802.11a was launched in 2001 in a blaze of publicity, as a high speed alternative to 802.11b wireless LANs, operating in a different part of the radio spectrum. Then another group at the IEEE created the 802.11g standard, which offers a similar theoretical speed-boost, without changing frequency and with backward compatibility.

Intel's support for 802.11a wavered, and users started to sound uninterested. Vendors even started to suggest that maybe it would be one of those standards that has its purpose as a bit of future-proofing for users who want to hedge their bets but never actually gets used.

But now things are changing. Industry insiders are starting to get gung ho about it, arguing that 802.11a is a going condern, not a good idea that failed to happen. Meanwhile, users and analysts are starting to think that, maybe, its extra capacity could be what they need.

"I am noticing a sudden upsurge in .11a," says analyst Richard Webb of Infonetics Research. The research company does not publish separate figures for the two bands, but when vendors report them separately to Infonetics, the increase is significant, he says.

Faced with an array of network infrastructure needs and end-user demand, network executives are adding 802.11a technology to older WLANs, or deploying from scratch wireless networks that can support the 54 Mbit/s 802.11a and g and the older 11 Mbit/s 802.11b. (Read some case studies here).

At sites where these deployments are unfolding, users say 802.11a delivers two critical advantages:

  • It runs in the 5 GHz band, free of interference from the crowded 2.4 GHz band used by 802.11b and g (and microwave ovens and Bluetooth).
  • It offers 12 to 24 radio channels instead of 802.11b and g's three channels, so you can give far more throughput to many more users.

Building mixed WLANs has become easier over the past nine months as more enterprise-class access points and network interface cards (NICs) have come to market with radios that can transmit at 5 GHz for 802.11a and 2.4 GHz for 802.11b and g. Most of these are based on a dual-band chipset from Atheros. IDC says 802.11g radio chipsets for access points will account for 66 percent of the market this year and next, and dual-band 802.11a and b/g chipsets will jump from 11 percent this year to 22 percent in 2005.

More expensive - and you need more APs
Products that support 802.11a/b/g are more expensive than those for only 802.11g (which can throttle down to work with 802.11b clients). And you need two to four times as many 802.11a radios as 802.11b or g radios to cover a given space.

The 802.11a products are somewhat more expensive than 802.11g or b products. A recent review of online prices for enterprise-class access points found 802.11g-only products were priced from $240 to $610, and the combination 802.11a/b/g were priced from $490 to US$1,030.

User demand could rise significantly by next year when Intel begins promoting its delayed alternative to the Atheros Communications Inc. chipset. The company's dual-band Sonoma package for mobile computers, a follow-on to Centrino, recently delayed, will include the new Dothan Pentium M CPU and the Calexico 2 radio chipset. Calexico will be the first Intel chipset that can use either radio band and thus connect to 802.11a or b/g access points.

Growing pains
When 802.11a products emerged in 2001, "they experienced a boomlet and promptly died," says Abner Germanow, program manager for enterprise computing at IDC. Early products had range problems and were slower to fall in price than 802.11b and then 802.11g, he says.

Because 802.11b and then 802.11b/g WLAN deployments tended to be relatively small, enterprise users rarely ran into bandwidth problems, capacity issues or radio channel conflicts. With 802.11b, users share a data rate of 11 Mbit/s and actual throughput of 5 to 7 Mbit/s, depending on distance. The 11g networks, using the same modulation scheme as 802.11a, boost those numbers to 54 Mbit/s, or 20 to 25 Mbit/s actual throughput (why is actual throughput lower?).

But now network executives are extending their WLANs, more users are wireless, and applications are more demanding.

Much of this is driven by wireless voice over IP, according to Webb: "802.11a's shorter distances and higher capacity work out quite well for voice," he says. "You just won't be able to support voice over g or b."

We haven't seen that much voice over WLAN here yet. There's a doughnut warehouse using it, but most users we know are still keeping well clear.

However, even without VoIP, those WLAN infrastructures are being expected to carry more capacity, so they are being designed with both frequency bands in mind, and sometimes all three WLAN standards.

"We are seeing a/g deployments, more than a on its own," says Webb. We are seeing radios get swapped out and replaced, or users adding access points, so a b network becomes an a/b network." One common set-up is to use g for data and a for voice, he says.

A company can choose to overlay 802.11a on an 802.11b network or go with 802.11a/g for brand-new networks, says Philip Solis, a senior analyst with ABI Research. "They're future-proofing themselves," he says.

Want to meet real users of 802.11a? Read our companion article.