DOCSLIB.ORG

Advanced Communications Project

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Advanced Communications Project Advanced Communications Project Technology Reference Document ELO DEV PM & EN H T C C R E A N E T S E Prepared for E R R The United States Coast Guard Research & Development Center U 1082 Shennecossett Rd. N D I R T A Groton, CT 06340-6096 E U D G S T T A S T E S C O A By VisiCom Laboratories Inc. 1198 Gulf Breeze Parkway Gulf Breeze, FL 32561 September 1993 EXECUTIVE SUMMARY This document is an updated version of the 1985 Technology Reference Document prepared for the U.S. Coast Guard Research and Development Center. It has fully incorporated the contents of the 1985 document. No attempt was made to perform any editorial changes on the 1985 material, with the sole exception of correcting any information which is no longer accurate or applicable due to the evolution of technology. The major changes to the document have been in the area of reorganization / style, the addition of new telecommunications technology information, and the inclusion of information regarding the U.S. navy Satellite Communications System. To provide an all encompassing technology document was beyond the scope of this particular effort. Consequently, the new technology introduced with this updated document has focused on selected topics which were considered by the authors to be of prime importance to U.S. Coast Guard personnel. The following technologies were selected: • Electromagnetic Frequency • Transmission Hardware Spectrum Technology • Over the Horizon Radio • Analog Modulation Communications • Digital Modulation • Radio Frequency Modulation • Information Coding/Processing • Communications Channel Multiplex/ Access • Communications Networks • Integrated Services Digital Network • Cellular Mobile Transmission • Satellite Communications • Computer Architecture Concepts • Security • Communications and Network • Fleet Satellite Communications Services • U.S. Navy Users and Network • Interoperability Architecture Architecture The new topics added to this edition of the Technology Reference Document were arbitrarily selected based on industry and DoD trends and technology feasibility. Since many areas of telecommunications technology are undergoing rapid evolution, comments are anticipated and are actively solicited for eventual inclusion into future editions of this document. 1 ELECTROMAGNETIC FREQUENCY SPECTRUM 1 ELECTROMAGNETIC FREQUENCY SPECTRUM 1.1 Frequency Spectrum Definition 1.2 Extremely Low Frequency (ELF) 1.3 Very Low Frequency (VLF) 1.4 Low Frequency (LF) 1.5 Medium Frequency (MF) 1.6 High Frequency (HF) 1.7 Very High Frequency (VHF) 1.8 Ultra-high Frequency (UHF) 1.9 Super high Frequency (SHF) 1.10 Light Amplification by Stimulated Emission of Radiation (LASER) 1-1 1.1 Frequency Spectrum Definition The continuum of the electromagnetic frequency spectrum useful for communications range from the Extremely Low Frequency (ELF) (designated 30-300 hertz) to the Extremely High Frequency (EHF) (designated 30-300 GHz) millimeter waves. Table 1-1 below specifies the designated nomenclature for those frequencies used in communications. Table 1-1. Electromagnetic Spectrum Nomenclature FREQUENCY RANGE DESIGNATION CLASSIFICATION 30 – 300 Hz ELF Extremely Low Frequency 3 – 30 kHz VLF Very Low Frequency 30 – 300 kHz LF Low Frequency .3 – 3 MHz MF Medium Frequency .3 – 30 MHZ HF High Frequency 30 – 300 MHz VHF Very High Frequency . 3 – 3 GHz UHF Ultra-high Frequency 3 – 30 GHz SHF Super High Frequency 30 – 300 GHz EHF Extremely High Frequency Letter designations are also used for Radio Frequency (RF). Table 1-2 lists the military letter designations for RF frequencies. Table 1-2. Military Radio Frequency Bands BAND DESIGNATION FREQUENCY RANGE A 0 – 250 MHz B 250 – 500 MHz C 500 – 1000 MHz D 1 – 2 GHz E 2 – 3 GHz F 3 – 4 GHz G 4 – 6 GHz H 6 – 8 GHz I 8 – 10 GHz J 10 – 20 GHz K 20 – 40 GHz L 40 – 60 GHz M 60 – 100 GHz 1-2 Electromagnetic waves are propagated from a transmitting antenna to a receiving antenna in a number of different ways besides through a direct path through the atmosphere (line-of-sight/space wave). They may also be propagated along the earth's surface (ground wave), or through refraction or reflection or scattering from natural atmospheric reflectors. Significant reflecting and scattering modes of electromagnetic propagation include ionospheric and