Download Telecommunications and Video Systems

Telecommunications and Video Systems
Weeks
1--6
Lecture/Tuto Ya Bao
7--12
Vincent Siyau
rial/Lab
Contents
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•
•
•
•
TVS, By Ya Bao
Introduction to
•
telecommunications and
video systems
Modulation and radio
•
broadcast;
Telephone set and
subscriber loop interface;
Telephone network;
Voice over Internet
protocol, ADSL and cable
telephony.
Basic TV
systems and
standards
Multimedia
communicati
ons & basic
video/image
processing
1
ASSESMENT OF THE UNIT
• There will be one 2-hour written examination
(70%), and laboratory assessed work (30%).
• Deadline of submission 4 May. 2007 .
• CORE MATERIALS
Schweber, W., Electronic Communication
Systems: A Complete Course, 4/e Prentice Hall,
2002, ISBN: 0-13-091621-8
http://eent3.sbu.ac.uk/staff/baoyb/TVS
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1. Introduction to communication systems
1.1 What is telecommunications

Communication

Telecommunications
1.2 Development of telecommunications
•
1837
telegraph
S.Morse
•
1876
telephone
A. Bell
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1894
radio communications G. Marconi
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1915
transcontinental telephone line
•
1948
first transistor
•
1962
first communication satellite
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1963
first laser
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60’s
optical fibres, IC, PCM
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70’s
computer net, microprocessor
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80’s
cellular telephone, Internet
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90’s
GPS, ATM, ISDN, GSM
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21 Century
3G, Broad access, DAB radio, digital and HD TV,
WLAN, 4G, ...
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1.3 The block diagram of a communication system
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2. The Electromagnetic Spectrum
2.1 Electromagnetic Waves and Energy
• wavelength: distance between peaks
• velocity: speed at which the energy travels through
• frequency: the number of oscillations or cycles per
second (hertz, abbreviated Hz) of the waveform
• Wavelength: the distance between peaks of the
oscillations of the energy wave
velocity
wavelength 
frequency
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Wavelength can also be measured as the
distance between the negative peaks, zero
points,
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• speed of light: c  3  108 m / s
• The propagation velocity is less in any medium
other than vacuum
• In wire, it is anywhere from 60% to 85% of c
• a common type of cable used for cable TV has
a propagation factor of 75% of c.
Example 1
What is the wavelength in vacuum for a
frequency of 1 million hertz?
Example 2
What is the frequency when the measured
wavelength is 6 m?
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2.2 The Electromagnetic Spectrum
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TABLE 1-1 CCIR Band Designations
Frequency Range
Designations
--------------------------------------------------30 Hz-----300 Hz
ELF
0.3 kHz---3 kHz
VF
3 kHz------30 kHz
VLF
30 kHz----300 kHz
LF
0.3 MHz--3 MHz
MF
3 MHz-----30 MHz
HF
30 MHz---300 MHz
VHF
0.3 GHz---3 GHz
UHF
3 GHz-----30 GHz
SHF
30 GHz----300 GHz
EHF
0.3 THz----3 THz
Infrared light
3 THz-------30 THz
Infrared light
30 THz-----300 THz
Infrared light
0.3 PHz----3 PHz
Visible light
3 PHz------30 PHz
Ultraviolet light
30 PHz-----300 PHz
X-rays
0.3 EHz----3 EHz
Gamma rays
3 EHz-------30 EHz
Cosmic rays
1 kilohertz (kHz)= 103 Hz, 1 megahertz (MHz)= 1*106 Hz 1 gigahertz (GHz)= 1*109 Hz,
1012 : terahertz (THz);
1015 : petahertz (PHz);
1018 : exahertz (EHz);
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2.3 BANDWIDTH AND INFORMATION CAPACITY
• Bandwidth: Bandwidth is the span of
frequencies within the spectrum occupied by a
signal and used by the signal for conveying
information.
• To send more information in a short time
requires more bandwidth.
signalpower
capacity  bandwidth  log 2 (1 
)
nosiepower
Example
Suppose that a communications link is using a transmitter of 10 W power,
and there is 1 W of noise power in the same link. The available bandwidth is
1 kHz. What is the channel capacity?
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2.4 SIMPLEX, DUPLEX, AND
HALF-DUPLEX SYSTEMS
• SIMPLEX: one direction only
• DUPLEX: both directions at a time
• HALF-DUPLEX: either direction, but only
one direction at a time
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2.5 TIME AND FREQUENCY DOMAINS
• Description of a signal versus time --time-domain representation
• Description of a signal versus frequency -frequency-domain representation
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