802.11 is a series of IEEE specifications describing wireless data transfer. Most commonly implemented in WiFi applications, 802.11 has become the de-facto wireless connection specification for long-term connection and application function. Only Bluetooth currently competes with 802.11 for single file, non persistent data transfer between consumer electronic devices. However two other wireless specifications, WirelessUSB and WiFiMax, are under rapid development and new gadgets are being introduced that utilize these technologies.
802.11 is now one of the physical layer protocols adapted by TCP/IP, and includes the data link layer in it's specification. While in theory this reduced complexity by reducing the TCP/IP layer stack from five layers to four, in reality the data link layer is implemented in two sublayers. Therefore, 802.11 implementations have one additional layer effectively added to the stack, not one removed. Based on Ethernet protocol techniques and methods, 802.11 handles interference, packet loss, and error correction in a manner consistent with Part 15 of the FCC regulations for unlicensed use of the 2.4 and 5 GHz bands. 802.11, like all Part 15 compliant standards, gives frequency priority to licensed operators and causes them no interference. Additionally, the specification is designed to accept interference from non-malicious licensed users of the band.
Notable among the 802.11 revisions are revisions 'a', 'b', and 'g'. Each form the basis for different, incompatible WiFi implementations designated by the same letter as the 802.11 revision they are based upon. The first to find widespread use was 802.11b, as it was very similar to the original 802.11 draft specs. Introduced in October 1999, the 'b' specification operates in the popular 2.4 GHz band and provides up to 1.5 MB/sec (11 Mbit/sec) of bandwidth. Although ratified slightly before the 'b' specification, the 'a' specification took longer to adapt as it operates in the less popular 5 GHz band. The high frequency ensures an interference-free transmission, however the short wavelength cannot adequately penetrate common building materials such as steel and concrete. Thus, 802.11a was an unsuitable standard for indoor use despite providing up to 7 MB/sec (54 Mbit/sec) data transfer rate. Three years after the introduction of 802.11a and 802.11b, 802.11g was introduced. This new specification achieves it's 7 MB/sec (54 Mbit/sec) speed in the 2.4 GHz band through OFDM modulation. However, the crowded 2.4 GHz band often severely limits the range of high-speed 802.11g access, and the presence of a compatible 802.11b device on the network brings speeds down to the 'b' specification's maximum.
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