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