1. Chapter 7. Transmission Media
Guided Media
Unguided Media: Wireless
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2. Transmission Medium & Physical Layer
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3. Classes of Transmission Media
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4. Data Communications, Kwangwoon University
Twisted-pair Cable
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5. Data Communications, Kwangwoon University
UTP and STP Cables
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6. Categories of UTP Cables
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7. Data Communications, Kwangwoon University
UTP Connector
RJ45 (RJ stands for registered jack)
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8. Data Communications, Kwangwoon University
UTP Performance
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9. Data Communications, Kwangwoon University
Parallel Flat Wire
Electromagnetic interference can create noise
The noise over parallel wires results in an uneven load and a damaged signal
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10. Noise Effect on Twisted-Pair
Cumulative effect of noise is equal on both sides
Twisting does not always eliminate the noise, but does significantly reduce it
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11. Data Communications, Kwangwoon University
Coaxial Cable
Carries signals of higher frequency ranges than those in twisted-pair cable
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12. Categories of Coaxial Cables
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13. Data Communications, Kwangwoon University
BNC Connectors
Bayone-Neil-Concelman (BNC) connector
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14. Coaxial Cable Performance
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15. Data Communications, Kwangwoon University
Optical Fiber
Optical fiber is made of glass or plastic
It transmits signals in the form of light
The Nature of Light
The speed of light
300,000 Km/sec in a vacuum
Depends on the density of the medium through which it is traveling
Other properties of light
Refraction, Critical angle, Reflection
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16. Data Communications, Kwangwoon University
Bending of Light Ray
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17. Data Communications, Kwangwoon University
Optical Fiber
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18. Data Communications, Kwangwoon University
Propagation Modes
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19. Data Communications, Kwangwoon University
Modes
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20. Data Communications, Kwangwoon University
Fiber Types
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21. Data Communications, Kwangwoon University
Fiber Construction
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22. Fiber-optic Cable Connectors
SC (subscriber channel) connector used for cable TV. It uses push/pull locking system
ST (straight-tip) connector used for connecting cable to networking device. It uses a reliable bayonet locking system
MT-RJ is the same size as RJ45
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23. Optical Fiber Performance
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24. Advantages/Disadvantages of Optical Fiber
Higher bandwidth
Less signal attenuation
Immunity to electromagnetic interference
Resistance to corrosive materials
Light weight
Greater immunity to tapping
Disadvantages
Installation and maintenance
Unidirectional light propagation
Cost
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25. Electromagnetic Spectrum for wireless
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26. Data Communications, Kwangwoon University
Propagation Methods
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27. Data Communications, Kwangwoon University
Bands
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28. Wireless Transmission Waves
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29. Wireless Transmission Waves
Radio waves are used for multicast communications, such as radio and television, and paging systems
Microwaves are used for unicast communication such as cellular telephones, satellite networks, and wireless LANs
Infrared signals can be used for short-range communication in a closed area using line-of-sight propagation
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30. Omnidirectional & Unidirectional Antennas
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31. Data Communications, Kwangwoon University
Infrared
Infrared waves with frequencies from 300 GHz to 400 THz for short-range communication in a closed area using line-of-sight propagation
Having high frequencies, it cannot penetrate walls
IrDA (Infrared Data Association) for standards
Example: IrDA port for wireless keyboard
Originally defined a data rate of 75 kbps for a distance up to 8 m
Recent standard for a data rate of 4 Mbps
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