IEEE 802.11

IEEE 802.11
In June 1997, the IEEE finalized the initial standard for wireless LANs: IEEE 802.11. This
standard specifies a 2.4GHz operating frequency with data rates of 1Mbps and 2Mbps. The initial
802.11 standard defines two forms of spread spectrum modulation: frequency hopping
(802.11 FHSS) and direct sequence (802.11 DSSS).
In late 1999, the IEEE published two supplements to the 802.11 standard: 802.11a and
802.11b. IEEE 802.11b is a data rate extension of the initial 802.11 DSSS, providing operation
in the 2.4GHz band at up to 11Mbps. Most wireless LANs implemented today comply with the
802.11b version of the standard.
The 802.11a standard defines operation at up to 54Mbps using orthogonal frequency division
multiplexing (OFDM) modulation in the roomy 5GHz frequency band. The 802.11a standard
has a wide variety of high-speed data rates available: 6, 9, 12, 18, 24, 36, 48, and 54Mbps; it is
mandatory for all products to have 6Mbps, 12Mbps, and 24Mbps rates. Products implementing
the 802.11a standard should begin appearing on the market in late 2001.