Operating Channels
Wi-Fi uses a segment of the radio spectrum (also called a band) near 2.4 GHz that has been reserved for unlicensed industrial, scientific, and medical (ISM) services, including wireless data networks. 802.11b, 802.11g, and 802.11n all use this band of frequencies. 802.11a uses a different frequency band near 5.2 GHz known as the Unlicensed National Information Infrastructure (U-NII).
Both the ISM and U-NII bands are open to many kinds of unlicensed radio services. This means that the people who make the equipment must demonstrate that their designs meet various regulations related to maximum power, interference, and so forth, but actual users (that's you and me) don't need to obtain licenses before they can operate approved radios. ...
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