1. Fundamentals of Telecommunication
ICT – TE - BVF- 4.1
Hassan Mesfer ICT-TE-7
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2. Lecture 3 Transmission Media
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3. Overview Physical path between transmitter and receiver Guided - wire
Unguided - wireless
Characteristics and quality of a data transmission determined by medium and signal
For guided, the medium is more important
For unguided, the bandwidth produced by the antenna is more important (directionality)
In designing of data transmission systems
Key concerns are data rate and distance (greater better)
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4. Design Factors Bandwidth Transmission impairments Interference
Higher bandwidth gives higher data rate
Transmission impairments
Attenuation, limits the distance
Interference
From competing signals in overlapping frequency bands
Number of receivers
In guided media
More receivers (multi-point) introduce more attenuation
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5. Electromagnetic Spectrum

6. Guided Transmission Media
Twisted Pair
Coaxial cable
Optical fiber
The transmission capacity depends on:
Distance
Point-to-point or multipoint
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7. Transmission Characteristics of Guided Media
Point-to-point applications
Frequency Range
Typical Attenuation
Typical Delay
Repeater Spacing
Twisted pair (with loading)
0 to 3.5 kHz
0.2 1 kHz
50 µs/km
2 km
Twisted pairs (multi-pair cables)
0 to 1 MHz
0.7 1 kHz
5 µs/km
Coaxial cable
0 to 500 MHz
7 10 MHz
4 µs/km
1 to 9 km
Optical fiber
186 to 370 THz
0.2 to 0.5 dB/km
40 km
W. Stalling, 7th Edition
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8. Unshielded Twisted-Pair Cable
Unshielded twisted-pair cable (UTP) is a four-pair wire medium
Each of the 8 individual copper wires in the UTP cable is covered by insulating material.
In addition, each pair of wires is twisted around each other.
This type of cable relies solely on the cancellation effect produced by the twisted wire pairs, to limit signal degradation caused by EMI and RFI.
CAT 5e is the one most frequently recommended and implemented in installations today.
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9. Twisted Pair
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10. UTP Pros and Cons Unshielded twisted-pair cable has many advantages.
It is easy to install
Less expensive than other types of networking media.
However, the real advantage is the size.
Small external diameter, UTP does not fill up wiring ducts as rapidly as other types of cable.
Disandvantages:
Low data rate
Short range
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11. Unshielded Twisted Pair
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12. Twisted Pair - Applications
Most common
Telephone network
Between house and local exchange (subscriber loop)
Within buildings
To private branch exchange (PBX)
For local area networks (LAN)
10Mbps or 100Mbps
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13. Twisted Pair - Transmission Characteristics
Analog
Amplifiers every 5km to 6km
Digital
Use either analog or digital signals
Repeater every 2km or 3km
Limited distance
Limited bandwidth (1MHz)
Limited data rate (100MHz)
Susceptible to interference and noise
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14. Near End Crosstalk Coupling of signal from one pair to another
Coupling takes place when transmit signal entering the link couples back to receiving pair
i.e. near transmitted signal is picked up by near receiving pair
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15. UTP Categories Cat 3 Cat 4 Cat 5 Cat 5E (Enhanced)
Up to 16MHz
Voice grade found in most offices
Twist length of 7.5 cm to 10 cm
Cat 4
Up to 20 MHz
Cat 5
Up to 100MHz
Commonly pre-installed in new office buildings
Twist length 0.6 cm to 0.85 cm
Cat 5E (Enhanced)
Cat 6 - up to 200MHz
Cat 7 - up to 600MHz
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16. Shielded Twisted-Pair Cable
Shielded twisted-pair cable (STP) combines the techniques of shielding, cancellation, and twisting of wires.
Each pair of wires is wrapped in metallic foil.
The four pairs of wires are wrapped in an overall metallic braid or foil.
STP affords greater protection from all types of external interference, but is more expensive and difficult to install than UTP.
The metallic shielding materials in STP need to be grounded at both ends.
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17. Shielded Twisted-Pair Cable
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18. Unshielded and Shielded TP
Unshielded Twisted Pair (UTP)
Ordinary telephone wire
Cheapest
Easiest to install
Suffers from external EM interference
Shielded Twisted Pair (STP)
Metal braid or sheathing that reduces interference
More expensive
Harder to handle (thick, heavy)
