Page 192 - Computer_Science_F5

Unguided/wireless transmission media
In unguided transmission, data travels in the air in the form of electromagnetic waves
enabled by antennas. The antennas are used to transmit and receive signals between
the source and destination. Unguided media are also known as wireless media. Chapter Three: Advanced Computer Networks
Examples of unguided media are wireless transmission such, as radio, microwave,
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infrared, and sound. Unguided media, also called wireless communication, transmits
electromagnetic waves without using a physical medium. Unguided media use an
antenna for transmitting through air, vacuum, or water. Unguided media information
travels in the form of electromagnetic signals through the air. The electromagnetic
spectrum of frequency ranges from 3 kHz to 900 THz; this range is available for
wireless communication as shown in Figure 3.37.

3 1 300 400 900
KHz GHz GHz THz THz

Radiowaves Microwaves Infrared Light waves
waves

Figure 3.37: Electromagnetic waves spectrum

Wireless technologies allow the transmitter and receiver do not have
communication between two or more to be carefully aligned physically,
devices from short to long distances
without any physical media. There Microwave transmission: In microwave
are many wireless communication transmission, the waves travel in straight
technologies, such as Bluetooth, Wi- lines. It gives a much higher signal-noise
ratio, but the transmitting and receiving
Fi, and WiMAX. The electromagnetic antennas must be accurately aligned with
spectrum ranges from 3 kHz to 900 THz. each other,
It can be divided into four categories
according to their frequency ranges, as Infrared waves: Infrared waves are widely
shown in Figure 3.37. These are Radio used for short-range communication. The
waves, Microwaves, Infrared waves, and remote controls used on television, Video
Light waves. Cassette Recordings (VCRs) and stereos
use infrared communication,
Radio waves: Radio waves can be
broadcast in all directions from the Communication satellite: In satellite
source, that is, omnidirectional so that communication, signal transferring

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Student’s Book Form Five

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