Post on 03-Jan-2016
description
Fundamentals of Communication Systems (0701454)
Second Semester 2010/2011
Dr. Ali JamoosEmail: ali@eng.alquds.edu
Web site: http://mail.alquds.edu/~f2095/
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Historical Background
1844 – The Telegraph was invented by Samuel Morse
1864 – James Clerk Maxwell formulated the electromagnetic theory
1875 – The Telephone was invented by Alexander Graham Bell
1887 – Heinrich Hertz confirmed the existence of radio waves
1901 – Marconi received a radio signal, 1700 miles across the Atlantic
1904 – John Ambrose Fleming invented the vacuum-tube diode
1906 – John Ambrose Fleming invented the vacuum-tube triode
1918 – Edwin Armstrong invented the superheterodyne radio receiver
1928 – The Television system was demonstrated by Philo Farnsworth
1933 – Edwin Armstrong demonstrated the Frequency Modulation (FM)
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Historical Background
1946 – The first computer, ENIAC, was built at Pennsylvania university
1948 – The transistor was invented at Bell Laboratories
1958 – The first Integrated Circuit (IC) was produced by Robert Noyce
1962 – The Telstar satellite, built by Bell Laboratories, was lunched
1971 – The first computer network, called the ARPANET, was built
1985 – The ARPANET was renamed the Internet
1983 - Advanced Mobile Phone System (AMPS) was lunched in US
1991 - Global System for Mobile (GSM) was lunched in Europe
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A communication Model
• Source - generates data to be transmitted, examples are telephones and computers• Transmitter - converts data into transmittable signals• Transmission System - carries data from source to destination• Receiver - converts received signal into data• Destination - takes incoming data
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Communications Tasks
Transmission system utilization Addressing
Interfacing Routing
Signal generation Recovery
Synchronization Message formatting
Exchange management Security
Error detection and correction Network management
Flow control
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Data Communication Model
1. user keys in message m comprising bits g buffered in source PC memory2. input data is transferred to I/O device (transmitter) as sequence of bits g(t) using
voltage shifts3. transmitter converts these into a signal s(t) suitable for transmission media being
used4. whilst transiting media signal may be impaired so received signal r(t) may differ
from s(t)5. receiver decodes signal recovering g’(t) as estimate of original g(t)6. which is buffered in destination PC memory as bits g’ being the received message
m’
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Elements of digital communication systems
Source of
Information
Source
encoder
Channel
encoderModulator
Channel
User of
information
Source
decoder
Channel
decoderDemodulato
r
Noise and interference
(Unwanted signals)
1. The information source generate a message signal2. The source encoder removes redundant information from the message signal and
produce a source code word3. The channel encoder add some bits for the purpose of error detection and
correction and produce the channel code word4. The modulator represent each symbol of the channel code word by a
corresponding analog symbols (resulting in signal waveform) suitable for the transmission through the channel
5. Noise and interfering signals corrupt the transmitted signal in the channel6. Channel types: guided media (twisted pair, coaxial, fiber optic), unguided
(wireless)7. At the receiver, the received signal is processed in reverse order to that in the
transmitter so as to recover the message signal
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Cellular telephone system
The cellular mobile telephone system consists of:The cellular mobile telephone system consists of: Mobile Stations (MS), Base Stations (BS) and Mobile Switching Mobile Stations (MS), Base Stations (BS) and Mobile Switching Center Center (MSC), connected to the Public Switching Telephone Network (MSC), connected to the Public Switching Telephone Network (PSTN)(PSTN)
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Satellite Communication system
The information-bearing signal is transmitted from the earth terminal to the satellite via the uplink, amplified by the transponder (electronic circuitry on board of the satellite), and then retransmitted from the satellite via the downlink to the other earth terminal
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Computer Networks and the Internet
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OSI Network Model
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Electromagnetic Spectrum
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Electromagnetic wavelength, frequency and photon energy
The electromagnetic wave at a particular wavelength λ has an associated frequency f and photon energy E :
where
is the light speed
Planck’s constant
hchfE
f
c
smc /103 8
GHzeVsJh /13567.4.10626.6 34
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Operating frequency of various guided and unguided transmission techniques
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Atmospheric Transparency for Electromagnetic waves
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Electromagnetic Spectrum
BandBand Frequency Frequency rangerange
Propagation Propagation characteristicscharacteristics
Typical useTypical use
ELF (extremely low frequency) 30 to 300 Hz Ground Wave (GW) Ground Wave (GW) propagationpropagation
Power line frequencies
VF (voice frequency) 300 to 3000 Hz GW propagationGW propagation Used by the telephone system for analogsubscriber lines
VLF (very low frequency) 3 to 30 kHz GW propagationGW propagation Long-range navigation; submarine communication
LF (low frequency) 30 to 300 kHz GW propagationGW propagation Long-range navigation; marine communication
MF (medium frequency) 300 to 3000 kHz
Sky-Wave (SW) ionospheric propagation
AM broadcasting
HF (high frequency) 3 to 30 MHz SW ionospheric propagation international broadcasting,military communication; long-distance aircraft and ship communication
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Electromagnetic Spectrum
BandBand Frequency Frequency rangerange
Propagation Propagation characteristicscharacteristics
Typical useTypical use
VHF (very high frequency) 30 to 300 MHz SW ionospheric and tropospheric propagation;Line-Of-Sight (LOS) Propagation
VHF television; FM broadcast AM aircraft communication; Aircraft navigational aids
UHF (ultra high frequency) 300 to 3000 MHz
LOS Propagation UHF television; cellular telephone; radar; microwave links; personal communications systems
SHF (super high frequency) 3 to 30 GHz LOS PropagationLOS Propagation Satellite communication; Satellite communication; radar; terrestrial radar; terrestrial microwave links; wireless microwave links; wireless local looplocal loop
EHF (extremely high frequency)
30 to 300 GHz LOS PropagationLOS Propagation Experimental; wireless local loop
Infrared 300 GHz to 400 THz
LOS PropagationLOS Propagation Infrared LANs; consumer electronic applications
Visible lightVisible light 400 THz to 900 400 THz to 900 THzTHz
LOS PropagationLOS Propagation Optical communicationOptical communication