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19. Coaxial Cable
Coaxial Cable consists of a hollow outer cylindrical conductor that surrounds a single inner wire made of two conducting elements.
One of these elements, located in the center of the cable, is a copper conductor.
Surrounding the copper conductor is a layer of flexible insulation.
Over this insulating material is a copper braid or metallic foil that acts as the second wire in the circuit and as a shield for the inner conductor.
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20. Coaxial Cable
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21. Coaxial Cable Speed and Throughput : 10-100 Mbps
Average cost per node : inexpensive
Media and connector type : Medium
Maximum cable length : 500m
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22. Coaxial Cable Applications
Most versatile medium
Television distribution
Ariel to TV
Cable TV
Long distance telephone transmission
Can carry 10,000 voice calls simultaneously
Being replaced by fiber optic
Short distance computer systems links
Local area networks
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23. Coaxial Cable Applications
For LANs, Coaxial Cable offers several advantages.
It can be run longer distances than shielded twisted pair, STP, and unshielded twisted pair, UTP, cable without the need for repeaters.
Coaxial Cable is less expensive than fiber-optic cable, and the technology is well known.
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24. Coaxial Cable - Transmission Characteristics
Analog
Amplifiers every few km
Closer if higher frequency
Up to 500MHz
Digital
Repeater every 1km
Closer for higher data rates
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25. Optical Fiber
Fiber Optics are cables that are made of optical fibers that can transmit large amounts of information at the speed of light.
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26. Optical Fiber
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27. Optical Fiber
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28. Optical Fiber
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29. Optical Fiber - Benefits
Greater capacity
Data rates of hundreds of Gbps
Smaller size and weight
Lower attenuation
Electromagnetic isolation
Greater repeater spacing
10s of km at least
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30. Optical Fiber - Applications
Telephones
Internet
LANs - local area networks
CATV - for video, voice and Internet connections
Long-haul trunks
Metropolitan trunks
Rural exchange trunks
Subscriber loops
Security - closed-circuit TV
Military - everywhere!
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31. Optical Fiber - Transmission Characteristics
Act as wave guide for 1014 to 1015 Hz
Portions of infrared and visible spectrum
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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32. Wireless Transmission Frequencies
2G Hz to 40 GHz
Microwave
Highly directional
Point to point
Satellite
30M Hz to 1 GHz
Omnidirectional
Broadcast radio
3 x 1011 to 2 x 1014
Infrared
Local
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33. Broadcast Radio Omnidirectional FM radio UHF and VHF television
Line of sight
Suffers from multipath interference
Reflections
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34. Infrared Modulate noncoherent infrared light
Line of sight (or reflection)
Blocked by walls
e.g. TV remote control, IRD port
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35. Wireless Propagation Signal travels along three routes Ground wave
Follows contour of earth
Up to 2MHz
AM radio
Sky wave
Amateur radio, BBC world service, Voice of America
Signal reflected from ionosphere layer of upper atmosphere
(Actually refracted)
Line of sight
Above 30Mhz
May be further than optical line of sight due to refraction
More later…
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36. Ground Wave Propagation
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37. Sky Wave Propagation b) Sky-wave propagation 2 -30 MHz 27/04/2017
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38. Line of Sight Propagation
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39. Line of Sight Transmission
Free space loss
Signal disperses with distance
Greater for lower frequencies (longer wavelengths)
Atmospheric Absorption
Water vapour and oxygen absorb radio signals
Water greatest at 22GHz, less below 15GHz
Oxygen greater at 60GHz, less below 30GHz
Rain and fog scatter radio waves
Multipath
Better to get line of sight if possible
Signal can be reflected causing multiple copies to be received
May be no direct signal at all
May reinforce or cancel direct signal
Refraction
May result in partial or total loss of signal at receiver

40. Free Space Loss

41. Multipath Interference
Microwave line of sight
Mobile radio
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