Fine Timing and Frequency Synchronization for MIMO-OFDM: An Extreme Learning Approach

Multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) is a key technology component in the evolution towards cognitive radio (CR) in next-generation communication in which the accuracy of timing and frequency synchronization significantly impacts the overall system performance. In this paper, we propose a novel scheme leveraging extreme learning machine (ELM) to achieve high-precision synchronization. Specifically, exploiting the preamble signals with synchronization offsets, two ELMs are incorporated into a traditional MIMO-OFDM system to estimate both the residual symbol timing offset (RSTO) and the residual carrier frequency offset (RCFO). The simulation results show that the performance of the proposed ELM-based synchronization scheme is superior to the traditional method under both additive white Gaussian noise (AWGN) and frequency selective fading channels. Furthermore, comparing with the existing machine learning based techniques, the proposed method shows outstanding performance without the requirement of perfect channel state information (CSI) and prohibitive computational complexity. Finally, the proposed method is robust in terms of the choice of channel parameters (e.g., number of paths) and also in terms of "generalization ability" from a machine learning standpoint.Comment: 13 pages, 12 figures, has been accepted for publication in IEEE Transactions on Cognitive Communications and Networkin

Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)

Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression

A combined phase contrast imaging and heterodyne interferometer system for multiscale fluctuation measurements on DIII-D

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.Cataloged from PDF version of thesis.Includes bibliographical references.A novel combined diagnostic capable of measuring multiscale density fluctuations that extend from magnetohydrodynamic (MHD) scales to the lower bound of the electron temperature gradient (ETG) mode has been designed, installed, and operated at the DIII-D tokamak. The combined diagnostic was constructed by adding a heterodyne interferometer to the pre-existing phase contrast imaging (PCI) system, both of which measure line-integrated electron-density fluctuations. The port-space footprint is minimized by using a single 10.6 pm CO2 laser and a single beampath. With temporal bandwidths in excess of 1 MHz, the PCI measures high-k (1.5 cm-1 < k +/<kI ; 25 cm-1) fluctuations with sensitivity 3 x 1013 M-2 [square root of] kHz, while the interferometer simultaneously measures low-k (k < 5 cm- 1) fluctuations with sensitivity 3 x 1014 m-2 [square root of]kHz. The intentional mid-k overlap has been empirically verified with sound-wave calibrations and should allow quantitative investigation of the cross-scale coupling predicted to be significant in the reactor-relevant Te ~ Tj regime. The combined PCI-interferometer was operated during an experiment in which the ETG drive a/LT, and the ion temperature gradient (ITG) drive a/LT, were locally modified in an attempt to elicit a multiscale turbulent response. Numerous turbulent branches are observed. In particular, the interferometer measures a low-k electromagnetic mode driven unstable by collisionality, properties consistent with the micro-tearing mode (MTM), and the PCI measures a turbulent mode that exhibits distinct "spectral flattening" when increasing a/LTe relative to a/LTi', hypothesized to be a tell-tale signature of increased cross-scale coupling. Linear-stability analysis and quasi-linear-transport modeling are performed with the trapped gyro-Landau fluid code TGLF, and qualitative agreement with the PCI-measured spectral flattening is obtained. Further, via toroidal correlation with DIII-D's primary interferometer, the measurement of core-localized MHD toroidal mode numbers has been demonstrated. Where comparisons can be made with magnetic probes, the interferometer-measured toroidal mode numbers are typically in good agreement. Unfortunately, the 4 cm major-radial offset between the interferometer beam centers in DIII-D can bias the mode-number measurement, limiting widespread use of this capability until a robust compensation technique is developed.by Evan Michael Davis.Ph. D

