DATA COMMUNICATION ( ela …)
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DATA COMMUNICATION (ELA…) TRANSMISSION MEDIA 1
description
DATA COMMUNICATION ( ela …). TRANSMISSION MEDIA. Transmission Media - Overview. Transmission Medium Physical path between transmitter and receiver Guided Media Waves are guided along a solid medium Unguided Media Provides means of transmission but does not guide electromagnetic signals - PowerPoint PPT Presentation
Transcript of DATA COMMUNICATION ( ela …)
DATA COMMUNICATION(ELA…)
TRANSMISSION MEDIA1
TRANSMISSION MEDIA - OVERVIEW
Transmission MediumPhysical path between transmitter and
receiver Guided Media
Waves are guided along a solid medium
Unguided MediaProvides means of transmission but does not
guide electromagnetic signalsEmploy an antenna for transmission 2
TRANSMISSION MEDIA - OVERVIEW
Characteristics and quality determined by medium and signal
For guided
For unguided
Key concerns are3
DESIGN FACTORS Bandwidth
All other factors remaining constant, higher bandwidth gives higher data rate
Transmission impairmentsAttenuation
Interference Number of receivers
In guided mediaMore receivers (multi-point) introduce
more attenuation
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ELECTROMAGNETIC SPECTRUM
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TRANSMISSION CHARACTERISTICS Guided Media
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FrequencyRange
Typical Attenuation
Typical Delay
Repeater Spacing
Twisted Pair (with loading)
0 to 3.5 kHz 0.2 db/km @ 1 kHz
50 ms/km
2 km
Twisted Pair (multi-pair cables)
0 to 1 MHz 0.7 db/km @ 1 kHz
5 ms/km 2 km
Coaxial cable
0 to 500 MHz 7 db/km @ 10 MHz
4 ms/km 1 to 9km
Optical fiber
186 to 370 THz
0.2 to 0.5 db/km
5 ms/km 40 km
TRANSMISSION MEDIA Guided media
Twisted-pair Coaxial Cable Optical Fiber
Unguided media Satellites Terrestrial Microwave Broadcast Radio
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GUIDED TRANSMISSION MEDIA Transmission Capacity
Either in terms of Bandwidth, or Data Rate
Depends critically on Distance Type of medium
Point-to-point Mutipoint
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TWISTED PAIR
Most common medium Two insulated wires twisted together in a
helical manner (like DNA) Advantages
Disadvantages
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TWISTED PAIR Separately insulated Often bundled into cables Usually installed in buildings during
construction
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TWISTED PAIR - APPLICATIONS Telephone network
Between house and local exchange Within buildings
To private branch exchange (PBX) For local area networks (LAN)
10 Mbps or 100 Mbps
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TWISTED PAIR - TRANSMISSION CHARACTERISTICS
Analog Amplifiers every 5 km to 6 km
DigitalUse either analog or digital signalsRepeater every 2 km or 3 km
Limited inDistanceBandwidth (1 MHz)Data rate (100 Mbps)
Susceptible to interference and noise12
UNSHIELDED AND SHIELDED TP Unshielded Twisted Pair (UTP)
Ordinary telephone wireCheapestEasiest to installSuffers from external Electromagnetic (EM)
interference Shielded Twisted Pair (STP)
Metal braid or sheathing that reduces interference
More expensiveHarder to handle (thick, heavy)
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UTP VS. STP
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UTP CATEGORIES Cat 3
Up to 16 MHzVoice grade found in most officesTwist length of 7.5 cm to 10 cm
Cat 4Up to 20 MHz
Cat 5Up to 100 MHzCommonly pre-installed in new office
buildingsTwist length 0.6 cm to 0.85 cm 15
COMPARISON OF UTP & STP
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Attenuation (dB per 100 m) Near-end Crosstalk (dB)
Frequency(MHz)
Category 3UTP
Category 5UTP 150-ohm STP
Category 3UTP
Category 5UTP 150-ohm STP
1 2.6 2.0 1.1 41 62 58
4 5.6 4.1 2.2 32 53 58
16 13.1 8.2 4.4 23 44 50.4
25 — 10.4 6.2 — 41 47.5
100 — 22.0 12.3 — 32 38.5
300 — — 21.4 — — 31.3
Category 3Class C
Category 5Class D
Category 5E Category 6Class E
Category 7Class F
Bandwidth 16 MHz 100 MHz 100 MHz 200 MHz 600 MHz
Cable Type UTP UTP/FTP UTP/FTP UTP/FTP SSTP
Link Cost(Cat 5 =1)
0.7 1 1.2 1.5 2.2
NEAR END CROSSTALK (NEXT) Coupling of signal from one pair to
another The tighter the twist in the cable, the
more effective the cancellation
17http://www.cabletesting.com
COAXIAL CABLE APPLICATIONS Most versatile medium
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COAXIAL CABLE APPLICATIONS Television distribution
Cable TV Long distance telephone transmission
Can carry 10,000 voice calls simultaneously Being replaced by fiber optic
Short distance computer systems links LANs
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COAXIAL CABLE - TRANSMISSION CHARACTERISTICS Analog
Amplifiers every few km Closer if higher frequency Up to 500 MHz
Digital Repeater every 1 km Closer for higher data rates
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OPTICAL FIBER Greater capacity
Data rates of hundreds of Gbps Smaller size & weight Lower attenuation Electromagnetic isolation Greater repeater spacing
10s of km at least
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OPTICAL FIBER System components:
Transmission medium - fiber optic cable Light source - LED or laser diode Detector - photodiode
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OPTICAL FIBER - APPLICATIONS Telephone Network Applications
Long-haul, metropolitan, rural, and subscriber loop circuits
Local Area Networks Optical fiber networks Data rates from 100 Mbps to 1 Gbps Support hundreds (or even thousands) of
stations
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OPTICAL FIBER - TRANSMISSION CHARACTERISTICS Light Sources
Light Emitting Diode (LED) Cheaper Wider operating temp range Last longer
Injection Laser Diode (ILD) More efficient Greater data rate
Wavelength Division Multiplexing
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ATTENUATION IN GUIDED MEDIA
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