tropospheric scattering. Each of these types of electromagnetic propagation is further discussed in Section 3 (Over-the- Horizon Radio Communications). Figure 1-1 illustrates the various types of electromagnetic propagation. IONOSPHERE Ionospheric Refraction Ionospheric Scatter STRATOSPHERE Ionospheric Refraction Tropospheric Scatter TROPOSPHERE Line-of-Sight/Direct Wave EARTH Earth Wave 3683JC7/93 Figure 1-1. Electromagnetic Propagation 1.2 Extremely Low Frequency (ELF) ELF is the communications band extending from 30 Hz to 300 Hz. Transmission is conducted over areas of low conductivity bedrock. The signal is broadcast by orthogonal antennas strung horizontally over the rock formation terminating in low resistance ground terminals at either end. The current flows into the rock and because of the low conductivity of the medium, the signals are driven deep into the earth from one terminal to the other. This effectively produces a loop antenna. The signal radiates into the atmosphere, traveling between the ionosphere and the earth's surface. The signal penetrates the surface of the ocean and propagates to great depths. Clearly, ELF is an attractive transmission mechanism for communicating with submarines. In fact, submarines are the primary ELF communications users. ELF systems decrease the vulnerability of our submarine force as communications are conducted at patrol depths and speeds. ELF possesses two key advantages: 1-3 • Efficient signaling schemes and sophisticated receiver designs help minimize the required transmitter power. Very low radiated power (2 to 8 watts) is required to transmit at great distances. • ELF signals are inherently resistant to the effects of electromagnetic pulses. Nevertheless, there are substantial drawbacks with ELF communications due to factors such as: • Continual setbacks in developing ELF communications occur due to political and environmental debates concerning the potential health hazards although no health or environmental hazards have been substantiated. • ELF transmitting antennas require a large ground plane. Proposed ELF sites will require 134 km of buried antenna. The system cost is both expensive and geographically expansive. • Site selection and antenna design process are always time consuming and have cost factors with which to contend. • The electromagnetic fields produced by ELF transmitter sites may cause interference problems to local power distribution lines and telephone circuits. • ELF communications systems are susceptible to many forms of jamming although signal bandwidth spreading can alleviate the effects. • Data rate transmission is slow. ELF systems, as used today, are intended primarily as a wartime submarine communications system. We can expect to see continued engineering developments in tactical communications with submarines, particularly in the following technical areas: • Propagation phenomena (attenuation, diurnal and seasonal variation weather) • Signal processing in a noise environment • Message pre-formatting and coding techniques due to a slow data rate • Signal bandwidth spreading in order to protect against hostile Electronic Counter Measures (ECM) • Synchronous transmitter operation to increase signal strength and reliability 1-4 1.3 Very Low Frequency (VLF) VLF is the communications band extending from 3 kHz to 30 kHz. VLF radio waves are used for long range communications and navigation. Wave propagation is accomplished via ducting between the earth's surface and the lower ionosphere boundary. VLF has limited use in transmission to points below the sea's surface and on the earth's surface. An important factor in VLF transmission is ground loss resistance. The amount of resistance varies inversely with the total length of wire in the ground system. Hundreds of kilometers of wire are needed to keep ground resistance down to tenths of an ohm. Antennas are vertically polarized. It does however permit world-wide coverage and is relatively insensitive to physical obstacles. Furthermore, propagation is the same over both land and water. However, it requires a very large ground plane and transmitting antenna which characteristically have very low gain. Equipment is typi- cally large and expensive. Also, a large land area is required for the ground plane. This transmission frequency has, nevertheless, been used in Coast Guard applications – the Omega Navigation System operates in the VLF band. The technology required to fur- ther use this radio frequency will continue with the substantial ongoing work being done in the field of submarine communications. 