Introduction%20to%20Analog%20And%20Digital%20Communications - PowerPoint PPT Presentation

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Title: Introduction%20to%20Analog%20And%20Digital%20Communications

Introduction to Analog And Digital Communications
Chapter 1 Introduction
  • 1.1 Historical Background
  • 1.2 Applications
  • 1.3 Primary Resources and Operational
  • 1.4 Underpinning Theories of Communication
  • 1.5 Concluding Remarks

To understand a science it is necessary to know
its history -Auguste Comte (1798-1857)
1.1 Historical Background
  • Telegraph
  • 1844, Samuel Morse,
  • What hath God wrought transmitted by Morses
    electric telegraph
  • Washington D.C Baltimore, Maryland
  • Morse code variable-length code (a dot, a dash,
    a letter space, a word space)
  • Radio
  • 1864, James Clerk Maxwell
  • Formulated the electromagnetic theory of light
  • Predicted the existence of radio waves
  • 1887, Heinrich Hertz
  • The existence of radio waves was confirmed
  • 1894, Oliver Lodge
  • Demo wireless communication over a relatively
    short distance (150 yards)

  • 1901, Guglielmo Marconi
  • Demo wireless communication over a long
    distance (1700 miles)
  • 1906, Reginald Fessenden
  • Conducting the first radio broascast
  • 1918, Edwin H. Armstrong
  • Invented the superheterodyne radio receiver
  • 1933, Edwin H. Armstrong
  • Demonstrated another modulation scheme (
    Frequency nodulation)
  • Telephone
  • 1875, Alexander Graham Bell
  • Invented the telephone
  • 1897, A. B. Strowger
  • Devised the autiomatic step-by-step switch

  • Electronics
  • 1904, John Ambrose Eleming
  • Invented the vacuum-tube diode
  • 1906, Lee de Forest
  • Invented the vacuum-tube triode
  • 1948, Walter H. Brattain, William Shockley (Bell
  • Invented the transistor
  • 1958, Robert Noyce
  • The first silicon integrated circuit (IC) produce
  • Television
  • 1928, Philo T. Farnsworth
  • First all-electronic television system
  • 1929, Vladimir K. Zworykin
  • all-electronic television system
  • 1939, BBC
  • Broadcasting television service on a commercial

  • Digital Communications
  • 1928, Harry Nyquist
  • The theory of signal transmission in telegraphy
  • 1937, Alex Reeves
  • Invent pulse-code modulation
  • 1958, (Bell Lab.)
  • First call through a stored-program system
  • 1960, (Morris, Illinois)
  • The first commercial telephone service with
    digital switching begin.
  • 1962, (Bell Lab.)
  • The first T-1 carrier system transmission was
  • 1943, D. O. North
  • Matched filter for the optimum detection of a
    unknown signal in a additive white noise
  • 1948, Claude Shannon
  • The theoretical foundation of digital
    communications were laid

  • Computer Networks
  • 19431946, (Moore School of Electrical
    Engineering of the Univ. of Pennsylvania)
  • ENIAC first electronic digital computer
  • 1950s
  • Computers and terminals started communicating
    with each other
  • 1965, Robert Lucky
  • Idea of adaptive equalization
  • 1982, G. Ungerboeck
  • Efficient modulation techniques
  • 19501970
  • Various studies were made on computer networks
  • 1971
  • Advanced Research Project Agency Network(APRANET)
    first put into service
  • 1985,
  • APRANET was renamed the Internet
  • 1990, Tim Berners-Lee
  • Proposed a hypermedia software interface to
    internet (World Wide Web)

  • Satellite Communications
  • 1945, C. Clark
  • Studied the use of satellite for communications
  • 1955, John R. Pierce
  • Proposed the use of satellite for communications
  • 1957, (Soviet Union)
  • Launched Sputnik I
  • 1958, (United States)
  • Launched Explorer I
  • 1962, (Bell Lab.)
  • Launched Telstar I

  • Optical Communications
  • 1966, K.C. Kao, G. A. Hockham
  • Proposed the use of a clad glass fiber as a
    dielectric waveguide
  • 19591960
  • The laser had been invented and developed

1.2 Applications
  • Broadcasting
  • Which involves the use of a single powerful
    transmitter and numerous receivers that are
    relatively inexpensive to build
  • point-to-point communications
  • In which the communication process takes place
    over a link between a single transmitter and a
    single receiver.

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  • Radio
  • Broadcasting
  • AM and FM radio
  • The voices are transmitted from broadcasting
    stations that operate in our neighborhood
  • Television
  • Transmits visual images and voice
  • Point-to-point communication
  • Satellite communication
  • Built around a satellite in geostationary orbit,
    relies on line-of-sight radio propagation for the
    operation of an uplink and a downlink

  • Communication Networks
  • Consists of the interconnection of a number of
    routers that are made up of intelligent
  • Circuit switching
  • Is usually controlled by a centralized
    hierarchical control mechanism with knowledge of
    the networks entire organization
  • Packet switching
  • Store and forward
  • Any message longer than a specified size is
    subdivided prior to transmission into segments
  • The original message is reassembled at the
    destination on a packet-by-packet basis
  • Advantage
  • When a link has traffic to sent, the link tends
    to be more fully utilized.

