The IEEE 802.16 standard, better known as WiMax, is a wireless metropolitan area network technology with a theoretical data throughput of about 75Mbit/s across a distance of about 30 miles, operating mainly at 2.4, 3.5 and 5.8GHz. The current standard, 802.16-2004 for fixed wireless access, was ratified last year. Its major uses are to aggregate Wi-Fi hotspots or to extend or replace cable and digital subscriber line (DSL) technologies for last-mile access.

A report from analyst firm Gartner at the end of last year predicted that the most important applications for WiMax in metropolitan areas will be to extend the reach of DSL and to support mobile broadband. In the longer term, Gartner predicts mobile broadband will be the main focus, and will account for nearly half of WiMax equipment revenue and connections in 2009.

Trials are being conducted for the National Museum of Science and Technology (NMSI) by Alvarion and Intel at Wroughton, an ex-Royal Navy airfield near Intel's UK headquarters in Swindon. The NMSI's pre-802.16-2004 WiMax system aggregates Wi-Fi links for 11 aircraft hangars. Some may see the trial as an ideal scenario, since the location has few obstructions and little electromagnetic interference. Crowded city centres will present a more demanding test for WiMax.

Since WiMax's main use will be for mobile wireless broadband, there are many hurdles before it can take off. Gartner highlights the key developments as ratification of the 802.16e standard, expected in the third quarter; the availability of 802.16e chipsets in late 2006; the success of the South Korean experiment with WiMax-derivative Wireless Broadband, "WiBro"; and integ- ration of WiMax in PCs in 2009.

Gartner analyst Ian Keene said that if the deadlines slip, WiMax might be only "moderately" successful rather than very successful. Keene is optimistic about the technology's prospects, however, and said the backing of Intel and WiMax's flexibility are encouraging signs. Keene also predicted that 3G will not be a major rival to WiMax, because voice on 3G will take up too much bandwidth.

The developers of WiMax have learned from problems encountered with Wi-Fi. WiMax has quality of service (QoS) built in and allows differentiated service levels for both business and residential users. "With WiMax, rather than just having the bare radio platform and not much else, the management is already in there," said Andrew Greenhaugh, Intel's mobile computing marketing director for Europe.

In the UK, available licence-exempt frequencies are 2.4GHz and 5.8GHz bands "a" and "b".

Band "c" is also available but registration is required to ensure there is no conflict with military transmissions. There is also licensed 3.5GHz spectrum owned by UK Broadband, a subsidiary of Hong Kong telecoms firm PCCW. The licence currently allows only fixed wireless access and not the 802.16e mobile version of WiMax, though Ofcom is reviewing this restriction.