1.4 Low Frequency (LF) Low frequency (30 kHz to 300 kHz) are propagated to distances of a few hundred kilometers by direct-ray diffraction (surface waves) around the curvature of the earth and by indirect wave reflection from the ionosphere. LF systems are normally used for intermediate ranges of 1000 to 5000 km. Surface wave propagation studies indicate that in the LF through HF frequency ranges, field strengths increase with decreasing frequency and are stronger over sea water than over land. Vertical polarization gives higher field strengths than horizontal. Sky waves cause fading at 80 to 800 km distances and generally produce higher- level field strengths than the surface
Load more

Recommended publications
  • A Technical Assessment of Aperture-Coupled Antenna Technology
    Running head: APERTURE-COUPLED ANTENNA TECHNOLOGY 1 A Technical Assessment of Aperture-coupled Antenna Technology Justin Obenchain A Senior Thesis submitted in partial fulfillment of the requirements for graduation in the Honors Program Liberty University Spring 2014 APERTURE-COUPLED ANTENNA TECHNOLOGY 2 Acceptance of Senior Honors Thesis This Senior Honors Thesis is accepted in partial fulfillment of the requirements for graduation from the Honors Program of Liberty University. ______________________________ Carl Pettiford, Ph.D. Thesis Chair ______________________________ Kyung K. Bae, Ph.D. Committee Member ______________________________ James Cook, Ph.D. Committee Member ______________________________ Brenda Ayres, Ph.D. Honors Director ______________________________ Date APERTURE-COUPLED ANTENNA TECHNOLOGY 3 Abstract Aperture coupling refers to a method of construction for patch antennas, which are specific types of microstrip antennas. These antennas are used in a variety of applications including cellular telephones, military radios, and other communications devices. The purpose of this thesis is to assess the benefits and drawbacks of aperture- coupled antenna technology. To develop a successful analysis of the patch antenna construction technique known as aperture coupling, this assessment begins by examining basic antenna theory and patch antenna design. After uncovering some of the fundamental principles that govern aperture-coupled antenna technology, a hypothesis is created and assessed based on the positive and negative aspects
    [Show full text]
  • The Gyrotrons As Promising Radiation Sources for Thz Sensing and Imaging
    applied sciences Review The Gyrotrons as Promising Radiation Sources for THz Sensing and Imaging Toshitaka Idehara 1,2, Svilen Petrov Sabchevski 1,3,* , Mikhail Glyavin 4 and Seitaro Mitsudo 1 1 Research Center for Development of Far-Infrared Region, University of Fukui, Fukui 910-8507, Japan; idehara@fir.u-fukui.ac.jp or [email protected] (T.I.); mitsudo@fir.u-fukui.ac.jp (S.M.) 2 Gyro Tech Co., Ltd., Fukui 910-8507, Japan 3 Institute of Electronics of the Bulgarian Academy of Science, 1784 Sofia, Bulgaria 4 Institute of Applied Physics, Russian Academy of Sciences, 603950 N. Novgorod, Russia; [email protected] * Correspondence: [email protected] Received: 14 January 2020; Accepted: 28 January 2020; Published: 3 February 2020 Abstract: The gyrotrons are powerful sources of coherent radiation that can operate in both pulsed and CW (continuous wave) regimes. Their recent advancement toward higher frequencies reached the terahertz (THz) region and opened the road to many new applications in the broad fields of high-power terahertz science and technologies. Among them are advanced spectroscopic techniques, most notably NMR-DNP (nuclear magnetic resonance with signal enhancement through dynamic nuclear polarization, ESR (electron spin resonance) spectroscopy, precise spectroscopy for measuring the HFS (hyperfine splitting) of positronium, etc. Other prominent applications include materials processing (e.g., thermal treatment as well as the sintering of advanced ceramics), remote detection of concealed radioactive materials, radars, and biological and medical research, just to name a few. Among prospective and emerging applications that utilize the gyrotrons as radiation sources are imaging and sensing for inspection and control in various technological processes (for example, food production, security, etc).
