to estimate the channel directly from the received data. The proposed scheme results in better performance compared with the conventional training schemes due to the reduced pilot contamination. Another important issue of CSI acquisition in Massive MIMO is how to acquire CSI at the users. To address this issue, we propose two channel estimation schemes at the users: i) a downlink "beamforming training" scheme, and ii) a method for blind estimation of the effective downlink channel gains. In both schemes, the channel estimation overhead is independent of the number of BS antennas. We also derive the optimal pilot and data powers as well as the training duration allocation to maximize the sum spectral efficiency of the Massive MIMO uplink with MRC receivers, for a given total energy budget spent in a coherence interval. Finally, applications of Massive MIMO in relay channels are proposed and analyzed. Specifically, we consider multipair relaying systems where many sources simultaneously communicate with many destinations in the same time-frequency resource with the help of a massive MIMO relay. A massive MIMO relay is equipped with many collocated or distributed antennas. We consider different duplexing modes (full-duplex and half-duplex) and different relaying protocols (amplify-and-forward, decode-and-forward, two-way relaying, and one-way relaying) at the relay. The potential benefits of massive MIMO technology in these relaying systems are explored in terms of spectral efficiency and power efficiency.
Book Synopsis Handbook of Antennas in Wireless Communications by : Lal Chand Godara
Download or read book Handbook of Antennas in Wireless Communications written by Lal Chand Godara and published by CRC Press. This book was released on 2001-08-16 with total page 936 pages. Available in PDF, EPUB and Kindle. Book excerpt: The move toward worldwide wireless communications continues at a remarkable pace, and the antenna element of the technology is crucial to its success. With contributions from more than 30 international experts, the Handbook of Antennas in Wireless Communications brings together all of the latest research and results to provide engineering professionals and students with a one-stop reference on the theory, technologies, and applications for indoor, hand-held, mobile, and satellite systems. Beginning with an introduction to wireless communications systems, it offers an in-depth treatment of propagation prediction and fading channels. It then explores antenna technology with discussion of antenna design methods and the various antennas in current use or development for base stations, hand held devices, satellite communications, and shaping beams. The discussions then move to smart antennas and phased array technology, including details on array theory and beamforming techniques. Space diversity, direction-of-arrival estimation, source tracking, and blind source separation methods are addressed, as are the implementation of smart antennas and the results of field trials of systems using smart antennas implemented. Finally, the hot media topic of the safety of mobile phones receives due attention, including details of how the human body interacts with the electromagnetic fields of these devices. Its logical development and extensive range of diagrams, figures, and photographs make this handbook easy to follow and provide a clear understanding of design techniques and the performance of finished products. Its unique, comprehensive coverage written by top experts in their fields promises to make the Handbook of Antennas in Wireless Communications the standard reference for the field.
Book Synopsis Introduction to Smart Antennas by : Constantine A. Balanis
Download or read book Introduction to Smart Antennas written by Constantine A. Balanis and published by Morgan & Claypool Publishers. This book was released on 2007 with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt: As the growing demand for mobile communications is constantly increasing, the need for better coverage, improved capacity, and higher transmission quality rises. Thus, a more efficient use of the radio spectrum is required. Smart antenna systems are capable of efficiently utilizing the radio spectrum and is a promise for an effective solution to the present wireless systems' problems while achieving reliable and robust high-speed high-data-rate transmission. The purpose of this book is to provide the reader a broad view of the system aspects of smart antennas. In fact, smart antenna systems comprise several critical areas such as individual antenna array design, signal processing algorithms, space-time processing, wireless channel modeling and coding, and network performance. In this book we include an overview of smart antenna concepts, introduce some of the areas that impact smart antennas, and examine the influence of interaction and integration of these areas to Mobile Ad-Hoc Networks. In addition, the general principles and major benefits of using space-time processing are introduced, especially employing multiple-input multiple-output (MIMO) techniques.
