This section briefly describes the variants of the 802.11 standard.
It's perfectly possible for a wireless chip to run multiple flavors of 802.11. For example, one of the chipsets available to laptops using Intel Centrino mobile technology runs 802.11b, 802.11g, and 802.11a. This "three-way" Wi-Fi radio will choose the most appropriate 802.11 variant depending on the network it is connecting to and the preferences of the user.
Many Wi-Fi devices currently in operation are using the 802.11b flavor of 802.11 (although the backward compatible and faster 802.11g has replaced 802.11b as the reigning "monarch" of Wi-Fi).
The full 802.11b specification document is more than 500 pages long, but the most important things to know about 802.11b are that
An 11Mbps speed isn't bad. However, for a variety of reasons, Wi-Fi connections rarely achieve anything close to 11Mbps. Over an encrypted 802.11b connection, you'll be lucky to get transmission rates of more than 6Mbps. This is certainly fast enough for transferring Word documents, but probably not fast enough for applications such as streaming video.
If you go out today and buy a wireless laptop, or a wireless access point, it is most likely to use 802.11g. Like 802.11b, 802.11g runs on the 2.4GHz spectrum. One of the best things about 802.11g is that it is fully backward compatible with 802.11b. If your Wi-Fi laptop is equipped with 802.11b, you can connect to an 802.11g hotspot, although of course you will only achieve 802.11b throughput. (There are also some questions about whether placing 802.11b devices on an 802.11g network will degrade the entire network, not just the 802.11b portions of it, although this problem has mostly been resolved.)
Conversely, an 802.11g-equipped computer can connect to an 802.11b access point, once again at the lower speeds of 802.11b.
By comparison to 802.11b, 802.11g is blazingly fast, achieving throughput in the best conditions of 54Mbps. (Real-world actual rates tend to be around 25MBps.) This is still a little slower than a sophisticated 100Mbps wired Ethernet network but quite fast enough for most applications including streaming video and music. (Video and music streaming quality depends on many factors, such as lost packet rate, not just raw throughput.)
Unlike either 802.11b or 802.11g, 802.11a operates on the 5GHz spectrum. That's good news from the viewpoint of interference. There's simply less going on in the 5GHz band, and you are less likely to "bump into" other Wi-Fi networks, garage door openers, cordless phones, or whatnot. However, it is bad news from the point of backward compatibility because 802.11a systems are not compatible with 802.11b (or 802.11g) because they use a different spectrum.
As I noted earlier, some vendors have solved this problem by creating tri-mode chipsets that run 802.11a, 802.11b, and 802.11g depending on the access point or hotspot they are connecting to. If you are considering purchasing an 802.11a Wi-Fi device, make sure that it has this kind of standard switching capability.
You can expect a throughput of something like 20Mbps with 802.a, so from a speed viewpoint, it is faster than 802.11b and pretty comparable 802.11g.
Generally speaking, you'd buy a Wi-Fi computer that only uses 802.11a if you are using it on a dedicated 802.11a networkfor example, run by your companyand don't plan to take it anywhere else. However, the safest thing to do is to buy a trimode Wi-Fi computer that works with all three standards.
802.11n is a developing standard not yet approved by the IEEE that promises to deliver greater than 100 Mbps (and perhaps as fast as 500Mbps) using both the 2.4GHz and the 5GHz spectrums. Despite the fact that the official standards approval process is not complete, some companies, such as Belkin and Broadcom, are likely to jump the gun and start producing "pre-standards approval" 802.11n chipsets and devices shortly.
Complicating matters, at the time of this writing, there are two different 802.11n camps, with different ideas about what the 802.11n standard should be when it is finalized.
Still, in the due fullness of time, and when the dust settles, no doubt a workable 802.11n Wi-Fi standard will emerge. In effect, 802.11n is part of a process of better technology becoming more affordable. Right now, 802.11b is downright cheap. Equipment made using the 802.11g standard is faster, and on the marketbut a bit more expensive. It won't be long before 802.11g is inexpensive, with new, faster (but higher priced) 802.11n equipment coming on the market. Further down the time horizon, we can expect the same process to be repeated with 802.16, commonly known as WiMAX.
802.11i is the name given by the IEEE to its security standard. This standard is virtually the same as the "Wi-Fi Protected Access," or WPA2, the version adopted by the Wi-Fi Alliance.