    [Show full text]
  • Radiometry and the Friis Transmission Equation Joseph A
    Radiometry and the Friis transmission equation Joseph A. Shaw Citation: Am. J. Phys. 81, 33 (2013); doi: 10.1119/1.4755780 View online: http://dx.doi.org/10.1119/1.4755780 View Table of Contents: http://ajp.aapt.org/resource/1/AJPIAS/v81/i1 Published by the American Association of Physics Teachers Related Articles The reciprocal relation of mutual inductance in a coupled circuit system Am. J. Phys. 80, 840 (2012) Teaching solar cell I-V characteristics using SPICE Am. J. Phys. 79, 1232 (2011) A digital oscilloscope setup for the measurement of a transistor’s characteristic curves Am. J. Phys. 78, 1425 (2010) A low cost, modular, and physiologically inspired electronic neuron Am. J. Phys. 78, 1297 (2010) Spreadsheet lock-in amplifier Am. J. Phys. 78, 1227 (2010) Additional information on Am. J. Phys. Journal Homepage: http://ajp.aapt.org/ Journal Information: http://ajp.aapt.org/about/about_the_journal Top downloads: http://ajp.aapt.org/most_downloaded Information for Authors: http://ajp.dickinson.edu/Contributors/contGenInfo.html Downloaded 07 Jan 2013 to 153.90.120.11. Redistribution subject to AAPT license or copyright; see http://ajp.aapt.org/authors/copyright_permission Radiometry and the Friis transmission equation Joseph A. Shaw Department of Electrical & Computer Engineering, Montana State University, Bozeman, Montana 59717 (Received 1 July 2011; accepted 13 September 2012) To more effectively tailor courses involving antennas, wireless communications, optics, and applied electromagnetics to a mixed audience of engineering and physics students, the Friis transmission equation—which quantifies the power received in a free-space communication link—is developed from principles of optical radiometry and scalar diffraction.
    [Show full text]
  • Study of CVD Diamond Layers with Amorphous Carbon Admixture by Raman Scattering Spectroscopy
    Materials Science-Poland, 33(4), 2015, pp. 799-805 http://www.materialsscience.pwr.wroc.pl/ DOI: 10.1515/msp-2015-0067 Study of CVD diamond layers with amorphous carbon admixture by Raman scattering spectroscopy ANNA DYCHALSKA1,PIOTR POPIELARSKI2,WOJCIECH FRANKOW´ 2,KAZIMIERZ FABISIAK2,3, KAZIMIERZ PAPROCKI2,MIROSŁAW SZYBOWICZ1∗ 1Faculty of Technical Physics, Poznan University of Technology, Piotrowo 3, 60-965 Poznan,´ Poland 2Institute of Physics, Kazimierz Wielki University, Powstanc´ ow´ Wielkopolskich 2, 85-090 Bydgoszcz, Poland 3Medical Physics Department, Oncology Center, I. Romanowskiej 2, 85-796 Bydgoszcz, Poland Raman spectroscopy is a most often used standard technique for characterization of different carbon materials. In this work we present the Raman spectra of polycrystalline diamond layers of different quality, synthesized by Hot Filament Chemical Vapor Deposition method (HF CVD). We show how to use Raman spectroscopy for the analysis of the Raman bands to deter- mine the structure of diamond films as well as the structure of amorphous carbon admixture. Raman spectroscopy has become an important technique for the analysis of CVD diamond films. The first-order diamond Raman peak at ca. 1332 cm−1 is an unambiguous evidence for the presence of diamond phase in the deposited layer. However, the existence of non-diamond car- bon components in a CVD diamond layer produces several overlapping peaks in the same wavenumber region as the first order diamond peak. The intensities, wavenumber, full width at half maximum (FWHM) of these bands are dependent on quality of diamond layer which is dependent on the deposition conditions. The aim of the present work is to relate the features of diamond Raman spectra to the features of Raman spectra of non-diamond phase admixture and occurrence of other carbon structures in the obtained diamond thin films.
