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Chapter 7
Transmission Media
長庚大學資訊工程學系 陳仁暉 副教授Tel: (03) 211-8800 Ext: 5990
Email: [email protected]:
http://www.csie.cgu.edu.tw/~jhchen
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Figure 7.1 Transmission medium and physical layer
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Transmission Media
• By definition– Broadly defined as anything that can carry information
from a source to a destination.– e.g., air, twisted-pair cable, coaxial cable, fiber-optic
cable, conductor, and so on.
• Guided media– Provide a conduit from one device to another, include
twisted-pair cable, coaxial cable, and fiber-optic cable.
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Figure 7.2 Classes of transmission media
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7-1 GUIDED MEDIA7-1 GUIDED MEDIA
Guided media, which are those that provide a conduit Guided media, which are those that provide a conduit from one device to another, include twisted-pair cable, from one device to another, include twisted-pair cable, coaxial cable, and fiber-optic cable.coaxial cable, and fiber-optic cable.
Twisted-Pair CableCoaxial CableFiber-Optic Cable
Topics discussed in this section:Topics discussed in this section:
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Figure 7.3 Twisted-pair cable
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Figure 7.4 UTP and STP cables
Unshielded Twisted-Pair (UTP) Shielded Twisted-Pair (STP)
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Unshielded vs Shielded Twisted-Pair Cable
• Unshielded twisted-pair (UTP)• Shielded twisted-pair (STP)
– Has a metal foil or braided-mesh covering that encases each pair of insulated conductors.
• Category– Electronic Industries Association (EIA) has developed
standards to classify unshielded twisted-pair cable into seven categories. Table 7.1 shows these categories.
• Connectors– Most common UTP connector is RJ-45 (RJ stands for
registered jack).
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Table 7.1 Categories of unshielded twisted-pair cables
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Figure 7.5 UTP connector
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Figure 7.6 UTP performance
Gauge is a measure of the thickness of the wire.
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Figure 7.7 Coaxial cable
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Table 7.2 Categories of coaxial cables
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Figure 7.8 BNC connectors
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Figure 7.9 Coaxial cable performance
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Figure 7.10 Bending of light ray
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Figure 7.11 Optical fiber
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Figure 7.12 Propagation modes
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Figure 7.13 Modes
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Table 7.3 Fiber types
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Figure 7.14 Fiber construction
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Figure 7.15 Fiber-optic cable connectors
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Figure 7.16 Optical fiber performance
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7-2 UNGUIDED MEDIA: WIRELESS7-2 UNGUIDED MEDIA: WIRELESS
Unguided media transport electromagnetic waves Unguided media transport electromagnetic waves without using a physical conductor. This type of without using a physical conductor. This type of communication is often referred to as wireless communication is often referred to as wireless communication.communication.
Radio WavesMicrowavesInfrared
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Figure 7.17 Electromagnetic spectrum for wireless communication
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Figure 7.18 Propagation methods
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Table 7.4 Bands
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Figure 7.19 Wireless transmission waves
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Figure 7.20 Omnidirectional antenna
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Radio waves are used for multicast communications, such as radio and
television, and paging systems.
Note
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Figure 7.21 Unidirectional antennas
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Microwaves are used for unicast communication such as cellular telephones, satellite networks,
and wireless LANs.
Note
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Infrared signals can be used for short-range communication in a closed area
using line-of-sight propagation.
Note
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