802.11 is the wireless standard (Wi-Fi) established by the IEEE (Institute of Electrical and Electronics Engineers). There are three types of common Wi-Fi technology in use today, and research and development continuously improves both bit rate and range.
802.11a
Operates in the 5 GHz spectrum, at speeds up to 54 Mbits/s. 802.11a was adopted by corporations specifically because of its better ability to use fewer access points for more users and speed boost was also a factor. Another factor that helped high-end technology adopt the standard was the use of the 5Ghz spectrum, which does not trip over other devices. 802.11a equipment carried an additional price increase, perhaps because of economies of scale. It also suffers from a shorter range then the 802.11b standard.
802.11b
uses the 2.4 Ghz spectrum. rates range 1 to 11 Mbits/s dependent on range and interference.. Sometimes interference is incurred by other devices in consumer environments. This was the first widely available consumer level wireless technology. Enhanced versions use techniques such as channel bonding and burst transmission to increase rates, but these are not part of the official standard – interoperability between vendors may suffer.
802.11g
2.4-GHz radio spectrum. Transfer for 11g is rated up to 54 Mbits/s. 802.11g is the current consumer level choice because of availability, compatibility with existing 802.11b equipment and price. The range at which 802.11g equipment can maintain its highest speeds is smaller then 802.11b.
When 802.11g and 802.11b clients share a network, 802.11g clients suffer because the two standards use different types of modulation. 802.11g clients use the same type of modulation as 802.11a clients, OFDM (Orthogonal Frequency Divison) Multiplexing. OFDM Breaks data into subsignals and transmits them simultaneously across different frequencies. 802.11b clients use DSSS Direct Sequence Spread Spectrum multiplexing. Direct Sequence Spread Spectrum sends a seperate high speed transmission containg the data in addition to the data- this allows reconstruction in case of a disruption.
802.11n
Pre-n technology is available now, but is not based on a shared ratified standard. Speeds are in the neighborhood of 100 to 540 Mbits/s. Early adopters may pay the price with incompatible hardware once a standard is ratified. The Pre-n is not limited to using the 2.4Ghz range, but commonly does for cost considerations. This technology typically uses a multiple path scheme called MIMO (Multiple In Multiple Out) to increase available bandwidth between clients and an access point. Some Pre-n equipment interferes with other wireless gear, rendering it inoperable in the Pre-n unit’s range. New implementations of 802.11n gear are becoming widely available, with Apple shipping n cards disabled in software in their newest products.