QuickStudy: WiMax

Computerworld - Since the turn of the millennium, wireless networks have proliferated. Wi-Fi, the popular term for the capabilities created by a group of standards from the Institute of Electrical and Electronics Engineers Inc., has freed us to move around our offices and many public places with our laptops and handhelds, yet still have instant, unencumbered access to our companies' intranets and the Internet.

WiMax (Worldwide Interoperability for Microwave Access) is the next step on the road to a wireless world, extending broadband wireless access to new locations and over longer distances, as well as significantly reducing the cost of bringing broadband to new areas.

802.What?

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.

The nonprofit WiMax Forum was established in 2001 by Nokia Corp., Ensemble Communications Inc. and the Orthogonal Frequency Division Multiplexing Forum.

The WiMax Forum aims to support wireless metropolitan-area networking products based on 802.16, much as the Wi-Fi Alliance has done for wireless LANs and 802.11.

The organization has most recently been working on standards certification and interoperability testing. In 2003, Intel Corp. became a major supporter of the WiMax Forum.

The initial version of the 802.16 standard, approved by the New York-based IEEE in 2002, operates in the 10-to-66-GHz frequency band and requires line-of-sight towers.

The 802.16a extension, ratified in March 2003, doesn't require line-of-sight transmission and allows use of lower frequencies (2 to 11 GHz), many of which are unregulated. It boasts a 31-mile range and 70Mbit/sec. data transfer rates that can support thousands of users.

Vendors have held interoperability forums, and the first commercial products are expected to appear on the market next year.

Additional 802.16 standards are in the works; here's what they'll cover:

802.16b—Quality of service

802.16c—Interoperability, with protocols and test-suite structures

802.16d—Fixing things not covered by 802.11c, which is the standard for developing access points

802.16e—Support for mobile as well as fixed broadband