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Using LED Ceiling Lights For Digital Communication
PatPending writes "A Minnesota start-up company, LVX, is developing products under several patents and about a dozen pending applications, e.g., 'Building illumination apparatus with integrated communications, security and energy management,' that put clusters of LEDs in a standard-sized ceiling light fixture. The LEDs are in optical communication with special modems attached to office computers. The first generation of the LVX system will transmit data at speeds of about three megabits per second, roughly as fast as a residential DSL line. LVX Chief Executive Officer John Pederson said a second-generation system that will roll out in about a year will permit speeds on par with commercial Wi-Fi networks. It will also permit lights that can be programmed to change intensity and color. Pederson said the next generation of the system should get even more efficient as fixtures become 'smart' so the lights would dim when bright sunlight is coming through a window or when a conference room or hallway is empty. Hurdles: speed and installation costs. No word on the reliability and security of this system."
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What one fool can do, another can. (Ancient Simian Proverb)
Kohls has had technology like this in their stores for a little while now. They use the lights to update little LED price tags throughout the store. I think Fujitsu makes the tech, though I could be wrong. Anyone wanna help me out on this?
IRDA doesn't flicker in the visible spectrum, and thus fails to cause hilarious non-fatal seizures in coworkers, which, I'm assuming, is the whole point of this new technology.
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
They're also working on a getting a patent for a new modem where you just set the phone headset right on the modem, by sticking both round parts in little earmuff thingies. Apparently it's only good for a couple hundred bits per second now, but they claim the next version will reach speeds in excess of 1000 bits per second. No word on whether it will work with cell phones.
The first generation of the LVX system will transmit data at speeds of about three megabits per second, roughly as fast as a residential DSL line.
Is that physical layer rate? If so, what's the rate after protocol overhead?
Let's assume that is the physical layer rate. Which would make it three and a half times slower than 802.11b, and 18 times slower than 802.11g, which is virtually everywhere. And, drumroll please, at least one hundred times slower than 802.11n, which is 300-600Mbit/sec (physical layer speed.)
Please help metamoderate.
With enough power, you could certainly saturate whatever receiver tech they are using(presumably some sort of reasonably high speed photosensitive semiconductor, TFA isn't clear on what kind); but in the visible spectrum that sort of thing would be pretty noticeable. If they are actually just including some IR LEDs in their lamp array(which isn't entirely unlikely, "white" LEDs, since they are phosphor-coated blues or UVs, actually have lousy switching speeds because the phosphor keeps glowing momentarily after the diode is turned off. Though they could, I suppose, be using RGB arrays, which would have full switching speed...) "flood" interference would be less obvious; but still pretty unsubtle.
Because of little things like "eye safety" and "that guy in the truck with the generator and 5kw of stage lighting is pretty obvious at 300 meters" the classic "directional antenna and illegal power levels" that works so well on Wi-Fi probably won't work on this thing. On the other hand, TFA makes the company sound like they decided to go it alone, develop all their own patented tech and protocols and stuff. If the history of RF is anything to go on(Why hello WEP and the assorted nameless 900mhz and 2.4ghz cordless phone systems, we were just talking about you...) people who do that tend to make protocol and/or cryptographic mistakes. Assuming this stuff ever gets out of complete obscurity, I assume that snarky grey-hats will be flooding the system with garbage frames at defcon and you'll be able to buy little LED flashlights from ebay that exploit buffer overflows and execute arbitrary code on the microcontrollers in the ceiling fixtures...