Wireless network. What Is a wireless network? Types of wireless networks: Performance of wireless networks (Understanding wireless networks) by Tim N Towen

Author:Tim N Towen
Language: eng
Format: azw3, pdf
Published: 2017-07-08T07:00:00+00:00

1.3 The electromagnetic spectrum

Characteristics of wireless communication link - distance between nodes, coverage area, information rate, etc. -.. Largely depend on the used frequency of the electromagnetic spectrum (frequency f and wavelength X related by x = f X).

The ranges of the electromagnetic spectrum are shown in Figure B.2 in Appendix B. It is possible to say that they and their corresponding wireless data transmission systems are divided into four groups.

□ Range up to 300 GHz has a common standard name - radio range . Union ITU divided into several sub-bands (and is shown in the figure), from ultra-low frequency (Extremely Low Frequency, ELF) and ultra-high finishing (Extra High Frequency, EHF). Familiar to us radios operate in the range of 20 kHz to 300 MHz, and for these bands there but not defined in the standards, but chaete) used the name of the radio broadcast . These systems fall into low speed AM- and FM-bands for transmitting data at speeds of several tens to hundreds of kilobits per second. Examples are the radios that connect the two LAN segment at speeds of 2400, 9600 or 19200 kbit / s.

□ Several bands from 300 MHz to 3000 GHz are also non-standard name of the connection in the microwave range. Communication microwave uses high frequency and is used as a short range and a global scale. Microwave systems represent the most broad class of systems, combining microwave link, satellite TV, wireless LAN and fixed wireless access system ,, also called wireless subscriber terminations systems (Wireless Local Loop, WLL).

□ Above the microwave range is the infrared range. Microwave and infrared ranges are also widely used for wireless transmission of information. Since the infrared radiation can not penetrate through the walls, the system of infrared waves are used for the formation of small segments of LANs within the same room.

□ In recent years, visible light also began to be used for transmission of information (using lasers). Visible light systems are used as high-speed alternative to the two-point microwave channels to provide access over short distances.

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