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\"A practical review of state-of-the-art non-contiguous multicarrier technologies that are revolutionizing how data is transmitted, received, and processed This book addresses the advantages and the limitations of modern multicarrier technologies and how to meet the challenges they pose using non-contiguous multicarrier technologies and novel algorithms that enhance spectral efficiency, interference robustness, and reception performance. It explores techniques using non-contiguous subcarriers which allow for flexible spectrum aggregation while achieving high spectral efficiency and flexible transmission and reception at lower OSI layers. These include non-contiguous orthogonal frequency division multiplexing (NC-OFDM), its enhanced version, non-contiguous filter-bank-based multicarrier (NC-FBMC), and generalized multicarrier. Following an overview of current multicarrier technologies for radio communication, the authors examine particular properties of these technologies that allow for more efficient usage within key directions of 5G. They examine the principles of NC-OFDM and discuss efficient transmitter and receiver design. They present the principles of FBMC modulation and discuss key challenges for FBMC communications while comparing performance results with traditional OFDM. They move on from there to a fascinating discussion of GMC modulation within which they clearly demonstrate how that technology encompasses all of the advantages of previously discussed techniques, as well as all imaginable multi- and single-carrier waveforms.; Addresses the problems and limitations of current multicarrier technologies (OFDM) Describes innovative techniques using non-contiguous multicarrier waveforms as well as filter-band based and generalized multicarrier waveforms Provides a thorough review of the practical limitations and solutions for evolving and breakthrough 5G communication technologies Explores the future outlook for non-contiguous multicarrier technologies as regards their greater industrial realization, hardware practicality, and other challenges Advanced Multicarrier Technologies for Future Radio Communication: 5G and Beyondis an indispensable working resource fortelecommunication engineers, researchers and academics, as well as graduate and post-graduate students of telecommunications. At the same time, it provides a fascinating look at the shape of things to come for telecommunication industry executives, telecom operators, regulators, policy makers, and economists. \"-- Provided by publisher.

This paper presents a carrier waves phase shifting method to reduce the dc-link capacitor current for a dual three-phase permanent magnet synchronous motor drive system. Dc-link capacitors absorb the ripple current generated at the input due to the harmonics of the pulse width modulation (PWM). The size, cost, reliability, and lifetime of the dc-link capacitor are negatively affected by this ripple current flowing through it. The proposed method is especially appropriate for common dc-link capacitors for a dual inverter system driving two PMSMs. In this paper, the input current of each inverter is analyzed using Double Fourier Analysis, and the harmonic components of the dc-link capacitor current are determined. The carrier wave phase shifting method is proposed to reduce the magnitude of the harmonics and thus reduce the dc-link capacitor current. Furthermore, the optimum angle between the carrier waves for the maximum reduction in the dc-link capacitor current is analyzed and simulated for different scenarios considering the speed and load torque of the PMSMs. The proposed method is verified through experiments and PMSMs are driven by three-phase voltage source inverters (VSIs) modulated with Space Vector Pulse Width Modulation (SVPWM), which is the most common PWM strategy. The proposed method reduces the dc-link capacitor current by 60%, thereby significantly decreasing the required dc-link capacitance, the volume of the drive system, and its cost.

Harnessing the carrier wave of light as an alternating-current bias may enable electronics at optical clock rates 1 . Lightwave-driven currents have been assumed to be essential for high-harmonic generation in solids 2 – 6 , charge transport in nanostructures 7 , 8 , attosecond-streaking experiments 9 – 16 and atomic-resolution ultrafast microscopy 17 , 18 . However, in conventional semiconductors and dielectrics, the finite effective mass and ultrafast scattering of electrons limit their ballistic excursion and velocity. The Dirac-like, quasi-relativistic band structure of topological insulators 19 – 29 may allow these constraints to be lifted and may thus open a new era of lightwave electronics. To understand the associated, complex motion of electrons, comprehensive experimental access to carrier-wave-driven currents is crucial. Here we report angle-resolved photoemission spectroscopy with subcycle time resolution that enables us to observe directly how the carrier wave of a terahertz light pulse accelerates Dirac fermions in the band structure of the topological surface state of Bi 2 Te 3 . While terahertz streaking of photoemitted electrons traces the electromagnetic field at the surface, the acceleration of Dirac states leads to a strong redistribution of electrons in momentum space. The inertia-free surface currents are protected by spin–momentum locking and reach peak densities as large as two amps per centimetre, with ballistic mean free paths of several hundreds of nanometres, opening up a realistic parameter space for all-coherent lightwave-driven electronic devices. Furthermore, our subcycle-resolution analysis of the band structure may greatly improve our understanding of electron dynamics and strong-field interaction in solids. Time- and angle-resolved photoemission spectroscopy reveals how Dirac fermions in the band structure of the topological surface state of Bi 2 Te 3 are accelerated by the carrier wave of a terahertz-frequency light pulse.