Book Synopsis 6G Wireless Communications and Mobile Networking by : Xianzhong Xie
Download or read book 6G Wireless Communications and Mobile Networking written by Xianzhong Xie and published by Bentham Science Publishers. This book was released on 2021-05-31 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: 6G Wireless Communications and Mobile Networking introduces the key technologies behind 6G wireless communication and mobile networking to the reader. The book starts with a general vision of 6G technology, which includes the motivation that drives 6G research, the international organizations working on 6G standardization and recent progress in 6G research. Separate chapters on millimeter-wave and terahertz-wave technologies in 6G, the development of latest 6G antenna technology as well as related wireless communication applications are included in the contents. The book also provides details about the 6G network layer, such as self-organizing network driven by network slicing, software-defined networking and network function virtualization. Finally, it covers some popular research topics, including the challenges and solutions to massive 6G IoT networks, 6G cloud/edge computing and big data systems that may appear in the foreseeable future. Key Features: - Provides a complete introduction to 6G vision and technology - Consists of both basic theories and frontier technologies - Separate chapters on key topics such as 6G physical layers, millimeter wave and terahertz technology and advanced antenna arrays - Covers future trends and applications such as intelligent management systems, 6G IoT networks, cloud/edge computing and big data applications This focused reference will significantly enhance the knowledge of engineering students and apprentices involved in the field of telecommunications. Readers interested in cutting-edge wireless networking technologies will also benefit from the information provided.
Book Synopsis Millimetre Wave Antennas for Gigabit Wireless Communications by : Kao-Cheng Huang
Download or read book Millimetre Wave Antennas for Gigabit Wireless Communications written by Kao-Cheng Huang and published by John Wiley & Sons. This book was released on 2008-10-13 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: Complete and comprehensive application-focused reference on millimetre wave antennas Millimetre Wave Antennas for Gigabit Wireless Communications covers a vast wealth of material with a strong focus on the current design and analysis principles of millimetre wave antennas for wireless devices. It provides practising engineers with the design rules and considerations required in designing antennas for the terminal. The authors include coverage of new configurations with advanced angular and frequency filtering characteristics, new design and analysis techniques, and methods for filter miniaturization. The book reviews up-to-date research results and utilizes numerous design examples to emphasize computer analysis and synthesis whilst also discussing the applications of commercially available software. Key Features: Advanced and up-to-date treatment of one of the fastest growing fields of wireless communications Covers topics such as Gigabit wireless communications and its required antennas, passive and active antenna design and analysis techniques, multibeam antennas and MIMO, IEEE 802.15.3c, WiMedia®, and advanced materials and technologies Offers a practical guide to integrated antennas for specific configurations requirements Addresses a number of complex, real-world problems that system and antenna engineers are going to face in millimetre-wave communications industry and provides solutions Contains detailed design examples, drawings and predicted performance This book is an invaluable tool for antenna professionals (engineers, designers, and developers), microwave professionals, wireless communication system professionals, and industries with microwave and millimetre wave research projects. Advanced students and researchers working in the field of millimetre wave engineering will also find this book very useful.
Book Synopsis Spectrum Sharing by : Constantinos B. Papadias
Download or read book Spectrum Sharing written by Constantinos B. Papadias and published by John Wiley & Sons. This book was released on 2020-04-06 with total page 484 pages. Available in PDF, EPUB and Kindle. Book excerpt: Combines the latest trends in spectrum sharing, both from a research and a standards/regulation/experimental standpoint Written by noted professionals from academia, industry, and research labs, this unique book provides a comprehensive treatment of the principles and architectures for spectrum sharing in order to help with the existing and future spectrum crunch issues. It presents readers with the most current standardization trends, including CEPT / CEE, eLSA, CBRS, MulteFire, LTE-Unlicensed (LTE-U), LTE WLAN integration with Internet Protocol security tunnel (LWIP), and LTE/Wi-Fi aggregation (LWA), and offers substantial trials and experimental results, as well as system-level performance evaluation results. The book also includes a chapter focusing on spectrum policy reinforcement and another on the economics of spectrum sharing. Beginning with the historic form of cognitive radio, Spectrum Sharing: The Next Frontier in Wireless Networks continues with current standardized forms of spectrum sharing, and reviews all of the technical ingredients that may arise in spectrum sharing approaches. It also looks at policy and implementation aspects and ponders the future of the field. White spaces and data base-assisted spectrum sharing are discussed, as well as the licensed shared access approach and cooperative communication techniques. The book also covers reciprocity-based beam forming techniques for spectrum sharing in MIMO networks; resource allocation for shared spectrum networks; large scale wireless spectrum monitoring; and much more. Contains all the latest standardization trends, such as CEPT / ECC, eLSA, CBRS, MulteFire, LTE-Unlicensed (LTE-U), LTE WLAN integration with Internet Protocol security tunnel (LWIP) and LTE/Wi-Fi aggregation (LWA) Presents a number of emerging technologies for future spectrum sharing (collaborative sensing, cooperative communication, reciprocity-based beamforming, etc.), as well as novel spectrum sharing paradigms (e.g. in full duplex and radar systems) Includes substantial trials and experimental results, as well as system-level performance evaluation results Contains a dedicated chapter on spectrum policy reinforcement and one on the economics of spectrum sharing Edited by experts in the field, and featuring contributions by respected professionals in the field world wide Spectrum Sharing: The Next Frontier in Wireless Networks is highly recommended for graduate students and researchers working in the areas of wireless communications and signal processing engineering. It would also benefit radio communications engineers and practitioners.
