introdution to analog and digital communication


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introdution to analog and digital communication

  1. 1. Introduction to Analog And DigitalCommunications Second Edition Simon Haykin, Michael Moher
  2. 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. 3. 1.1 Historical Background Telegraph  1844, Samuel Morse,  “What hath God wrought” transmitted by Morse’s 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) 3
  4. 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 4
  5. 5.  Electronics  1904, John Abbrose 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 5
  6. 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 6
  7. 7.  Computer Networks  1943~1946, (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  1950~1970  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) 7
  8. 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 8
  9. 9.  Optical Communications  1966, K.C. Kao, G. A. Hockham  Proposed the use of a clad glass fiber as a dielectric waveguide  1959~1960  The laser had been invented and developed 9
  10. 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. 10
  11. 11.  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 11
  12. 12. Back Next 12
  13. 13.  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 network’s 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. 13
  14. 14. Back Next 14
  15. 15.  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 15
  16. 16. Back Next 16
  17. 17.  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. 17
  18. 18. Back Next 18
  19. 19.  Integration of Telephone and Internet  VOIP’s 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 19
  20. 20.  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 1) 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 designer’s control. 2) 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. 3) For most practical applications, the digital storage of audio and video signals does not degrade with time. 4) 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. 20
  21. 21. 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 21
  22. 22.  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. 22
  23. 23. 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. 23
  24. 24.  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 24
  25. 25.  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. 25
  26. 26. 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. 26