Telecommunications: Past, Present and Future

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Telecommunications Past, Present and Future

• Branimir Vojcic
• ECE Dept, GWU

2
Outline

• Why is telecommunications important?
• History of telecommunications
• What is the state-of-the art?
• What can we expect in the future?

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Telecommunications versus Society/Economy
Service Economy
Knowledge Economy
Manufacturing Economy
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Ancient Communications Systems

• Pigeons
• Messengers
• Optical signals using mirrors and light sources
• Smoke signals

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History of Modern Communications (1)

• 1837 The telegraph was invented by Samuel Morse
  (telegraph distance writing) which marks the
  beginning of electrical communications Morse
  code consists of a dot, a dash, a letter space
  and a word space
• 1864 James Clerk Maxwel formulated the
  electromagnetic theory of light and predicted the
  existence of radio waves

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History of Modern Communications (2)

• 1875 Emile Baudot invented telegraphic code for
  teletypewritters each code word consists of 5
  mark/space symbols (1/0 in todays terminology)
• 1875 Alexander Graham Bell invented the
  telephone for real-time speech transmission (the
  first step-by-step switch was invented in 1897 by
  Strowger)

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History of Modern Communications (3)

• 1887 Heinrich Hertz demonstated the existence of
  radio waves
• 1894 Oliver Lodge demonstrated radio
  communication over short distance (150 yards)
• 1901 Guglielmo Marconi received in Newfoundland
  a radio signal that originated in England (1700
  miles)

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History of Modern Communications (4)

• 1904 John Ambrose Fleming invented the
  vacuum-tube diode
• 1906 Lee de Forest invented the vacuum-tube
  triode
• 1918 Edwin Armstrong invented the
  superheterodyne radio receiver
• 1928 First all-electronic television
  demonstrated by Philo Farnsworth (and then in
  1929 by Vladimir Zworykin) and by 1939 BBC had
  commercial TV broadcasting

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History of Modern Communications (5)

• 1937 Alec Reeves invented pulse-code modulation
  (PCM) for digital encoding of speech signals
• 1943 D.O. North invented the matched filter for
  optimum detection of signals in additive white
  noise
• 1946 The idea of Automatic Repeat-Request (ARQ)
  was published by van Duuren

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History of Modern Communications (6)

• 1947 Kotelnikov developed the geometric
  representation of signals
• 1948 Claude Shannon published A Mathematical
  Theory of Communication
• 1948 The transistor was invented in Bell Labs by
  Walter Brattain, John Bardeen and William
  Shockley
• 1950 Golay and Hamming proposed first
  non-trivial error correcting codes

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History of Modern Communications (7)

• 1957 Soviet Union launched Sputnik I for
  transmission of telemetry signals (satellite
  communications originally proposed by Arthur
  Clark in 1945 and John Pierce in 1955)
• 1958 The first silicon IC was made by Robert
  Noyce
• 1959 The Laser (Light Amplification by
  Stimulated Emission of Radiation) was invented

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History of Modern Communications (8)

• 1960 The first commercial telephone system with
  digital switching
• 1965 Robert Lucky invented adaptive equalization
• 1966 Kao and Hockham of Stanford Telephone
  Laboratories (UK) proposed fiber-optic
  communications
• 1967 Viterbi Algorithm for max. likelihood
  decoding of convolutional codes

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History of Modern Communications (9)

• 1971 ARPANET was put into service
• 1982 Ungerboeck invented trellis coded
  modulation
• 1993 Turbo codes introduced by Berrou, Glavieux
  and Thitimajshima
• Whats next?

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Communication Systems

• An Overview

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Communication Systems
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Model of Communication Systems
DISTORTION NOISE INTERFERENCE
CHANNEL

• COMMUNICATION USING ELECTRICAL AND OPTICAL
  SIGNALS IS
• Fast
• Far reaching
• Economical

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Carried Information
The input messages can be

• SPEECH

• MUSIC

• PICTURES

• VIDEO

• COMPUTER DATA

INPUT MESSAGES ARE TRANSDUCED TO ELECTRICAL OR
OPTICAL SIGNALS IF NECESSARY
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Physical Media
EXAMPLES OF COMMUNICATION CHANNELS ARE

• WIRE

Communication channels are physical media through
which signals propogate.