Book Synopsis Blind Massive MIMO Base Stations by : Marcus Karlsson
Download or read book Blind Massive MIMO Base Stations written by Marcus Karlsson and published by Linköping University Electronic Press. This book was released on 2018-08-15 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt: Massive MIMO (Multiple-Input--Multiple-Output) is a cellular-network technology in which the base station is equipped with a large number of antennas and aims to serve several different users simultaneously, on the same frequency resource through spatial multiplexing. This is made possible by employing efficient beamforming, based on channel estimates acquired from uplink reference signals, where the base station can transmit the signals in such a way that they add up constructively at the users and destructively elsewhere. The multiplexing together with the array gain from the beamforming can increase the spectral efficiency over contemporary systems. One challenge of practical importance is how to transmit data in the downlink when no channel state information is available. When a user initially joins the network, prior to transmitting uplink reference signals that enable beamforming, it needs system information---instructions on how to properly function within the network. It is transmission of system information that is the main focus of this thesis. In particular, the thesis analyzes how the reliability of the transmission of system information depends on the available amount of diversity. It is shown how downlink reference signals, space-time block codes, and power allocation can be used to improve the reliability of this transmission. In order to estimate the uplink and downlink channels from uplink reference signals, which is imperative to ensure scalability in the number of base station antennas, massive MIMO relies on channel reciprocity. This thesis shows that the principles of channel reciprocity can also be exploited by a jammer, a malicious transmitter, aiming to disrupt legitimate communication between two single-antenna devices. A heuristic scheme is proposed in which the jammer estimates the channel to a target device blindly, without any knowledge of the transmitted legitimate signals, and subsequently beamforms noise towards the target. Under the same power constraint, the proposed jammer can disrupt the legitimate link more effectively than a conventional omnidirectional jammer in many cases. Massiv MIMO (eng: Multiple-Input--Multiple-Output) är en teknologi inom cellulär kommunikation som förutspås ha en betydande roll i framtida kommunikationssystem på grund av de många fördelar som denna teknologi medför. Massiv MIMO innebär att basstationen har ett stort antal antenner där varje antenn kan styras individuellt. De många antennerna gör att basstationen kan rikta de elektromagnetiska signalerna på ett sådant sätt att de förstärks på positioner där användarna befinner sig men släcks ut i övrigt. Detta i sin tur innebär att flera användare kan betjänas samtidigt, på samma frekvensband utan att de stör varandra. Detta medför att massiv MIMO kan erbjuda en högre datatakt än nutida cellulära kommunikationssystem. För att kunna rikta signalerna på ett effektivt sätt måste basstationen känna till kanalen, eller utbredningsmiljön, mellan sig själv och de användare som betjänas. När en användare precis kommer in i systemet vet basstationen inte var användaren befinner sig, men måste likväl tillgodose användaren med information om hur systemet fungerar. Nu måste alltså basstationen kommunicera med användaren, utan möjligheten att kunna rikta signalen på ett effektivt sätt. Det är detta problem som vi i huvudsak studerar i denna avhandling: hur man kan utnyttja de många antennerna på basstationen för att skicka information till användarna utan någon kanalkännedom. Vi studerar även hur en gruppantenn med många antenner, baserad på samma teknologi som massiv MIMO, kan användas som en störsändare. Störsändarens mål är att hindra kommunikationen mellan två enheter på ett effektivt sätt. En störsändare med ett stort antal antenner kan, utan någon kännedom av vad de två enheterna skickar, i många fall prestera bättre än en konventionell störsändare på grund av att störsignalen kan riktas mot en specifik enhet.