    [Show full text]
  • Silicon Taper Based D-Band Chip to Waveguide Interconnect For
    1 Silicon Taper Based D-band Chip to Waveguide Interconnect for Millimeter-wave Systems Ahmed Hassona, Vessen Vassilev, Zhongxia Simon He, Chiara Mariotti, Franz Dielacher and Herbert Zirath wastes silicon area that can be utilized. Another approach is to Abstract— This paper presents a novel interconnect for use a separate transition [4] [5]. Using a separate transition is coupling Millimeter-wave (mmW) signals from integrated crucial from performance perspective, as coupling the RF circuits to air-filled waveguides. The proposed solution is realized through a slot antenna implemented in embedded Wafer Level signal directly to the MMIC from the waveguide causes Ball Grid Array (eWLB) process. The antenna radiates into a waveguide modes to leak into the circuit cavity and hence high-resistivity (HR) silicon taper perpendicular to its plane, affect performance. The drawback of this solution is that it which in turn radiates into an air-filled waveguide. The requires bondwire connections between the waveguide- interconnect achieves a measured average insertion loss of 3.4 dB transition and the MMIC. Using bondwires at frequencies over the frequency range 116-151 GHz. The proposed interconnect is generic and does not require any galvanic beyond 100 GHz requires special compensation techniques [6] contacts. The utilized eWLB packaging process is suitable for because of the high inductive behavior of bondwires at these low-cost high-volume production and allows heterogeneous frequencies. integration with other technologies. This work proposes a This work addresses mmW system integration challenges by straightforward cost-effective high-performance interconnect for utilizing eWLB packaging technology. eWLB packaging mmW integration and thus addressing one of the main challenges facing systems operating beyond 100 GHz.
    [Show full text]
  • Criteria for Choosing Line Codes in Data Communication
    ISTANBUL UNIVERSITY – YEAR : 2003 (843-857) JOURNAL OF ELECTRICAL & ELECTRONICS ENGINEERING VOLUME : 3 NUMBER : 2 CRITERIA FOR CHOOSING LINE CODES IN DATA COMMUNICATION Demir Öner Istanbul University, Engineering Faculty, Electrical and Electronics Engineering Department Avcılar, 34850, İstanbul, Turkey E-mail: [email protected] ABSTRACT In this paper, line codes used in data communication are investigated. The need for the line codes is emphasized, classification of line codes is presented, coding techniques of widely used line codes are explained with their advantages and disadvantages and criteria for chosing a line code are given. Keywords: Line codes, correlative coding, criteria for chosing line codes.. coding is either performed just before the 1. INTRODUCTION modulation or it is combined with the modulation process. The place of line coding in High-voltage-high-power pulse current The transmission systems is shown in Figure 1. purpose of applying line coding to digital signals before transmission is to reduce the undesirable The line coder at the transmitter and the effects of transmission medium such as noise, corresponding decoder at the receiver must attenuation, distortion and interference and to operate at the transmitted symbol rate. For this ensure reliable transmission by putting the signal reason, epecially for high-speed systems, a into a form that is suitable for the properties of reasonably simple design is usually essential. the transmission medium. For example, a sampled and quantized signal is not in a suitable form for transmission. Such a signal can be put 2. ISSUES TO BE CONSIDERED IN into a more suitable form by coding the LINE CODING quantized samples.
    [Show full text]
  • VHF and UHF Signal Characteristics Observed on a Long Knife-Edge Diffraction Path A
    JOURNAL OF RESEARCH of the National Bureau of Standards- D. Radio Propagatior. Vol. 65D, No. 5, September- Odober 1961 VHF and UHF Signal Characteristics Observed on a Long Knife-Edge Diffraction Path A. P. Barsis and R. S. Kirby (R eceived April 6, 1961) Contribution from Central Radio Propagation Laboratory, National Bureau of Standards, Boulder, Colo. During 1959 and 1960 long-term transmission loss measurements were performed over a 223 kilom eter path in Eastern Colorado using frequencies of 100 and 751 megacycles per second. This path intersects P ikes P eak which forms a knife-edge type obstacle visible from both terminals. The transmission loss measurements have been analyzed in terms of diurnal a nd seaso nal variations in hourly medians and in instan taneous levels. As expected, results show t hat the long-term fading range is substantially less t han expected for t ropospheric seatter paths of comparable length. T ransmission loss levels were in general agreem ent wi t h predicted k ni fe-edge d iffraction propagation when a ll owance is made for rounding of t he knife edge. A technique for est imatin g long-term fading ra nges is presented a nd t he res ults are in good agreement with observations. Short-term variations in some case resemble t he space-wave fadeo uts commonly observed on within- the-horizon paths, a lthough other phe­ nomena may contribute to t he fadin g. Since t he foreground telTain was rough there was no evidence of direct a nd grou nd-refl ected lobe structure.
