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LTE, WiMAX and WLAN Network Design, Optimization and Performance Analysis by Leonhard Korowajczuk

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Chapter 12

Wireless LAN

12.1 Standardization

The popularization of computers at home created the need to interconnect several devices, such as desktops, switches, laptops, printers, cable modems, and so on. WLAN (Wireless Local Area Network) became attractive as it did not require wires and gave mobility to laptops, but to be implemented it required the RF spectrum.

The RF spectrum is regulated by government agencies, requiring that users obtain licenses to use it. Industries, universities and radio amateurs were assigned unlicensed bands for use in laboratories and short range communications, as is the case of the ISM (Industrial, Scientific and Medical Equipment) bands and the U-NII (Unlicensed National Information Infrastructure) band. These bands were used in microwave ovens, car alarms, wireless phones and other similar devices. Over time, regulators conceded that these bands could also be used for short range broadband communications. ISM bands are listed in Table 12.1 and UNII bands in Table 12.2. UNII bands are subject to DFS (Dynamic Frequency Selection) because they are shared with radar operations and have to switch frequencies if a radar signal is detected.

Table 12.1 ISM band

ISM band as per ITU-R
Frequency (MHz)
From To Bandwidth
6.765 6.795 0.030
13.553 13.560 0.007
26.957 27.283 0.326
40.66 40.70 0.04
433.05 433.92 0.87
902 928 26
2400 2500 100
5725 5875 150
24,000 24,250 250
61,000 61,500 500
122,000 123,000 1000
244,000 246,000

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