WiMax is the popular name of the 802.16 wireless metropolitan-area network standard that's currently being developed. WiMax, which will have a range of up to 31 miles, compared with Wi-Fi's 300 feet and Bluetooth's 30 feet. [for which read 10 miles, 100 feet and 10 feet - Ian]
The popularity of wireless networking has grown very quickly because of effective standardization. Wi-Fi encompasses a family of specifications within the IEEE 802.11 standard. These include 802.11b (the most popular, at 11Mbit/sec., with a typical range of up to 300 feet), 802.11a (54Mbit/sec., but at a shorter range than 802.11b) and 802.11g (combining the speed of "a" with the range of "b").
WiMax is the new shorthand term for IEEE Standard 802.16, also known as "Air Interface for Fixed Broadband Wireless Access Systems." It's been designed from the beginning to be compatible with European standards, something that didn't happen with 802.11a and delayed its adoption.
Intel has now promised WiMax versions of its Centrino chip set for 2004, whereas Nokia says it will have battery and other technical issues solved in time to launch a WiMax cell phone in 2005.
Following on the heels of WiMax is another standard, IEEE 802.20, which addresses wide-area wireless networks and is currently under development; no products supporting 802.20 are expected before 2006.
The new broadband wireless specs are known by numbers matching their specific IEEE working groups. The first, 802.16, is for metro fixed-point wireless, and will compete against DSL, cable, and dial-up for homes and businesses. The second, 802.20, is for wireless data services for mobile users, and could compete with cellular, 3G, and other similar services.