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

1
Introduction to Analog And Digital Communications
2
Chapter 1 Introduction

• 1.1 Historical Background
• 1.2 Applications
• 1.3 Primary Resources and Operational
  Requirements
• 1.4 Underpinning Theories of Communication
  Systems
• 1.5 Concluding Remarks

To understand a science it is necessary to know
its history -Auguste Comte (1798-1857)
3
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
  experimentally
• 1894, Oliver Lodge
• Demo wireless communication over a relatively
  short distance (150 yards)

4

• 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

5

• 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
  Lab.)
• 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
  basis

6

• 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
  installed
• 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

7

• 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)

8

• 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

9

• 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

10
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.

11
(No Transcript)
12
(No Transcript)
13
(No Transcript)
14
(No Transcript)
15
(No Transcript)
16
(No Transcript)
17
(No Transcript)
18
(No Transcript)
19

• 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

20
Back
Next
21

• Communication Networks
• Consists of the interconnection of a number of
  routers that are made up of intelligent
  processors
• 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.

22
Back
Next
23

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

24
Back
Next
25

• 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
  applications.
• 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
  telegrams.

26
Back
Next
27

• 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
  network
• 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
  widespread

28

• 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
  control.
• 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.

29
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

30

• 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.

31
1.4 Understanding Theories of Communication
Systems

• 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
  signal
• Detection of the original information-bearing
  signal and evaluation of the effect of noise on
  the receiver.

32

• 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

33

• 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.

34
(No Transcript)
35
(No Transcript)
36
(No Transcript)
37
(No Transcript)
38
(No Transcript)
39
(No Transcript)
40
(No Transcript)
41
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
  technologies.
• 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.