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Chapter 7

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Transmission Media

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Figure 7.1 Transmission medium and physical layer

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Figure 7.2 Classes of transmission media

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7-1 GUIDED MEDIA

Guided media, which are those that provide a conduit from one device to another, include twisted-pair cable, coaxial cable, and fiber-optic cable.

Twisted-Pair Cable�Coaxial Cable�Fiber-Optic Cable

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

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Table 7.1 Categories of unshielded twisted-pair cables

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Figure 7.5 UTP connector

https://youtu.be/NWhoJp8UQpo

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Figure 7.6 UTP performance

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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

BNC connectors (Bayonet Neill-Concelman)

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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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7-2 UNGUIDED MEDIA: WIRELESS

Unguided media transport electromagnetic waves without using a physical conductor. This type of communication is often referred to as wireless communication.

Radio Waves

Microwaves

Infrared

Topics discussed in this section:

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Figure 7.17 Electromagnetic spectrum for wireless communication

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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.

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Figure 7.21 Unidirectional antennas

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Figure 7.12 Propagation modes

1. Ground Wave Propagation

• Waves travel along the surface of the Earth.
• Effective for low and medium frequencies (up to ~2 MHz).
• Used in AM radio broadcasting and maritime communication.

2. Sky Wave Propagation

• Waves are reflected by the ionosphere back to Earth.
• Suitable for shortwave frequencies (2–30 MHz).�Enables long-distance communication beyond the horizon.�

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3. Line-of-Sight (LOS) Propagation

• Waves travel directly from transmitter to receiver.
• Requires clear, unobstructed path.
• Used in TV broadcasting, FM radio, microwave, satellite, and mobile communication.�

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Figure 7.18 Propagation methods

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�Microwaves are used for unicast communication such as cellular telephones, satellite networks,�and wireless LANs.

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�Infrared signals can be used for short-range communication in a closed area using line-of-sight propagation.

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Transmission Media

Transmission media is the path through which data travels from sender to receiver. It is classified into Guided and Unguided media.

1. Guided Media (Wired)

Data signals travel through a physical medium.

• Twisted Pair: Two insulated copper wires twisted together; low cost, used in telephone lines and LANs.
• Coaxial Cable: Central copper conductor with shielding; better noise immunity, used in cable TV and broadband.
• Fiber Optic Cable: Uses light signals through glass/plastic fiber; very high bandwidth, long distance, and immune to electromagnetic interference.

2. Unguided Media (Wireless)

Data signals travel through air or space.

• Radio Waves: Omnidirectional; used in radio broadcasting and Wi-Fi.
• Microwaves: Directional; used in satellite and cellular communication.
• Infrared: Short-range, line-of-sight; used in remote controls and short-distance communication.

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