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Weekly Column

Running Interference: There's a Big Threat to 802.11b Networking, Yet Nobody Seems to Care — Here's Why

Status: [CLOSED]
By Robert X. Cringely

There is a very good writer named Steve Stroh who specializes in wireless technology, and almost a year ago, he wrote an article that really disturbed me. You can get straight to his original article through one of the Links of the Week on this page, but for those who prefer the short version, Steve predicted the extinction of 802.11 WiFi wireless networking because of RF interference from a new kind of light bulb. This new lighting source uses RF energy to excite a gas that then glows brightly, which sounds a heck of a lot like a neon lamp, except this light, which comes from a company called Fusion Lighting, is supposed to be vastly more energy efficient than neon. This apparently catches us between a rock and a bright place: Do we want wireless LANs and satellite radio, or would we prefer to build fewer power plants and import less oil? Forgetting for a moment that this sounds like just the kind of story I might write, what's really interesting about it is that nobody but Steve Stroh and a couple satellite radio outfits seems to care. Then I figured it out.

Please read on.

I write this kind of story from time to time. A couple years ago, I reported that the FBI was going to be reading all the e-mail sent from public kiosks at this year's Winter Olympics. I thought I had a scoop. It sure felt like a scoop. People would be up in arms, I predicted, but hardly anyone responded. I was just too early. And following September 11th, most people were probably happy to know the FBI was on the job, however inefficiently. Maybe Steve was just a little too early with his story. After all, Fusion Lighting's products aren't even on the market yet. But you'd think the FCC at least would care. They worry that your PC will interfere with your TV and this Fusion Lighting thing, according to Steve, could wipe out WiFi coverage within a half mile radius of a SINGLE BULB. Replace all the street lights in a city and WiFi is dead.

But the FCC takes a benign view of interference in what is otherwise unlicensed spectrum. Anyone can play in the 2.4 GHz band, they say, as long as they play nice. And Fusion Lighting, for its part, claims to be playing nice, complying with every FCC requirement. I believe them.

This business of interference in unlicensed spectrum is going to be a bigger and bigger story over time. My friend Steve, who used to work for Cisco, tried to make a wireless link like mine to a building in downtown Santa Rosa. It didn't work, not because of any real technical difficulty, but because the WiFi spectrum downtown is dominated by a company called Broadlink. Steve could become a Broadlink customer, but he couldn't reliably smash through on his own over one of the three non-interfering 802.11b channels.

Yet Steve SHOULD have been able to get through, because Broadlink has to follow the same rules as the rest of us and not interfere. But the way the system actually works is that it is up to Steve to bring this to Broadlink's attention, demanding that they give him some space. And only if they don't can he begin the torturous process of getting the FCC to lean on Broadlink. In unlicensed bands like 2.4 GHz, the FCC just doesn't care all that much, so we are pretty much on our own. That's good, in that people like me can do 10 kilometer wireless links, and bad in that nice guys like Steve get stepped on.

In the case of Fusion Lighting, though, another principle is in effect. While Fusion's light bulbs may in fact cause interference for half a mile around (I don't know that they do, but it has been alleged), that interference doesn't affect ALL 802.11b traffic, just the fastest traffic. That's their loophole, and it's a good one.

WiFi supports two different spread spectrum technologies — Frequency Hopping and Direct Sequence. Frequency Hopping was Hedy Lamarr's original technique for jumping from frequency to frequency in a sequence known only to the transmitter and receiver, and thereby avoid eavesdropping by Nazi spies. Direct Sequence uses several frequencies at once, spreading the signal across the band. Both are secure, but only Direct Sequence can run at 11 megabits-per-second. Frequency Hopping is limited to two megabits-per-second in WiFi. But Frequency Hopping is also a bit more intelligent than Direct Sequence, and can adapt to interference by dropping from its hopping plan the frequencies where interference is worst. So while Fusion Lighting may well interfere with Direct Sequence networking for half a mile around, it probably won't interfere with Frequency Hopping networking, so there technically, is no violation of FCC regs.

What's funny about this, of course, is that almost nobody has their 11 megabit-per-second Direct Sequence WiFi network connected to the Internet at more than 11 megabits-per-second. MAYBE some businesses are connected at T-1 speeds, but most are DSL users, so the loss of performance from dropping to two megabits wouldn't even be noticed. In fact, it can be argued that Frequency Hopping makes so much more efficient use of the available spectrum that service might actually be better, not worse. Still, every user I know who sets up a wireless LAN chooses the 5.5 megabit or 11 megabit Direct Sequence settings, ignoring the 1 and 2 megabit Frequency Hopping options. Even my friend Steve, who should have known better, opted for the faster speed, which is probably why he got shut out by Broadlink.

So while there technically isn't a violation, you'd think the WiFi card and hub makers would be upset about this affecting sales. To the contrary, I think they secretly like it. You see networking technologies quickly become commoditized in today's market. When you can buy a 10/100 Ethernet adapter for $9.95, as I recently did, how much profit can the maker of the card be banking? Not much. That's why they like WiFi, because wireless hubs and adapters are earlier on the development curve and more expensive, which means more profitable. But if you've been pricing WiFi components, you'll notice they've dropped by half in the past year and will do the same and more in the next. They are being commoditized, and will eventually be designed directly into products or sold as $9.95 add-ons like Ethernet.

That's where 802.11a comes in. This follow-on to 802.11b not only runs at up to 54 megabits-per-second, it requires us to buy all new stuff. And 802.11a operates at 5.8 GHz, another unlicensed band that is completely free from light bulbs. THAT's why the WiFi manufacturers don't mind Fusion Lighting. By the time it is a factor — if ever — all Fusion Lighting will really do is get us all to move to 802.11a, making more money for the WiFi folks. They love it.

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