Wireless Standards 802.11a, 802.11bgn, and 802.11ac

Wireless Standards 802.11a, 802.11b/g/n, and 802.11ac
1- 802.11
In 1997, the Institute of Electrical and Electronics Engineers (IEEE) created the first WLAN
standard. They called it 802.11 after the name of the group formed to oversee its development.
Unfortunately, 802.11 only supported a maximum network bandwidth of 2 Mbps - too slow for
most applications. For this reason, ordinary 802.11 wireless products are no longer
manufactured.
2- 802.11b
IEEE expanded on the original 802.11 standard in July 1999, creating the 802.11b specification.
802.11b supports bandwidth up to 11 Mbps, comparable to traditional Ethernet.
802.11b uses the same unregulated radio signaling frequency (2.4 GHz) as the original 802.11
standard. Vendors often prefer using these frequencies to lower their production costs. Being
unregulated, 802.11b gear can incur interference from microwave ovens, cordless phones, and
other appliances using the same 2.4 GHz range. However, by installing 802.11b gear a
reasonable distance from other appliances, interference can easily be avoided.
3- 802.11a
While 802.11b was in development, IEEE created a second extension to the original 802.11
standard called 802.11a. Because 802.11b gained in popularity much faster than did 802.11a,
some folks believe that 802.11a was created after 802.11b. In fact, 802.11a was created at the
same time. Due to its higher cost, 802.11a is usually found on business networks whereas
802.11b better serves the home market.
802.11a supports bandwidth up to 54 Mbps and signals in a regulated frequency spectrum around
5 GHz. This higher frequency compared to 802.11b shortens the range of 802.11a networks. The
higher frequency also means 802.11a signals have more difficulty penetrating walls and other
obstructions.
Because 802.11a and 802.11b utilize different frequencies, the two technologies are incompatible
with each other. Some vendors offer hybrid 802.11a/b network gear, but these products merely
implement the two standards side by side (each connected devices must use one or the other).
4- 802.11g
In 2002 and 2003, WLAN products supporting a newer standard called 802.11g emerged on the
market. 802.11g attempts to combine the best of both 802.11a and 802.11b. 802.11g supports
bandwidth up to 54 Mbps, and it uses the 2.4 Ghz frequency for greater range. 802.11g is
backwards compatible with 802.11b, meaning that 802.11g access points will work with 802.11b
wireless network adapters and vice versa.
5- 802.11n
802.11n (also sometimes known as "Wireless N") was designed to improve on 802.11g in the
amount of bandwidth supported by utilizing multiple wireless signals and antennas (called
MIMO technology) instead of one. Industry standards groups ratified 802.11n in 2009 with
specifications providing for up to 300 Mbps of network bandwidth. 802.11n also offers
somewhat better range over earlier Wi-Fi standards due to its increased signal intensity, and it is
backward-compatible with 802.11b/g gear.
6- 802.11ac
The newest generation of Wi-Fi signaling in popular use, 802.11ac utilizes dual band wireless
technology, supporting simultaneous connections on both the 2.4 GHz and 5 GHz Wi-Fi bands.
802.11ac offers backward compatibility to 802.11b/g/n and bandwidth rated up to 1300 Mbps on
the 5 GHz band plus up to 450 Mbps on 2.4 GHz.
http://compnetworking.about.com/cs/wireless80211/a/aa80211standard.htm