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In this thesis low complexity physical layer cooperative communication schemes are investigated to improve the spectral efficiency, the scalability and the coverage range of mobile ad hoc networks (MANETs). Specifically, we investigate cooperative broadcasting and provide an accurate coverage prediction to it, introduce leakage based beam shaping to increase the transmission range of virtual antenna arrays, while the signal in undesired directions is suppressed, and propose simple resource allocation schemes for quantize-and-forward receive cooperation. We provide theoretical analysis and numerical evaluations of these schemes and investigate their performance, respectively the performance of combinations thereof, in two different scenarios: military MANETs and urban traffic hotspots with ultra high user density. In addition to the cooperative communication schemes, we investigate the relation between the applied transmit power and the resulting interference power at unintended users in leakage based precoding, a promising multi-user MIMO precoding approach. Based on these investigations, we propose a target rate precoding as well as a rate optimal precoding, and provide a quasi closed-form solution for both.

Technology. --- Ad hoc networks (Computer networks). --- MANETs (Computer networks) --- Mobile ad hoc networks --- Wireless ad hoc networks --- Computer networks --- Wireless communication systems --- Applied science --- Arts, Useful --- Science, Applied --- Useful arts --- Science --- Industrial arts --- Material culture --- Cooperative communication --- Physical layer --- Virtual antenna array --- High density --- Ad hoc networks (Computer networks)

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Microwave imaging techniques allow for the development of systems that are able to inspect, identify, and characterize in a noninvasive fashion under different scenarios, ranging from biomedical to subsurface diagnostics as well as from surveillance and security applications to nondestructive evaluation. Such great opportunities, though, are actually severely limited by difficulties arising from the solution of the underlying inverse scattering problem. As a result, ongoing research efforts in this area are devoted to developing inversion strategies and experimental apparatus so that they are as reliable and accurate as possible with respect to reconstruction capabilities and resolution performance, respectively. The intent of this Special Issue is to present the experiences of leading scientists in the electromagnetic inverse scattering community, as well as to serve as an assessment tool for people who are new to the area of microwave imaging and electromagnetic inverse scattering problems.

joint sparsity --- magnetic resonance imaging --- near-field measurements --- rank minimization --- compressed sensing --- array diagnosis --- microwave plasma diagnostics --- radar-based breast imaging --- image-based approach --- contraction integral equation for inversion (CIE-I) --- nonlinear optimization --- contrast-source inversion --- electromagnetic inverse scattering problems --- nonlinear problem --- tomography --- RCS estimation --- inverse problems --- discontinuous Galerkin method (DGM) --- microwave imaging profilometry --- electrical-property tomography --- breast imaging --- antenna array --- finite-difference methods --- adjoint inversion methods --- Bayesian compressive sensing (BCS) --- orthogonality sampling method --- inverse scattering --- linear sampling method --- breast cancer --- contrast source inversion (CSI) --- imaging --- electromagnetic inverse scattering --- antenna testing --- stopping criteria --- 3D --- microwave imaging --- Kolmogorov-Smirnov (K-S) test --- inverse obstacles problem --- 5G communication --- inverse source problem

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In recent years, microwave sensing and imaging have acquired an ever-growing importance in several applicative fields, such as non-destructive evaluations in industry and civil engineering, subsurface prospection, security, and biomedical imaging. Indeed, microwave techniques allow, in principle, for information to be obtained directly regarding the physical parameters of the inspected targets (dielectric properties, shape, etc.) by using safe electromagnetic radiations and cost-effective systems. Consequently, a great deal of research activity has recently been devoted to the development of efficient/reliable measurement systems, which are effective data processing algorithms that can be used to solve the underlying electromagnetic inverse scattering problem, and efficient forward solvers to model electromagnetic interactions. Within this framework, this Special Issue aims to provide some insights into recent microwave sensing and imaging systems and techniques.

MW magnetic field --- axial ratio --- polarization --- NV center --- two-dimensional radar imaging --- multiple-input multiple-output (MIMO) radar --- Particle Swarm Optimization (PSO) --- imaging plane calibration algorithm (IPCA) --- microwave tomography --- stroke detection --- DBIM --- linearized inverse scattering --- microwave imaging --- orbital angular momentum --- born approximation --- rytov approximation --- brain stroke --- monitoring --- antenna array --- electromagnetic scattering --- buried objects --- through-wall radar --- inverse scattering --- breast --- multipath --- dynamic range --- software defined radio --- leakage --- frequency-dimension scale --- terahertz --- measurements --- differential imaging --- numerical optimization --- block system inversion --- trade-off analysis --- medical MEMS --- wireless power transfer --- microwave --- thermography --- field illustration --- permittivity --- radar imaging --- target detection --- experimental measurements --- imaging --- wave propagation --- beam summation methods

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In this new book, we present a collection of the advanced developments in reconfigurable antennas and metasurfaces. It begins with a review of reconfigurability technologies, and proceeds to the presentation of a series of reconfigurable antennas, UWB MIMO antennas and reconfigurable arrays. Then, reconfigurable metasurfaces are introduced and the latest advances are presented and discussed.

