Copyright © NDSL, Chang Gung University. Permission required for reproduction or display. Chapter 7...

Copyright © NDSL, Chang Gung University. Permission required for reproduction or display.

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: jhchen@mail.cgu.edu.twURL:

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

Topics discussed in this section:Topics discussed in this section:

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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