802.11

Developed as a standard by the Institute of Electrical and Electronic Engineers (IEEE,
or I-triple-E), 802.11 is a radio technology used for wireless local area networks (WLANs). 802.11 is the parent standard of several technologies operating across several different frequencies.The 802.11 specification defines three types of wireless LAN, all operating at a
data transmission rate of 1Mbps or 2Mbps. 802.11 FHSS and 802.11 DSSS use radio frequency radiation as the transmission medium. The third 802.11 specification is based on diffuse infra-red transmission.

802.11a

Operates in the UNII (Unlicensed National Information Infrastructure) 5GHz band with a maximum data transfer rate of 54 Mbps.. 802.11a uses Orthogonal Frequency Division Multiplexing (OFDM), as opposed to the DSSS or FHSS schemes used in 802.11b and
802.11 networks. Due to its higher frequency of operation, the range of 802.11a equipment is less that of lower frequency systems such as 802.11b and 802.11g. This can increase the cost of an 802.11a network, because a greater number of access points may be required. Since it operates in a different RF band, 802.11a cannot work directly with 802.11b or 802.11g equipment. Using multi-mode 802.11a/b/g access points and/or client adapters will resolve this problem.

802.11b

Currently the most popular and widespread standard for wireless LANs, which operates in the 2.4GHz ISM band and supports data rates up to 11Mbps. Also known as 802.11 High-Rate (HR) and as Wi-Fi, 802.11b uses the DSSS spread spectrum transmission scheme, and operates at
data rates of 1Mbps, 2Mbps, 5.5Mbps and 11Mbps.