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WiFi competitor uses visible light
Author: Gareth HalfacreePublished: 8th October 2008
The light-based wireless networking technology relies on 'smart LED' lighting being installed in a building.
According to Cellular News, a team at Boston University's College of Engineering is currently working on the ability to use LED lighting as a data communication channel, removing the need for a tethering wire while cleaning up the radio-frequency spectrum at the same time.
Professor Thomas Little paints a picture of a world where “your computer, iPhone, TV, radio and thermostat could all communicate with you when you walked in a room just by flipping the wall light switch and without the usual cluster of wires,” - so far, so WiFi. Where the project differs is in the use of visible light rather than radio waves: Little describes the system as “an LED-based communications network that also provides light - all over existing power lines with low power consumption, high reliability and no electromagnetic interference. Ultimately, the system is expected to be applicable from existing illumination devices, like swapping light bulbs for LEDs.”
While the project could feasibly work, there's a certain amount of assumption involved here: firstly, that we “switch from incandescent and compact florescent lighting to LEDs in the coming years” as a ubiquitous source of LED-based lighting is necessary for the system to work; secondly, that we're happy to have said LED lights turned on during the day.
While the speeds currently offered by the system – a projected 10Mb/s for the early generations – aren't anything to get excited about it's a system that certainly shows promise. Whether it would ever tempt anyone away from the now nearly ubiquitous radio-frequency based wireless networking technologies will remain to be seen – although the increased privacy available by simply drawing your curtains might have the paranoiacs enjoying wireless networking for the first time.
Would you be tempted by visible-light networking, or is it wireless networking already solved by current RF-based technologies? Share your thoughts over in the forums.
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Seriously, why do we pay these people? I want to get paid to come up with impractical solutions to problems that don't exist!
The problem with using visible (or even near-visible) light is that it's very easy to interfere with.
I can see what they're trying for with this one, but I'm a sceptic until further notice tbh. :p
At the very least, consider that such a system would depend on line of site. There would need to be a sensor oriented up or otherwise towards the light fixture transceiver. Unless you have uber-bright case lighting that is itself an immensely powerful light source, in proxiimity to or aimed at the sensor, everything should be fine.
Consider television remotes. These work via IR. Many lamps emit IR light as well. Does having a light on in a room prevent you from using an IR remote control with the television? Granted IR remote signals are modulated, but the TV sensor won't/shouldn't pick up non-modulated IR signals even of the same frequency.
Another thing is that LEDs typically emit at very specific wavelengths, and non-traditional colors emit at very specific color combinations. Maybe that "feature" can help in some way.
Ah, fair enough. I was asking out of curiosity, since I know jack about light and what has an effect on it.
That said, I did used to have my PC on my desk, back in the day when it was bright enough to blind the nearest person to it >.>
That is the most insane thing I have ever seen. Evesdropping on monitors?!
Time to make my monitor a tinfoil hat :D
TV remotes don't transfer masses of data though, they transmit a small amount of data loads and loads of times, and even then they can be a bit fussy.
As for specific wavelengths, yes, LED's emit a very small band of frequencies, but you will still get interference from other light sources, especially white lights.
Been there, it's called IRDA and used to be standard in mobile phones, laptops etc. ;-)
I can see so many draw-backs to this. And by the time we have LED lighting, if ever, there is no way that 10mb/s would even be remotely acceptable.
WiFi and other 2.4GHz signals (Bluetooth) also pass through your head...not to mention any RF technology that utilizes electromagnetic frequencies.
I would definitely advocate this new technology over the current RF standard. There are just one too many cancer patients out there who have faced the effects of constant electromagnetic interference. By using light waves as an alternative, this would not only reduce the effects of electromagnetic frequencies on the body, but it would also clear up the clutter of the current RF situation - all while providing better signal quality to current widespread RF technologies such as cell phones and short range wireless technologies.
I think you're a little confused about what "line of sight" means. Line of sight infers that there can be no scattering materials in the direct line from the transmitter to the receiver. As far as a 2.4GHz signal is concerned, there is NOTHING between the transmitter and the receiver because there's nothing in the way that's the correct size to scatter the signal, hence line of sight.
Longer wavelength signals can be bounced around obstacles (like long wavelength radio signals which can be bounced off the atmosphere and around the curvature of the Earth), hence they are not line of sight.
By your argument, visible light isn't line of sight either. Visible light propagates through a lot of material just to get to your eyes, the material just appears to be transparent.
Still, I just took a sheet of aluminum and placed it in the path between my router and client PC (in the next room) as close to the router as possible. After five minutes I disabled and reenabled to client's wireless card and waited some more. The signal quality was still excellent. Taking the masonry wall to be "transparent" there is now metal between the two wireless devices. I know you're not going to tell me that there is still "line of sight" communication between the two devices in this case.
Actually, I am. Now, if you had taken some aluminum mesh with holes spaced about 5cm apart and you would have been be able to completely block the signal.
Electromagnetic radiation doesn't care about what kind material is in front of it, it only cares about its geometry. If you have a material with the proper structure to scatter a signal, then you can block it or reflect/refract it sufficiently to make it appear like you're dissipated the signal completely, otherwise the signal will continue to travel in a straight line.
Here we go - back in 2004, a supermarket chain in the UK implemented a very similar system to control electronic shelf edge labels using a modulator in the starter for the florescent lights in the store... http://www.ilid.com.au/news/Retail%20Week%20UK%2022%20October%202004.pdf - the system is made by an australian company called ILID.
I would imagine that this new technology would be pretty much restricted to "broadcast" data - despite the pretty picture. Anyone remember "Internet over TV" - or even "Ceefax"?
Oh, and Goty... check your facts. I'm about 99% sure that a solid sheet of metal works just as well as a mesh - the trick with a Faraday cage is that you can use a mesh of the right size instead of a solid sheet. Have a look at the inside of your microwave if you don't believe me - the back and sides will be solid, and will block just as much of the radiation as the mesh on the door...
EM radiation *does* care what kind of material, it's blocked by anything that conducts and approximates an unbroken sheet... http://en.wikipedia.org/wiki/Electromagnetic_shielding
Having a physics degree does not make one immune to mistakes and naivety. For example, I needed to brush up on radio wave scattering and interactions to confirm that you were right in what you were saying.
Do you at least agree that an electric field cannot pass through a conductor?
Try to check your degree at the door to ensure that you don't treat anyone's opinion with undue bias.
If you'd like something better than my word, please reference "Introduction to Electrodynamics" by David J. Griffiths, specifically chapter 7. Also, you could google Ohm's Law, which is all I am referencing.
Now, to Ohm's Law. Sure, J = σE, and in the case where J is non-zero, there exists a non-zero E through a conductor. BUT we're talking about a metal sheet to which there is no emf applied. There is no emf and no otherwise induced currents, thus, the current density is 0. If J=0, E=0. So, in this case, the above statics principles apply, and you are wrong.
Take a radio - any radio, any frequency, and put it into a hollow metal cube. There will be zero transmission through that cube.
Let's talk about you metal cube example. How do you explain the fact that I can get a cell phone signal inside a corrugated aluminum building?