Field Guide to Wireless LANs for Administrators and Power Users, A

Overview of IEEE 802.11 PHYs

There are a remarkable number of Physical layer choices that may be used in the context of IEEE 802.11 WLANs. The large number of choices arises because there are a number of different physical media over which the frames can be transmitted, including diffuse infrared optical, as well as several different radio frequency bands, including a set of channels in the 2.4 GHz unlicensed ISM^[2] band (2.450 ± 0.050 GHz, which is a total RF bandwidth of 100 MHz), as well as several other unlicensed bands in the neighborhood of 5 GHz, for whom usability depends on the regulatory domain (i.e., country or geographical region) in which the product is being used.

^[2] There are numerous unlicensed Industrial, Scientific, and Medical ...