As conventional electronics approaches its limits 1 , nanoscience has urgently sought methods of fast control of electrons at the fundamental quantum level 2 . Lightwave electronics 3 —the foundation of attosecond science 4 —uses the oscillating carrier wave of intense light pulses to control the translational motion of the electron’s charge faster than a single cycle of light 5 – 15 . Despite being particularly promising information carriers, the internal quantum attributes of spin 16 and valley pseudospin 17 – 21 have not been switchable on the subcycle scale. Here we demonstrate lightwave-driven changes of the valley pseudospin and introduce distinct signatures in the optical readout. Photogenerated electron–hole pairs in a monolayer of tungsten diselenide are accelerated and collided by a strong lightwave. The emergence of high-odd-order sidebands and anomalous changes in their polarization direction directly attest to the ultrafast pseudospin dynamics. Quantitative computations combining density functional theory with a non-perturbative quantum many-body approach assign the polarization of the sidebands to a lightwave-induced change of the valley pseudospin and confirm that the process is coherent and adiabatic. Our work opens the door to systematic valleytronic logic at optical clock rates. A strong lightwave in a monolayer of tungsten diselenide drives changes in the valley pseudospin, making valley pseudospin an information carrier that is switchable faster than a single light cycle.

Super rogue waves with an amplitude of up to 5 times the background value are observed in a water-wave tank for the first time. Nonlinear focusing of the local wave amplitude occurs according to the higher-order breather solution of the nonlinear wave equation. The present result shows that rogue waves can also develop from very calm and apparently safe sea states. We expect the result to have a significant impact on studies of extreme ocean waves and to initiate related studies in other disciplines concerned with waves in nonlinear dispersive media, such as optics, plasma physics, and superfluidity.

Scanning probe techniques can leverage atomically precise forces to sculpt matter at surfaces, atom by atom. These forces have been applied quasi-statically to create surface structures 1 – 7 and influence chemical processes 8 , 9 , but exploiting local dynamics 10 – 14 to realize coherent control on the atomic scale remains an intriguing prospect. Chemical reactions 15 – 17 , conformational changes 18 , 19 and desorption 20 have been followed on ultrafast timescales, but directly exerting femtosecond forces on individual atoms to selectively induce molecular motion has yet to be realized. Here we show that the near field of a terahertz wave confined to an atomically sharp tip provides femtosecond atomic-scale forces that selectively induce coherent hindered rotation in the molecular frame of a bistable magnesium phthalocyanine molecule. Combining lightwave-driven scanning tunnelling microscopy 21 – 24 with ultrafast action spectroscopy 10 , 13 , we find that the induced rotation modulates the probability of the molecule switching between its two stable adsorption geometries by up to 39 per cent. Mapping the response of the molecule in space and time confirms that the force acts on the atomic scale and within less than an optical cycle (that is, faster than an oscillation period of the carrier wave of light). We anticipate that our strategy might ultimately enable the coherent manipulation of individual atoms within single molecules or solids so that chemical reactions and ultrafast phase transitions can be manipulated on their intrinsic spatio-temporal scales. The near field of a terahertz wave confined to a scanning probe tip provides femtosecond atomic-scale forces that coherently modulate the switching probability of a molecule between two stable adsorption geometries.

A modified fully nonlinear model of an air–water system in deep water is presented in which the effect of wind in the air is simply represented by a direct link between the air–water interface pressure and the interface slope. The water system is a fully nonlinear Euler model of incompressible and irrotational fluid flow. Our main aim is to establish and compare with a reduced model represented by a forced nonlinear Schrödinger (FNLS) equation that describes wave groups in a weakly nonlinear asymptotic limit. Wave groups are described by the soliton and breather solutions generated by four cases of initial conditions in the relevant parameter regime. Numerical simulations of wave group formation in both models are compared, both with and without wind forcing. The FNLS model gives a good prediction to the modified fully nonlinear model when the wavenumber and wave frequency of the initial carrier waves are close to unity in dimensionless units based on typical carrier wavenumber and wave frequency. Wind forcing induces an exponential growth rate in the maximum amplitude wave. When the wave steepness becomes high in the fully nonlinear model some wave breaking is observed, but the FNLS model continues to predict large waves without breaking and there is then agreement only in the initial stage for the relevant initial conditions and parameter value ranges.

