Expanded, WiMax means World wide Interoperability for Microwave Access.

And who would be the beneficiaries? Well, proponents of the technology claim that it will make broadband affordable to masses, though the initial adopters would be enterprises, as usual.

Theoretically, all of the above are correct. Practically too, encouraging results have been reported from ongoing trials, some of which are being run in India as well.

What's New about It?
There is nothing new about WiMax, as a concept. Wi-Fi uses much the same concept, as do some other microwave technologies like MMDS. Both the technologies use orthogonal frequency division multiplexing (OFDM) or its variants.

In fact, WiMax is more of a standard than a technology. A key purpose that the standard serves is to focus much of the microwave access work to a more manageable frequency range.

Earlier, vendors were developing products for too wide a spectrum-from 2 GHz to 66 GHz. That made it too scattered and hence less appealing for carriers. The WiMax standard put a tab on the upper range, at 11 GHz.

Typically, the sub-11 GHz bands are characteristically more suited for non–line of sight (NLOS), last-mile distribution, whereas the higher frequencies (up to 66 GHz) adapt well for LOS backhauling.

It is therefore that WiMax, as a last-mile wireless broadband technology, sought to use the 2 GHz to 11 GHz frequencies.

Spectrum Availability
Not the entire range is available globally. Let's look at what all bands are usable and promising for WiMax growth.

Two license-exempt industrial, scientific, and medical (ISM) bands exist between 2.4–2.48 GHz and 5.73–5.85 GHz frequencies. Another unlicensed band exists between 5.15–5.85 GHz (one may note the overlap with the upper ISM band here) and is referred to as the Unlicensed National Information Infrastructure (U-NII) band.

Then there is the multi-channel multipoint distribution service (MMDS) band in the 2.5–2.7 GHz range. This channel was originally earmarked for instructional TV purposes in the US, but has now been licensed to Sprint, Worldcom, and Nucentrix. More than 30 channels of 6 MHz each exist in this band there.

Licensed channels in the 3.3–3.6 GHz band are available in many Asian and European countries for broadband wireless access (BWA) purposes. In India the proposed range is 3.3–3.4 GHz.

It is in this light that WiMax Forum had identified three frequency bands-namely 2.4 GHz, 3.5 GHz, and 5.8-for harmonization works.

WiMax stakeholders have also been lobbying with governments world over to free up the 700–800 MHz frequencies for wireless broadband usage.

As of now, most of the WiMax gears are in the pre-certification stage-WiMax Forum will begin certifying products only in mid-2005. Also, bulk of the development is for frequencies between 2 GHz and 11 GHz.

WiMax versus Wi-Fi
An initial apprehension, of Wi-Fi interest groups, was that WiMax will be a threat to Wi-Fi in future, especially because it would use the same frequencies and have a longer range, both in LOS and NLOS conditions.

WiMax advocates sought to clear the fear by assuring that the technology would complement rather than cannibalize Wi-Fi. The argument was that while Wi-Fi had a role to play as a wireless LAN technology, WiMax would serve as wireless MAN technology.