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An artistic rendering of the new light-driven wireless network in action.  (Source: Boston University)
Could the networks of the future run on light

Solid-state lighting is one of the hottest topics in the tech industry, and with good reason.  The Department of Energy is sponsoring a $20M USD "L Prize" for advances in LED lighting, a type of light which uses solid-state components (diodes).  The research is a big deal as lighting currently consumes 22 percent of the electricity in the U.S.  If the DOE accomplishes its goals of reducing lighting energy use by 50 percent, it would save billions of dollars and reduce environmental impact.

New research from Boston University's College of Engineering, funded by a National Science Foundation grant, indicates that LEDs may be not only the integral lighting component of the future, but may also form the backbone of future wireless networks.

BU Engineering Professor Thomas Little describes the new research, stating, "Imagine if 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.  This could be done with 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."

The primary goal of the research is to develop LEDs that do exactly that -- transmit information wirelessly via controlled blinking. 

Little continues, "This is a unique opportunity to create a transcendent technology that not only enables energy efficient lighting, but also creates the next generation of secure wireless communications.  As we switch from incandescent and compact florescent lighting to LEDs in the coming years, we can simultaneously build a faster and more secure communications infrastructure at a modest cost along with new and unexpected applications."

Professor Little and his colleagues imagine LED lighting in the room being hooked up to computer circuitry, which uses existing lighting to implement a wireless network which provides data to computers, personal digital assistants, television and radio reception, telephone connections and thermostat temperature control.  Prototypes of the new network design, according to Professor Little, should start at around 1 to 10 Mbps.  Better yet, bandwidth would be greater than in existing radio frequency (RF)-driven networks.

In the new network, each LED light bulb would act as an access point.  Another perk of the new design is beefed up security.  Unlike RF networks, the new signal would not pass through walls or other opaque objects.  This would help prevent snooping and connection theft.  The new system would also use much less power than RF, as solid state lighting is energetically cheaper to the strong radio signals needed for wireless internet. 

The flickering which drove the network would be performed so fast the human eye could not see it.  The network would ideally be able to operate outdoors as well as indoors.  The first test deployment may be outdoors, with a likely candidate being car interiors.  Professor Little continues, "This technology has many implications for automobile safety.  Brake lights already use LEDs, so it's not a stretch to outfit an automobile with a sensor that detects the brake lights of the car in front of it and either alerts an inattentive driver or actively slows the car."

While the technology seems very promising, one quandary is how to make the communication bidirectional.  Professor Little and his team have not elaborate on this tricky point yet in the initial press.  In order to send data requests, you would need a means of receiving light from devices such as cell phones or laptops, however, you ideally would want to avoid having to have a bright blinking transmitter on your device walls covered in sensors. 

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RE: Another problem
By Solandri on 10/7/2008 4:54:56 PM , Rating: 3
That's not as big a problem as most people think. Light bounces off walls and other stuff. Your TV remote uses an IR LED. Try pointing it at the wall behind you instead of at the TV. Usually it'll still work.

LOS is more important for radio applications, where you're dealing with noise and greater signal degradation. Due to radio's longer wavelength, it passes through many objects we consider solid. Light OTOH bounces off most of these (except transparent stuff). So there's less noise and signal degradation in the visible light spectrum.

RE: Another problem
By MrTeal on 10/7/2008 10:31:03 PM , Rating: 3
Honestly, I think you have it backwards. LOS is much less important in long wavelength communications, because it passes through materials better and suffers much less atmospheric extinction. The higher the frequency, the more important line of site becomes. Reflections are generally not a good thing; they might help in some trivial applications like a TV remote, but in any higher bandwidth applications, things like multipath can cause huge issues.

RE: Another problem
By BWAnaheim on 10/8/2008 9:22:04 AM , Rating: 2
Good response. Not only would reflections cause multi-path problems from your light/network source to your networked device, but if you notice the picture, the room has a line of desks. Now, the reflections off objects on your desk will cause interference to the networked device for the person at the next desk. Light scatters when it hits objects through which it cannot pass, which is why a single light source can illuminate more than one point. This scattering effect will cause an increased noise floor in a room with multiple users, to the detriment of throughput.

As for the flicker effect, not only do televisions flicker, but so do fluorescent bulbs. While this flicker is noticeable on bulbs with old ballasts or ballasts that are going bad, high frequency fluorescent ballasts like those used in CFL are noticeable under normal operating conditions. I imagine that these new devices will flicker at about 20 MHz to achieve the throughput speeds quoted, so this flicker should be invisible to the human eye. As I was writing this response, though, I recalled that interference patterns between multiple light/network sources may become visible if the differences in flicker rates are within the range of the human eye and the difference in light intensity in those interference zones is also detectable by the human eye. Think of this as the fluorescent light effect on a CRT television or monitor.

If the office has only one light source or a few light sources, these problems could possibly be alleviated, but then people will have problems receiving the light on their networked devices-- their eyes. I think that this solution is an interesting study, but the practical application is going to see some major implementation issues in my opinion.

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