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DAZED AND CONFUSED

by Tom Cantrell

Start ý BalkLANization ý Pain in the Pan ý What's All the Buzz About? ý Rock Around the Clock ý Sources and PDF

BALKLANIZATION

Wireless Ethernet (aka, 802.11) is starting to take off. Already successful in the commercial world, it's now gotten to the point that Joe and Jane home users are starting to hop on board. With rising volume and falling prices, 802.11, despite it's commercial pedigree, is arguably a feasible alternative for embedded apps.

As usual, just about the time the waters start to clear it's time to stir them up again. That's no problem with 802.11, other than having to figure out which 802.11 you're talking about.

Anybody who's already running 802.11 has the "b" version (i.e., 802.11b). But, now there's an "a" version (802.11a) hitting the streets, with a "g" version not far behind. Check out the IEEE 802.11 home page, if you dare. There are a dozen or more task groups (if you're wondering about c, d, e, f, and so on) working on everything from security to quality of service (QoS) to worldwide harmonization. For now, it's enough just to focus on a, b, and g, which represent the main dilemma for designers and users of wireless gear (see Figure 1).

The controversy, as so often is the case, has its roots in the desire to increase network bandwidth beyond the 11 Mbps of the currently shipping 802.11b. The 802.11a alternative does just that, with a whopping 55 Mbps on tap. However, the extra speed rides on completely different waves in the 5-GHz band versus the 2.4 GHz used by 802.11b and a lot of other gadgets (cordless phones, BlueTooth, etc.). Thus, a and b are literally on a different wavelength, making them incompatible.

Enter 802.11g, which proposes to increase speed within the 2.4-GHz framework, thus maintaining compatibility with 802.11b, I think. You see, the 802.11g ratification was a bit of a tough go. Simply put, there was quite a knock-down, drag-out fight between TI and Intersil that threatened to ax the entire effort. Ostensibly centered around technical disagreements over modulation schemes and such, the battle wasn't so much about bits and bytes as back-room politics, bragging rights, and of course, bucks.

Eventually, what emerged as 802.11g appears to be a standard with enough options tacked on to placate all involved. There's enough wiggle room to make everyone happy, except users who face the daunting task of figuring out what it all means.

Consider the "declare victory" spin in the 802.11g press release from Intersil:

"Intersil will develop and market a new chip set that meets the proposed 802.11g standard by the second quarter of 2002. The new chip set will implement the proposal's mandatory CCK and OFDM modulation schemes, supporting data rates up to 54 Mbps. Intersil will not develop chip sets with the optional CCK-PBCC modulation. ýWe feel that the mandatory elements of the proposed standard meet all the needs of the market.'"

Meanwhile, TI countered with:

"Now that the technology behind 802.11g has been clarified, TI will be developing 802.11g-compliant devices by using elements of its existing 802.11b solution, as well as its 802.11a work in progress, for availability in mid-2002. Additionally, since TI's PBCC-22 is specified in the 802.11g draft, the company's existing devices, which already offer this higher rate feature, will be able to interoperate at 22Mbps with the company's 802.11g-compliant devices that will also offer PBCC-22. This ensures a high degree of forward-compatible interoperability at this higher data rate, while maintaining full 802.11b compliance. TI is currently shipping the ACX100 to customers offering 802.11b compatibility with 802.11g standards compliant 22Mbps extended data rates allowing them to quickly differentiate their products in a less confusing WLAN ecosystem."

Everyone clear on that? Don't you just love this business?

I personally have no idea what's going to work with what. At the least, it appears 802.11g gear based on Intersil chipsets won't exploit the 22-Mbps feature offered in TI's 802.11b chips. Users may well end up resorting to the good old Fry-and-try approach. Head over to Fry's Electronics (or your local version of the well-known Silicon Valley nerd supermarket), buy something, and give it a try. If it doesn't work, take it back and try something else.

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