    [Show full text]
  • EHC 238 Front Pages Final.Fm
    This report contains the collective views of an international group of experts and does not necessarily represent the decisions or the stated policy of the International Commission of Non- Ionizing Radiation Protection, the International Labour Organization, or the World Health Organization. Environmental Health Criteria 238 EXTREMELY LOW FREQUENCY FIELDS Published under the joint sponsorship of the International Labour Organization, the International Commission on Non-Ionizing Radiation Protection, and the World Health Organization. WHO Library Cataloguing-in-Publication Data Extremely low frequency fields. (Environmental health criteria ; 238) 1.Electromagnetic fields. 2.Radiation effects. 3.Risk assessment. 4.Envi- ronmental exposure. I.World Health Organization. II.Inter-Organization Programme for the Sound Management of Chemicals. III.Series. ISBN 978 92 4 157238 5 (NLM classification: QT 34) ISSN 0250-863X © World Health Organization 2007 All rights reserved. Publications of the World Health Organization can be obtained from WHO Press, World Health Organization, 20 Avenue Appia, 1211 Geneva 27, Switzerland (tel.: +41 22 791 3264; fax: +41 22 791 4857; e- mail: [email protected]). Requests for permission to reproduce or translate WHO publications – whether for sale or for noncommercial distribution – should be addressed to WHO Press, at the above address (fax: +41 22 791 4806; e-mail: [email protected]). The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of the World Health Organization concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.
    [Show full text]
  • Applied Engineering Using Schumann Resonance for Earthquakes Monitoring
    applied sciences Article Applied Engineering Using Schumann Resonance for Earthquakes Monitoring Jose A. Gazquez 1,2, Rosa M. Garcia 1,2, Nuria N. Castellano 1,2 ID , Manuel Fernandez-Ros 1,2 ID , Alberto-Jesus Perea-Moreno 3 ID and Francisco Manzano-Agugliaro 1,* ID 1 Department Engineering, University of Almeria, CEIA3, 04120 Almeria, Spain; [email protected] (J.A.G.); [email protected] (R.M.G.); [email protected] (N.N.C.); [email protected] (M.F.-R.) 2 Research Group of Electronic Communications and Telemedicine TIC-019, 04120 Almeria, Spain 3 Department of Applied Physics, University of Cordoba, CEIA3, Campus de Rabanales, 14071 Córdoba, Spain; [email protected] * Correspondence: [email protected]; Tel.: +34-950-015396; Fax: +34-950-015491 Received: 14 September 2017; Accepted: 25 October 2017; Published: 27 October 2017 Abstract: For populations that may be affected, the risks of earthquakes and tsunamis are a major concern worldwide. Therefore, early detection of an event of this type in good time is of the highest priority. The observatories that are capable of detecting Extremely Low Frequency (ELF) waves (<300 Hz) today represent a breakthrough in the early detection and study of such phenomena. In this work, all earthquakes with tsunami associated in history and all existing ELF wave observatories currently located worldwide are represented. It was also noticed how the southern hemisphere lacks coverage in this matter. In this work, the most suitable locations are proposed to cover these geographical areas. Also, ELF data processed obtained from the observatory of the University of Almeria in Calar Alto, Spain are shown.
    [Show full text]
  • Capacity of Flat and Freq.-Selective Fading Channels Linear Digital Modulation Review
    Lecture 8 - EE 359: Wireless Communications - Winter 2020 Capacity of Flat and Freq.-Selective Fading Channels Linear Digital Modulation Review Lecture Outline • Channel Inversion with Fixed Rate Transmission • Comparison of Fading Channel Capacity under Different Schemes • Capacity of Frequency Selective Fading Channels • Review of Linear Digital Modulation • Performance of Linear Modulation in AWGN 1. Channel Inversion with Fixed Rate Transmission • Suboptimal transmission strategy where fading is inverted to maintain constant re- ceived SNR. • Simplifies system design and is used in CDMA systems for power control. • Capacity with channel inversion greatly reduced over that with optimal adaptation (capacity equals zero in Rayleigh fading). • Truncated inversion: performance greatly improved by inverting above a cutoff γ0. 2. Comparison of Fading Channel Capacity under Different Schemes: • Fading generally decreases channel capacity. • Rate/power adaptation have similar capacity as rate adaptation alone. • Rate adaptation alone has same capacity as no adaptation (RX CSI only) but rate adaptation is more practical due to complexity of ML decoding over long blocklengths that experience all fading values. This ML decoding is necesssary to achieve capacity in the RX CSI only case. • Truncated channel inversion is more practical than rate adaptation, with significant capacity gain over full channel inversion, which has zero capacity in Rayleigh fading. 3. Capacity of Frequency Selective Fading Channels • Capacity for time-invariant frequency-selective fading channels is a \water-filling” of power over frequency. • For time-varying ISI channels, capacity is unknown in general. Approximate by di- viding up the bandwidth subbands of width equal to the coherence bandwidth (same premise as multicarrier modulation) with independent fading in each subband.