We investigate the effect of constant-vorticity background shear on the properties of wavetrains in deep water. Using the methodology of Fokas (A Unified Approach to Boundary Value Problems, 2008, SIAM), we derive a higher-order nonlinear Schrödinger equation in the presence of shear and surface tension. We show that the presence of shear induces a strong coupling between the carrier wave and the mean-surface displacement. The effects of the background shear on the modulational instability of plane waves is also studied, where it is shown that shear can suppress instability, although not for all carrier wavelengths in the presence of surface tension. These results expand upon the findings of Thomas et al. (Phys. Fluids, vol. 24 (12), 2012, 127102). Using a modification of the generalized Lagrangian mean theory in Andrews & McIntyre (J. Fluid Mech., vol. 89, 1978, pp. 609–646) and approximate formulas for the velocity field in the fluid column, explicit, asymptotic approximations for the Lagrangian and Stokes drift velocities are obtained for plane-wave and Jacobi elliptic function solutions of the nonlinear Schrödinger equation. Numerical approximations to particle trajectories for these solutions are found and the Lagrangian and Stokes drift velocities corresponding to these numerical solutions corroborate the theoretical results. We show that background currents have significant effects on the mean transport properties of waves. In particular, certain combinations of background shear and carrier wave frequency lead to the disappearance of mean-surface mass transport. These results provide a possible explanation for the measurements reported in Smith (J. Phys. Oceanogr., vol. 36, 2006, pp. 1381–1402). Our results also provide further evidence of the viability of the modification of the Stokes drift velocity beyond the standard monochromatic approximation, such as recently proposed in Breivik et al. (J. Phys. Oceanogr., vol. 44, 2014, pp. 2433–2445) in order to obtain a closer match to a range of complex ocean wave spectra.

Communication using terahertz (∼10 12  Hz) electromagnetic waves is critical for developing sixth-generation wireless network infrastructures. Conflictions between stable radiation and frequency modulation of terahertz sources impede the superposing of transmitting signals on carrier waves. The Josephson junctions included in a cuprate superconductor radiate terahertz waves with frequencies proportional to the bias voltages. Thus, the modulation of the bias voltage leads to the modulation of the Josephson plasma emission (JPE) frequency. This study aims to demonstrate the generation of frequency-modulated (FM) terahertz continuous waves from Josephson junctions. A FM bandwidth of up to 40 GHz was achieved when 3 GHz sinusoidal waves were superimposed on 840–890 GHz carrier waves radiated by a JPE. The results verify that the instantaneous JPE frequency follows the gigahertz-modulated bias voltage. The wide-band FM terahertz generation by a monolithic device shows a sharp contrast to the mode-lock frequency comb constructed using highly sophisticated optics on a bench. A further increase of the modulation amplitude facilitates up- or downconversion of frequencies over more than one octave. The obtained FM bandwidth exhibited an improvement of two orders of magnitude in the demodulation signal-to-noise ratio compared with the amplitude-modulated waves. The demonstrated FM JPE stimulates further research on terahertz communication technology and metrology using superconducting devices. Frequency-modulated terahertz continuous waves are generated from Josephson junctions included in a cuprate superconductor. When 3 GHz sinusoidal waves were superimposed on 840–890 GHz carrier waves, the modulation bandwidth reached 40 GHz when a Josephson plasma emission was utilized.

This paper examines experimentally the dispersion and stability of weakly nonlinear waves on opposing linearly vertically sheared current profiles (with constant vorticity). Measurements are compared against predictions from the unidirectional (1D+1) constant vorticity nonlinear Schrödinger equation (the vor-NLSE) derived by Thomas et al. (Phys. Fluids, vol. 24, no. 12, 2012, 127102). The shear rate is negative in opposing currents when the magnitude of the current in the laboratory reference frame is negative (i.e. opposing the direction of wave propagation) and reduces with depth, as is most commonly encountered in nature. Compared to a uniform current with the same surface velocity, negative shear has the effect of increasing wavelength and enhancing stability. In experiments with a regular low-steepness wave, the dispersion relationship between wavelength and frequency is examined on five opposing current profiles with shear rates from 0 to −0.87 s−1 . For all current profiles, the linear constant vorticity dispersion relation predicts the wavenumber to within the 95% confidence bounds associated with estimates of shear rate and surface current velocity. The effect of shear on modulational instability was determined by the spectral evolution of a carrier wave seeded with spectral sidebands on opposing current profiles with shear rates between 0 and −0.48 s−1 . Numerical solutions of the vor-NLSE are consistently found to predict sideband growth to within two standard deviations across repeated experiments, performing considerably better than its uniform-current NLSE counterpart. Similarly, the amplification of experimental wave envelopes is predicted well by numerical solutions of the vor-NLSE, and significantly over-predicted by the uniform-current NLSE.