IEEE 802.11
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IEEE 802.11 is a standard for a wireless local area network (wlan). The standard is better known as Wi-Fi. The 802.11 standard comprises of a number of specifications.
The original 802.11 standard was published in 1997. This standard provided a data speed of 1 or 2 Mbit/s. The standard operates in the nearly worldwide available 2.4 GHz band ranging from 2400 - 2483.5 MHz. The standard uses either frequency hopping or coding (direct sequence spread spectrum) technology to make the transmissions robust.
802.11b
The standard became popular after the publication of a extension in 1999, called 802.11b. This extension to the original standard provides a maximum bit rate of 11 Mbit/s. The bit rate will be decreased to 5.5, 2 or 1 Mbit/s if the link quality decreases. The 802.11b standard uses direct sequence spread spectrum coding.
802.11g
The 802.11g standard was a further development of the standard to improve the bit rate if the link quality allows. The maximum bit rate is 54 Mbit/s. This bit rate can only be achieved if the user is in the vicinity of the access point.
802.11a and 802.11h
The 802.11a extension to 802.11 was developed to make use of the lower part of the 5 GHz band. The standard has a maximum bit rate of 54 Mbit/s using OFDM. The allocation in the 5 GHz band for RLAN was later extended. The 5 GHz band ranging from 5150-5350 and from 5470 - 5725 MHz can be used nowadays in most parts of the world. However, equipment has to detect and avoid radar systems that use the band and need to have transmit power control. The 802.11h standard was developed to cater for these provisions.
802.11n
IEEE 802.11n is a standard that further improves the data throughput. The throughput goal is at least 100 Mbit/s. This througput is achieved by using more than one channel (channel bonding) and advanced antenna technology (MIMO). Approval of the 802.11n standard is expected in 2007.
802.11n
IEEE 802.11r adds support for roaming to the standard. This makes seamless handovers possible in larger areas with WiFi coverage.