Intelligent Biosignal Processing in Wearable and Implantable Sensors

This reprint provides a collection of papers illustrating the state-of-the-art of smart processing of data coming from wearable, implantable or portable sensors. Each paper presents the design, databases used, methodological background, obtained results, and their interpretation for biomedical applications. Revealing examples are brain–machine interfaces for medical rehabilitation, the evaluation of sympathetic nerve activity, a novel automated diagnostic tool based on ECG data to diagnose COVID-19, machine learning-based hypertension risk assessment by means of photoplethysmography and electrocardiography signals, Parkinsonian gait assessment using machine learning tools, thorough analysis of compressive sensing of ECG signals, development of a nanotechnology application for decoding vagus-nerve activity, detection of liver dysfunction using a wearable electronic nose system, prosthetic hand control using surface electromyography, epileptic seizure detection using a CNN, and premature ventricular contraction detection using deep metric learning. Thus, this reprint presents significant clinical applications as well as valuable new research issues, providing current illustrations of this new field of research by addressing the promises, challenges, and hurdles associated with the synergy of biosignal processing and AI through 16 different pertinent studies. Covering a wide range of research and application areas, this book is an excellent resource for researchers, physicians, academics, and PhD or master students working on (bio)signal and image processing, AI, biomaterials, biomechanics, and biotechnology with applications in medicine

NASA Tech Briefs, April 1990

Topics: New Product Ideas; NASA TU Services; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences

Fast Response Scintillator Based Detector for MHD Induced Energetic Ion Losses in ASDEX Upgrade

In fusion plasma devices, fast particles i.e. suprathermal ions generated by heating systems and fusion born a particles must be well confined, until they have transferred their energy to the plasma bulk. Signicant loss of these ions may reduce drastically the heating eficiency and, in addition, may cause damage to plasma facing components in the vacuum vessel, if it is suficiently intense and localized. A detailed knowledge of the underlying physics in particular in the presence of magnetohydrodynamic (MHD) instabilities is of crucial importance, since these instabilities can lead to an enhancement of the outwards fast ion radial drift. The development of a new diagnostic for the study of fast particle-wave interactions in the ASDEX Upgrade tokamak as well as the interpretation of the rst measurements have been the aim of this thesis. The design is based on similar diagnostics that have been operated in the TFTR tokamak and the W7-AS stellerator. The fast ion loss detector acts as a magnetic spectrometer, dispersing fast ions onto a scintillator, with the strike point depending on their gyroradius (energy) and pitch angle (angle between ion velocity and magnetic eld line). The emitted light pattern allows particle identification in the phase space with a high time resolution. The major new development for the diagnostic used on ASDEX Upgrade is the use of a very fast scintillator material that allows sampling rates up to 1 MHz, adequate to study time resolved interactions between MHD modes and fast particles. Fast Ion Losses (FIL) were found in the presence of different kinds of MHD instabilities: time resolved FIL due to Edge Localized Modes (ELMs) have been directly observed. They show a complex behavior of a great variety, depending on the ELM substructure. The influence of ELMs on escaping fast particles is appreciable in the whole lost particle phase space independent of the fast ion source. FIL could be measured in the presence of Toroidal Alfv´en Eigenmodes (TAEs) in ICRH heated discharges. Both species, fast hydrogen and deuterium ions are affected in a similar way by TAEs. A resonant process between the TAE frequency and the precession frequency of the lost ions has been identied by comparisons with HAGIS simulations as the loss mechanism. A new MHD perturbation has been observed for the first time during this thesis by means of its strong influence on the energetic deuterium ion population. The mode is localized deeply in the plasma core and dominates the uxes of lost fast deuterium ions in ICRH heated discharges. Finally, bursts of fast deuterium ions ejected by Neoclassical Tearing Modes have been detected in discharges with different heating systems. In pure NBI heated discharges, these ions have energies approximately equal to the full NBI injection energy and pitch angles corresponding to ions on passing orbits. A detailed study of the FIL signal together with Mirnov coil signals revealed that the losses are due to a diffusive process. According to this, simulations with the ORBIT code have proven that orbit stochasticity is a good candidate for the mechanism that causes the losses of these, in principle well confined, passing ions. These results revealed the high diagnostic potential of this method, opening new ways towards a better understanding of the fast ion physics and therefore will help to predict the behavior of fast ions in the presence of MHD instabilities for ITER

LASER Tech Briefs, September 1993

This edition of LASER Tech briefs contains a feature on photonics. The other topics include: Electronic Components and Circuits. Electronic Systems, Physical Sciences, Materials, Computer Programs, Mechanics, Machinery, Fabrication Technology, Mathematics and Information Sciences, Life Sciences and books and reports

Sensors and Systems for Indoor Positioning

This reprint is a reprint of the articles that appeared in Sensors' (MDPI) Special Issue on “Sensors and Systems for Indoor Positioning". The published original contributions focused on systems and technologies to enable indoor applications