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EMERGING TECHNOLOGY WIMAX: A Whiff of Speed

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VoicenData Bureau
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Expanded, WiMax means World wide Interoperability for Microwave Access.

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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.

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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.

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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.

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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.

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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.

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