This section briefly describes the variants of the 802.11 standard.
Most Wi-Fi devices that are currently in operation are using the 802.11b flavor of 802.11 (although both 802.11a and 802.11g are up and coming).
The full 802.11b specification document is more than 500 pages long, but the most important things to know about 802.11b are that
802.11b uses the 2.4GHz spectrum.
802.11b has a theoretical throughput speed of 11 Megabytes per second (Mbps).
A speed of 11Mbps isn't bad (by comparison, a normal, wired Ethernet network only gets 10Mbps). However, for a variety of reasons Wi-Fi connections rarely achieve anything close to 11Mbps. You'll be lucky over an encrypted 802.11b connection to get transmission rates of over 6Mbps. This is fast enough for transferring Word documents, but probably not fast enough for applications such as streaming video.
A newer version of 802.11, 802.11g, like 802.11b 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 802.11 throughput. 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. This is still slower than a sophisticated 100MBps wired Ethernet network, although a good bit faster than the 10MBps equipment used in most home networks.
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 what not. 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.
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. It's a good idea if you are considering purchasing an 802.11a Wi-Fi device to make sure 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 midway between 802.11b and 802.11g.
802.11n is a developing standard that has not yet been approved but promises to deliver greater than 100Mbps using both the 2.4GHz and the 5GHz spectrums. Despite the fact that the official standards approval process is likely to take several years, it seems likely that some companies, such as Broadcom Corporation, are likely to jump the gun and start producing "pre-standards approval" 802.11n chipsets and devices shortly.
This may in turn cause the IEEE to speed its approval of a new 802.11n standard. In effect, 802.11n is part of a process of better technology becoming more affordable. Right now, 802.11b is inexpensive. Equipment made using the 802.11g standard is faster, and on the market?but more expensive. It won't be all that long before 802.11g is inexpensive and what everyone is buying, with new, faster (but higher-priced) 802.11n equipment coming on the market.
802.11i is the name given by the Wi-Fi Alliance to its proposed new security standard.
Products that successfully complete the test required for meeting the 802.11i standard will be called "Wi-Fi Protected Access" certified.
For more information about Wi-Fi and network security, see Part V, "Securing Your Wi-Fi Computer and Network."