WLAN: Wireless LAN by IEEE 802.11, 802.11a, 802.11b, 802.11g

The Wireless Local Area Network (WLAN) technology is defined by the IEEE 802.11 wireless network family of specifications. There are currently four specifications in the wireless network family: 802.11, 802.11a, 802.11b, and 802.11g. All four use the Ethernet protocol and CSMA/CA (carrier sense multiple access with collision avoidance instead of CSMA/CD) for path sharing.

• 802.11 -- applies to wireless networks 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 applies to wireless networks and provides up to 54 Mbps in the 5GHz band. 802.11a uses an orthogonal frequency division multiplexing (OFDM) encoding scheme rather than FHSS or DSSS. The 802.11a specification applies to wireless ATM systems and is used in access hubs.
• 802.11b (also referred to as 802.11 High Rate or Wi-Fi) -- an extension to 802.11 that applies to wireless LANS and provides 11 Mbps transmission (with a fallback to 5.5, 2 and 1 Mbps) in the 2.4 GHz band. 802.11b uses only DSSS. 802.11b was a ratification to the original 802.11 standard, allowing wireless functionality comparable to Ethernet.
• 802.11g -- offers wireless transmission over relatively short distances at 20 - 54 Mbps in the 2.4 GHz band. The 802.11g also uses the OFDM encoding scheme.

The modulation used in 802.11 has historically been phase-shift keying (PSK). The modulation method selected for 802.11b is known as complementary code keying (CCK), which allows higher data speeds and is less susceptible to multipath-propagation interference. 802.11a uses a modulation scheme known as orthogonal frequency-division multiplexing (OFDM) that makes possible data speeds as high as 54 Mbps on wireless networks, but most commonly, communications takes place at 6 Mbps, 12 Mbps, or 24 Mbps.

To learn more about wireless protocols, click here.