Making 802.11 Standards Work Together

By Carmen Nobel  |  Posted 2001-07-23 Print this article Print

Interoperability difficulties are keeping wireless deployments on hold

WLANs may have been around for several years, but that alone wont entice Tom Miller.

"We have elected to wait until 2002 before taking any plunge into wireless LANs," said Miller, senior director of corporate IS at Affymetrix Inc., in Santa Clara, Calif., and an eWeek Corporate Partner. "This hesitancy has been due to evolving standards, the mix of vendors in the market, security and anticipated price reductions as volume increases."

Considering the alphabet soup that the technology has become, IT managers like Miller can hardly be blamed for their confusion—and hesitancy. Indeed, the Institute of Electrical and Electronics Engineers standards body governing WLAN technology has subgroups that have subgroups. To date, the results of their work are the 802.11 standard. And then, of course, theres 802.11a, b, e, f, g, h and i.

Of these, only products based on 802.11b, also known as WiFi, are available. Running in the 2.4GHz band, they boast speeds of 11M bps. Products based on 802.11a, which runs up to 54M bps, are due from companies such as Atheros Communications Inc. by the end of the year. But 802.11a products run in the 5GHz band, rather than the 2.4GHz band, and are therefore not compatible with 802.11b products.

Enter 802.11g, which aims to offer data rates as high as those of 802.11a, but with 802.11bs 2.4GHz range.

"[802.11g]s whole thing is that the preamble in the packets is something that 11b can understand," said Jim Lansford, chair of the IEEE coexistence study group, which deals with interference issues among the 802.11 standards. "All the stuff thats being deployed right now is based on 802.11b," so backward compatibility could be important.

But the adoption of 802.11g has been slow going because of a fight between industry giants Texas Instruments Inc. and Intersil Inc., each of which is pushing different techniques of transmitting data. Most companies on the committee tend to favor Intersils solution, but after a weeklong IEEE meeting earlier this month that was supposed to settle the matter, the 802.11g issue remains unsettled.

"Basically, they spent a week discussing Roberts Rules of Order," said Mark Bercow, vice president of business development at Atheros, in Sunnyvale, Calif.

802.11g, then, is stalled at least until September, which is when the next IEEE meeting takes place. 802.11a has a more definite product road map, but some IT managers wonder whether they should forgo 802.11a and wait for 802.11g.

"This is a real can of worms, and theres a lot of money involved," said Lansford, who is also vice president of business development at Mobilian Corp., in Hillsboro, Ore., which builds radios that enable competing wireless technologies to run in close proximity. "Theres a school of thought that says [802.11g] stalls [802.11a]."

In the meantime, there are more lettered subgroups dealing with problems inherent in existing WLANs. 802.11i, for example, is working on plugging security holes in the 802.11 standard, although "the reality is that anyone who was planning to have their whole security system based in the encryption features of 802.11 was looking for trouble," Lansford said.

Its unclear when the 802.11i group will propose a solution to the main committee. The 802.11e group, meanwhile, is working on quality-of-service issues in the media access control layer of the 802.11 protocol, which will ensure that streaming video and audio will work well over WLANs. 802.11e is in the beginning of the approval process.

And if there werent enough letters in the mix, the Federal Communications Commission must ultimately assure that all devices running in the 2.4GHz and 5GHz bands will play fair with one another. The 2.4GHz band is infamous for housing both the Bluetooth standard and 802.11b, which can interfere with each other. The 5GHz band has its own issues because it houses 802.11a and several mobile satellite services.

"Many of these devices use spread spectrum, which tends to be relatively immune to interference, but as you might expect, if you pack enough things close enough together, theres always the possibility of interference," said a senior official at the FCC, who asked to remain anonymous. "Earlier this year, we started a ruling looking at additional things we can do to allow products to share spectrum with reduced chance of interference."

Chief among these, he said, is a technique called adaptive hopping, which could let Bluetooth and other frequency-hopping technologies seek out empty portions of a band rather than blindly hopping all over it. Currently, adaptive hopping is against the rules, but the FCC is looking into changing those rules. Again, though, with myriad wireless companies and the government involved, its a slow process.

Customers said its hard to know what to think because so many iterations of the 802.11 standard are not on the market yet. "Right now, we are doing what we call a proof of concept with 802.11b," said Erich Berman, a technical consultant for the IS department at Northwestern Mutual, in Milwaukee. "Since [802.11b] is a fully supportable standard, were going with it for the time being. ... [The others] are of interest to us, and Ill follow them closely. [But] we need to stick to standards that are fully fleshed out in the industry."


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