    [Show full text]
  • The Crossing of Heaven
    The Crossing of Heaven Memoirs of a Mathematician Bearbeitet von Karl Gustafson, Ioannis Antoniou 1. Auflage 2012. Buch. xvi, 176 S. Hardcover ISBN 978 3 642 22557 4 Format (B x L): 15,5 x 23,5 cm Gewicht: 456 g Weitere Fachgebiete > Mathematik > Numerik und Wissenschaftliches Rechnen > Angewandte Mathematik, Mathematische Modelle Zu Inhaltsverzeichnis schnell und portofrei erhältlich bei Die Online-Fachbuchhandlung beck-shop.de ist spezialisiert auf Fachbücher, insbesondere Recht, Steuern und Wirtschaft. Im Sortiment finden Sie alle Medien (Bücher, Zeitschriften, CDs, eBooks, etc.) aller Verlage. Ergänzt wird das Programm durch Services wie Neuerscheinungsdienst oder Zusammenstellungen von Büchern zu Sonderpreisen. Der Shop führt mehr als 8 Millionen Produkte. 4. Computers and Espionage ...and the world’s first spy satellite... It was 1959 and the Cold War was escalating steadily, moving from a state of palpable sustained tension toward the overt threat to global peace to be posed by the 1962 Cuban Missile Crisis – the closest the world has ever come to nuclear war. Quite by chance, I found myself thrust into this vortex, involved in top-level espionage work. I would soon write the software for the world’s first spy satellite. It was a summer romance, in fact, that that led me unwittingly to this particular role in history. In 1958 I had fallen for a stunning young woman from the Washington, D.C., area, who had come out to Boulder for summer school. So while the world was consumed by the escalating political and ideological tensions, nuclear arms competition, and Space Race, I was increasingly consumed by thoughts of Phyllis.
    [Show full text]
  • Additive Synthesis, Amplitude Modulation and Frequency Modulation
    Additive Synthesis, Amplitude Modulation and Frequency Modulation Prof Eduardo R Miranda Varèse-Gastprofessor [email protected] Electronic Music Studio TU Berlin Institute of Communications Research http://www.kgw.tu-berlin.de/ Topics: Additive Synthesis Amplitude Modulation (and Ring Modulation) Frequency Modulation Additive Synthesis • The technique assumes that any periodic waveform can be modelled as a sum sinusoids at various amplitude envelopes and time-varying frequencies. • Works by summing up individually generated sinusoids in order to form a specific sound. Additive Synthesis eg21 Additive Synthesis eg24 • A very powerful and flexible technique. • But it is difficult to control manually and is computationally expensive. • Musical timbres: composed of dozens of time-varying partials. • It requires dozens of oscillators, noise generators and envelopes to obtain convincing simulations of acoustic sounds. • The specification and control of the parameter values for these components are difficult and time consuming. • Alternative approach: tools to obtain the synthesis parameters automatically from the analysis of the spectrum of sampled sounds. Amplitude Modulation • Modulation occurs when some aspect of an audio signal (carrier) varies according to the behaviour of another signal (modulator). • AM = when a modulator drives the amplitude of a carrier. • Simple AM: uses only 2 sinewave oscillators. eg23 • Complex AM: may involve more than 2 signals; or signals other than sinewaves may be employed as carriers and/or modulators. • Two types of AM: a) Classic AM b) Ring Modulation Classic AM • The output from the modulator is added to an offset amplitude value. • If there is no modulation, then the amplitude of the carrier will be equal to the offset.
    [Show full text]