• COAXIAL CABLE

• WAVEGUIDE

• OPTICAL FIBER

• RADIO LINK

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Communication Channel
Communication channel introduces
DISTORTION
NOISE
INTERFERENCE
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Modulation

• Modulation is the process that modifies the input
  signal into a form appropriate for transmission
  over a communication channel (transmitted signal)
• Typically, the modulation involves varying some
  parameters of a carrier wave in accordance with
  the input signal

• CARRIER

• INPUT SIGNAL

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Modulation Type

• Receiver recovers the input signal from the
  received signal.
• Modulation can be
• ANALOG (Parameter changes of the transmitted
  signal directly follow changes of the input
  signal)
• DIGIGAL (Parameter changes of the transmitted
  signal represent discrete-time finite-precision
  measurements of the input signal)
• Primary communication system design
  considerations
• Transmitted power, Channel bandwidth and Fidelity
  of output message
• Digital communication systems are more efficient
  and reliable

ANALOG MODULATION
DIGITAL MODULATION
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Optical Networks
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Why Optical Transmission?

• Immune to electrical interference
• No radiation
• Low attenuation, long transmission distance
• Less bulky than cables
• Tremendous capacity
• High data rates
• Less maintenance cost

coaxial transmission generally has a bandwidth
limit of 500 MHz. Current fiber optic systems
have not even begun to utilize the enormous
potential bandwidth that is possible.
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Attenuation vs. Frequency
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Attenuation vs. Wavelength
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Attenuation and Dispersion
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Multiplexing
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TDM vs. WDM
TDM
WDM
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Relationship Between WDM TDM
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Optical Devices
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Optical Networks Market (Millions)
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Wireless Networks
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Wireless is Growing Rapidly
Source The Economist Sept. 18-24, 1999
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Traffic Increasingly Consists of Data
Source http//www.qualcomm.com
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Mobile/Cellular Communications
Mobile Station
Base Station
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Cellular Concept

• Every cell corresponds to the service area of one
  Base Station
• Each frequency can be reused in a sufficiently
  distant cell

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Network Architecture
Public Networks
Network Switching Subsystem
Base Station Subsystem
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Ad-Hoc Mobile Internet
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Satellite Communications

• Un-tethered, Global, Broadband, Mobile and
  Ubiquitous.

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Wireless Mobility
Satellite Regional Area
Wide Area
Local Area

• Emerging Connectivity Solutions
• Cellular, Satellite, Microwave, and Packet Radio

SOURCE CISCO
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Satellite Features

• New Wideband Frequency Allocations
• Global Access
• Rapid Deployment
• User Mobility
• Multicasting, Broadcasting
• Bypass and/or Serve Terrestrial Disaster
• High Startup Costs, Lower Incremental Cost

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Existing Systems

• Global and Regional Trunking
• Direct TV Broadcast
• VSAT Networks
• Mobile Satellite Systems (MSS)
• Paging
• Aeronautical/ Maritime
• Global Positioning (GPS and GLONASS)

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Iridium 66 Polar Orbits with spot beams
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Local Area Networks
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Local Area Networks (1)

• A local Area Network provides the interconnection
  of a heterogeneous population of mainframes, work
  stations,personal computers, servers, intelligent
  terminals and peripherals.
• Topologically, LANs connect the devices or
  stations in the form of a bus, a tree, a ring or
  a star configuration.
• Wireline (Token Ring, Ethernet)
• Wireless (802.11, Bluetooth, UWB,)

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Wireless Local Area Networks
Source Proxim
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Local Area Networks
802.11 LAN
802.x LAN
STA1
BSS1
Access Point
Access Point
ESS
BSS2
STA2
STA3
802.11 LAN
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Bluetooth
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LAN Applications

• Client-Server communications
• Shared database access
• Word processing, Electronic mail
• Sharing of mass storage devices, printers and
  other peripherals, software and computational
  resources
• Data exchange between computers and mass storage
  devices
• CAD/CAM, Inventory control, Process control,
  Device control

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A Lesson From the Past
Well Informed people know it is impossible to
transmit the voice over wires and that, were it
possible to do so, the thing would be of no
practical value Excerpt from an 1865 BOSTON
POST editorial