The IEEE 802.11 family of standards which provides for Wireless Ethernet or (Wi-Fi) has evolved
over the years. This article explains the differences between 802.11a 802.11b 802.11g 802.11n and 802.11i.
802.11
The IEEE (Institute of Electrical and Electronics Engineers) released the first wireless specification, 802.11, in
1997. Unfortunately, with a maximum network bandwidth of only 2 Mbps, it was impractical for most purposes
and very little 802.11 product was ever manufactured.
802.11a
In 1999 IEEE released the 802.11a amendment to the original standard. 802.11a uses the same core protocol
as the original standard, but operates in 5 GHz band, and uses a frequency-division multiplexing scheme that
produces a maximum data rate of 54 Mbps. However, at the about same time 802.11a was created, the
802.11b specification was in development, and 802.11b signals are not absorbed as easily by walls and other
solid objects in their path.
802.11b
Later in 1999 released the 802.11b specification which operates in the 2.4 GHz band and produces a maximum
data rate of 11 Mbps. 2.4 GHz devices are much cheaper to produce and the signals can penetrate walls and
solid objects better than 802.11a, so 802.11b gained popularity much faster than did 802.11a. However,
because of it's higher bandwidth, 802.11a can be found in many business networks.
Because 802.11a and 802.11b use different frequencies, the two devices are incompatible with each other.
Some manufacturers produce devices that are compatible with both frequencies, but they actually have
circuits for both frequencies on the devices.
802.11g
In 2003 the 802.11g standard was released. It uses both the 2.4 GHz and 5 GHz band, uses the same
frequency-division multiplexing scheme as 802.11a, and produces a maximum data rate of 54 Mbps.
It has built-in backward compatibility with 802.11b and can achieve the speed of 802.11a. Because of
its higher speed the 802.11g standard is quickly gaining popularity.
802.11n
In 2009 the 802.11n standard was released. It improves the previous standards by adding multiple-input
multiple-output (MIMO) technology. MIMO uses multiple antennas to coherently resolve more information
than possible using a single antenna. It uses a multiplexing scheme called Spatial Division Multiplexing (SDM).
SDM multiplexes multiple independent 40 MHz data streams. A maximum data rate 600 Mbps is achieved
by multiplexing four 40 MHz streams.
802.11i
The security protocol used for all the 802.11 standards, Wired Equivalent Privacy (WEP), was shown to
have severe security weaknesses. The Wi-Fi Alliance has created the 802.11i specification to incorporate
a more robust security scheme called Wi-Fi Protected Access (WPA) which uses Advanced Encryption
Standard (AES) block cipher.
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