  • Data Networks
  • Layer
  • A process or device inside a computer system that
    is designed to perform a specific function
  • Open systems interconnection (OSI) reference
  • The communications and related-connection
    functions are organized as a series of layers
    with well-defined interfaces.
  • Composed of seven layers

  • Internet
  • The applications are carried out independently of
    the technology employed to construct the network
  • By the same token, the network technology is
    capable of evolving without affecting the
  • Internal operation of a subnet is organized in
    two different ways
  • Connected manner where the connections are
    called virtual circuits, in analogy with physical
    circuits set up in a telephone system.
  • Connectionless manner where the independent
    packets are called datagrams, in analogy with

  • Integration of Telephone and Internet
  • VOIPs Quality of service
  • Packet loss ratio
  • the number of packets lost in transport across
    the network to the total number of packets pumped
    into the network
  • Connection delay
  • The time taken for a packet of a particular
    host-to-host connection to transmit across the
  • IN future
  • VOIP will replace private branch exchanges (PBXs)
  • If the loading is always low and response time is
    fast, VOIP telephony may become mainstream and

  • Data Storage
  • The digital domain is preferred over the analog
    domain for the storage of audio and video signals
    for the the following compelling reasons
  • The quality of a digitized audio/video signal,
    measured in terms of frequency response,
    linearity, and noise, is determined by the
    digital-to-analog conversion (DAC) process, the
    parameterization of which is under the designers
  • Once the audio/video signal is digitized, we can
    make use of well-developed and powerful encoding
    techniques for data compression to reduce
    bandwidth, and error-control coding to provide
    protection against the possibility of making
    errors in the course of storage.
  • For most practical applications, the digital
    storage of audio and video signals does not
    degrade with time.
  • Continued improvements in the fabrication of
    integrated circuits used to build CDs and DVDs
    ensure the ever-increasing cost-effectiveness of
    these digital storage devices.

1.3 Primary Resources and Operational Requirements
  • The systems are designed to provide for the
    efficient utilization of the two primary
    communication resources
  • Transmitted power
  • The average power of the transmitted signal
  • Channel bandwidth
  • The width of the passband of the channel
  • Classify communication channel
  • Power-limited channel
  • Wireless channels
  • Satellite channels
  • Deep-space links
  • Band-limited channel
  • Telephone channels
  • Television channels

  • The design of a communication system boils down
    to a tradeoff between signal-to-noise ratio and
    channel bandwidth
  • Improve system performance method
  • Signal-to-noise ratio is increased to accommodate
    a limitation imposed on channel bandwidth
  • Channel bandwidth is increased to accommodate a
    limitation imposed on signal-to-noise ratio.

1.4 Understanding Theories of Communication
  • Modulation Theory
  • Sinusoidal carrier wave
  • Whose amplitude, phase, or frequency is the
    parameter chosen for modification by the
    information-bearing signal
  • Periodic sequence of pulses
  • Whose amplitude, width, or position is the
    parameter chosen for modification by the
    information-bearing signal
  • The issues in modulation theory
  • Time-domain description of the modulation signal.
  • Frequency-domain description of the modulated
  • Detection of the original information-bearing
    signal and evaluation of the effect of noise on
    the receiver.

  • Fourier Analysis
  • Fourier analysis provides the mathematical basis
    for evaluating the following issues
  • Frequency-domain description of a modulated
    signal, including its transmission bandwidth
  • Transmission of a signal through a linear system
    exemplified by a communication channel or filter
  • Correlation between a pair of signals
  • Detection Theory
  • Signal-detection problem
  • The presence of noise
  • Factors such as the unknown phase-shift
    introduced into the carrier wave due to
    transmission of the sinusoidally modulated signal
    over the channel

  • In digital communications, we look at
  • The average probability of symbol error at the
    receiver output
  • The issue of dealing with uncontrollable factors
  • Comparison of one digital modulation scheme
    against another.
  • Probability Theory and Random Processes
  • Probability theory for describing the behavior of
    randomly occurring events in mathematical terms
  • Statistical characterization of random signals
    and noise.

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1.5 Concluding Remarks
  • Communication systems encompass many and highly
    diverse applications
  • Radios, television, wireless communications,
    satellite communications, deep-space
    communications, telephony, data networks,
    Internet, and quite a few others
  • Digital communication has established itself as
    the dominant form of communication. Much of the
    progress that we have witnessed in the
    advancement of digital communication systems can
    be traced to certain enabling theories and
  • The study of communication systems is a dynamic
    discipline, continually evolving by exploiting
    new technological innovations in other
    disciplines and responding to new societal needs.
  • Last but by no means least, communication systems
    touch out daily lives both at home and in the
    workplace, and our lives would be much poorer
    without the wide availability of communication
    devices that we take for granted.
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