Technology: general issues --- History of engineering & technology --- Energy industries & utilities --- reconfigurable antenna --- smartphone --- slot antenna --- sub-6G --- band rejected --- envelope correlation co-efficient --- four element MIMO --- polarization diversity --- ultra-wideband multiple input multiple output --- antenna array --- aperiodic array --- full wave analysis --- particle swarm optimization --- reconfigurable antenna arrays --- solid state switches --- RF switching --- magnetic particles --- magnetostatic responsive structures (MRSs) --- wideband reconfigurable antennas --- new feeding techniques --- dual polarization --- multifrequency antennas --- supershape --- reconfigurable antennas --- surface wave array antenna --- metasurface ground plane --- low-profile --- square-ring antennas --- van Atta reflector --- RCS reduction --- structural mode scattering --- metasurfaces --- polarization reconfigurability --- leaky waves --- combo-reconfigurable --- frequency and radiation pattern --- 5G --- millimeter waves --- mobile communication --- flexible antennas --- frequency reconfigurable --- microfluidic antennas --- pattern reconfigurable --- polarization reconfigurable --- wearable antennas --- active FSS --- C-band --- frequency-selective surface (FSS) --- spatial filters --- switchable --- X-band --- smart devices --- antenna boosters --- multiband antennas --- small antennas --- wireless devices --- matching networks --- digitally tunable capacitors --- n/a

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With the rapid evolution of the wireless communications, fifth-generation (5G) communication has received much attention from both academia and industry, with many reported efforts and research outputs and significant improvements in different aspects, such as data rate speed and resolution, mobility, latency, etc. In some countries, the commercialization of 5G communication has already started as well as initial research of beyond technologies such as 6G.MIMO technology with multiple antennas is a promising technology to obtain the requirements of 5G/6G communications. It can significantly enhance the system capacity and resist multipath fading, and has become a hot spot in the field of wireless communications. This technology is a key component and probably the most established to truly reach the promised transfer data rates of future communication systems. In MIMO systems, multiple antennas are deployed at both the transmitter and receiver sides. The greater number of antennas can make the system more resistant to intentional jamming and interference. Massive MIMO with an especially high number of antennas can reduce energy consumption by targeting signals to individual users utilizing beamforming.Apart from sub-6 GHz frequency bands, 5G/6G devices are also expected to cover millimeter-wave (mmWave) and terahertz (THz) spectra. However, moving to higher bands will bring new challenges and will certainly require careful consideration of the antenna design for smart devices. Compact antennas arranged as conformal, planar, and linear arrays can be employed at different portions of base stations and user equipment to form phased arrays with high gain and directional radiation beams. The objective of this Special Issue is to cover all aspects of antenna designs used in existing or future wireless communication systems. The aim is to highlight recent advances, current trends, and possible future developments of 5G/6G antennas.

double-fed slot antenna --- MIMO system --- mobile terminals --- polarization diversity --- UWB technology --- 5G --- future handsets --- modified PIFA --- multi-antenna system --- multi-band operation --- MIMO --- 5G mobile handsets --- dual-band antenna --- microstrip patch antenna --- millimeter-wave --- high gain --- transmitarray (TA) antenna --- metasurface (MS) --- PSO --- side-lobe level (SLL) reduction --- lens antenna --- negative refractive index --- multibeam --- beam scanning --- beyond-5G --- 6G --- interference alignment --- K-User MIMO --- OFDM --- wideband antenna --- MIMO antenna --- four-port wideband antenna --- substrate integrated waveguide (SIW) --- transmission zeros (TZs) --- metallic via --- coupling topology --- antenna array --- antenna measurements --- beam pattern --- beam steering --- equivalent circuit modelling --- transmitarray --- chirality --- dielectric resonator antennas --- metasurfaces --- antipodal Vivaldi antenna (AVA) --- millimeter wave --- compact --- 5G applications --- corrugations --- reconfigurable antennas --- reconfigurable parasitic layers --- antenna optimization --- antenna design --- nonlinear characterization --- behavioral modelling --- x-parameters --- PIN diode --- dielectric resonator antenna --- aperture coupled --- 26 GHz --- small cell --- active metamaterial antenna --- continuous tuning --- resonance blindness --- EM co-simulation --- nonlinear property --- phased array --- massive MIMO --- wideband array --- triangular grid --- n/a