Telecommunication i (sec 1.0 & 2.0)

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Telecommunications-I Spring 2015

Transcript of Telecommunication i (sec 1.0 & 2.0)

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Telecommunications-I

Spring 2015

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Section 1.0 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/EconomyComment “Why engineering is nothing without 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 today’s 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: Kotel’nikov 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

• What’s next?

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Wireless History1901: First radio reception across the Atlantic Ocean

1924: First Mobile Radio Telephone

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Signal• How will u define term “Signal”?• How many domains of signal by appearance there?• How signal graphically represented?• How signal mathematically represented?

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Parameters of Signal

Analog Signal

• Amplitude• Wavelength• Frequency• Time Period

• Phase Angle

Digital Signal

• Amplitude• Bit rate

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Section 2.0Communication Systems

An Overview

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Communication Systems

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Bandwidth and spectrum of communication system

• Bandwidth refers to what?• Spectrum defines?• Human voice frequency band?• Human ear can detect sound range?• Bandwidth for a wired communication channel? (like

in landline system)

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Communication Systems

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CHANNELDISTORTION

NOISEINTERFERENCE

INPUT TRANSDUCER TRANSMITTER

INPUTMESSAGE

INPUTSIGNAL

TRANSMITTEDSIGNAL

RECEIVEROUTPUT TRANSDUCER

OUTPUTMESSAGE

OUTPUTSIGNAL

RECEIVEDSIGNAL

Model of Communication Systems

Basically Communication model is comprised of 3 main entities

• Transmitter (Source)• Medium / channel (Wired/wireless)• Receiver (Destination)

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Difference Between Transducer & Transcoder?

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Difference between Amplifier and regenerator