The Many Flavors of 802.11

The 802.11 standard is defined through several specifications of
WLANs. It defines an over-the-air interface between a wireless client
and a base station or between two wireless clients (Figure 1.3).
There are several specifications in the 802.11 family:


802.11—Pertains to wireless LANs and provides 1- or 2-Mbps transmission
in the 2.4-GHz band using either frequency-hopping spread
spectrum (FHSS) or direct-sequence spread spectrum (DSSS).


802.11a—An extension to 802.11 that pertains to wireless LANs and
goes as fast as 54 Mbps in the 5-GHz band. 802.11a employs the
orthogonal frequency division multiplexing (OFDM) encoding scheme
as opposed to either FHSS or DSSS.


802.11b—The 802.11 high rate Wi-Fi is an extension to 802.11 that
pertains to wireless LANs and yields a connection as fast as 11 Mbps
transmission (with a fallback to 5.5, 2, and 1 Mbps depending on
strength of signal) in the 2.4-GHz band. The 802.11b specification
uses only DSSS. Note that 802.11b was actually an amendment to the
original 802.11 standard added in 1999 to permit wireless functionality
to be analogous to hard-wired Ethernet connections.


802.11g—Pertains to wireless LANs and provides 20+ Mbps in the
2.4-GHz band.