Proposal could ease wireless upgrades

An upcoming IEEE vote could simplify enterprise deployment of wireless LANs . . . or confuse things still further.

A task group of the IEEE is scheduled to vote this month on adopting a proposal by wireless chip maker Intersil that would let future wireless LAN products, such as interface cards and access points, support wireless LANs operating in either of two different radio frequencies: 2.4 GHz and 5 GHz.

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A wireless LAN migration path?

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Such a "dual-band radio" would let a laptop user tap into one of today's IEEE 802.11b LANs, which run up to 11M bit/sec, on 2.4 GHz. But it also would let the same user make use of either 802.11g nets, which will run over 20M bit/sec on the same 2.4-GHz band, or the upcoming 802.11a LANs, which run up to 54M bit/sec on the 5-GHz band.

That could be appealing to some corporate sites, where 11b nets are already deployed, but which might want, or need, higher bandwidth. These sites would have the option of making use of 11g nets without having to incur the expected higher costs for the still-faster 11a LAN equipment.

Right now, corporate users are faced with the problem of having to use one card for one net, and a different card for another IEEE wireless LAN. That's because of the different frequencies and the different modulation schemes used for each one. If a corporation installs an 11b net today and then adds 11a access points for a streaming video application, 11b users would not be able to participate in the 11a net.

The Intersil proposal needs backing from 75% of voting IEEE task force members. If it gets that majority, the 11g task group will formally accept it, and then decide what changes or modifications to make to it. That final work could take up to 12 months. Otherwise, the task group will have to find other ways to smooth the migration from 11b nets today to faster nets in the future.

Intersil suggests taking part of the existing 11b standard, known as Complementary Code Key (CCK), and grafting it onto the modulation technique, called Orthogonal Frequency Division Multiplexing (OFDM), used by 11a. CCK would let the chipset handle 11b and, in future, 11g; OFDM would let the chipset also handle 11a nets.

By contrast, Texas Instruments proposed using an existing but optional part of 802.11, an encoding scheme called Packet Binary Convolutional Coding (PBCC), which is a technique that lets more data be packed into 2.4-GHz transmissions on an 11b net. TI's wireless business network unit, formerly Alantro Communications, already has 11b chips that include PBCC, which let those chips support maximum data rates of 22M bit/sec in the 2.4-GHz band.

Jim Zyren, director of enterprise and OEM products with Intersil's wireless division, says the proposal being voted on would simplify decisions for enterprise users, and give them a manageable migration path from 11M bit/sec nets today to faster nets in the future.

But nothing is simple in wireless LANs. William Carney, director of marketing for TI's wireless networking unit, says the vote may keep wireless LAN standards "in a very murky state" instead of clarifying them. "We're just going to see how things pan out," he says.

Although vendors and industry analysts report very strong 11b sales, they also say demand is only just starting, which means many corporate IT groups have yet to make a decision about wireless LAN investments at all.

In addition, prices continue to change rapidly in the wireless LAN market. Today's 11b equipment prices continue to fall. And LAN vendors say they expect 11a prices to be 25% to 50% higher than 11b prices, instead of 100% or more. If so, that will put starting prices for 11a interface cards at about $120, and about $1,000 to $1,200 instead of double those figures for access points. That's because better chip design has packed more components onto the chip, making 11a products simpler and less expensive to build.

If the price difference is not that great, will companies without wireless LANs today skip over 11b and go with the much higher data rates of 11a? Will they be willing to wait for the dual-band multipurpose 11g LAN products, which won't begin to appear until some time in 2002?

No one knows for sure, but wireless LAN users will certainly have some hard questions about the potential trade-offs of using dual-band radios compared with just changing over to high-rate 5-GHz technology.

"Most of these wireless nets are local, covering just one floor of a building," says Jay Gelman, software architect with Adrenaline Group, a Washington, D.C., consulting company that specializes in wireless deployments. "To make a change from 10M bit/sec to 100M bit/sec [wired] Ethernet, you have to change everything. But for a small wireless LAN, to actually change over from one set of equipment to another is not a big deal. You just pick a date and make the changes."

"If you have dual-band machines, it might make it easier [in some cases]," says Gelman's colleague Rob DiMarco, also a software architect. "But the question is, how expensive will these dual-band products be?"

In any case, both agree that most of their corporate clients are more concerned about wireless security than maximum data rates. "For the projects I've been involved in, bandwidth is not the overriding factor," DiMarco says.

Other observers think 802.11g may be irrelevant by the time products based on it finally appear, sometime in 2002. Atheros, a chip maker that just started shipping 5-GHz 11a chipsets to its LAN vendor customers, eventually supported the Intersil proposal during the May IEEE voting.

"By the time 11g products come out, so much 11a stuff will be [already] out there," predicts Mark Bercow, Atheros' vice president of marketing.

In addition, Bercow suggests companies may simply handle a mix of 11b and 11a nets in access points, rather than on clients. Several wireless LAN vendors plan to build access points that can take two interface cards: Corporate users can put a combination of 11a and 11b cards into each one to support users with different client cards.

Even if the September vote is a win for Intersil, corporate users eventually will cast their own, and more final vote . . . with dollars.

Contact Senior Editor John Cox

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