Print 100 comment(s) - last by William Gaatje.. on Oct 16 at 11:43 AM

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. 

Comments     Threshold

This article is over a month old, voting and posting comments is disabled

RE: Another problem
By William Gaatjes on 10/7/2008 5:04:55 PM , Rating: 2
And indeed the current through the led is important. The best led powersupplies are current regulating and not voltage regulating. The voltage over the led is fairly constant.

RE: Another problem
By mindless1 on 10/9/2008 12:56:03 AM , Rating: 2
Any LED power supply has to be current limiting or it's defective. You could hand-match one constant voltage PSU to one hand-picked LED with a tested voltage:current ratio but this could never be a cost effective manufacturing strategy.

There would necessarily have to be processing of what the data rate vs frequency result was in total light output so the voltage increased as the frequency changed to transmit data. It is attainable, no question about that, but the issue is doing this cost effectively in *every* light module installed when the present disincentive in deploying LED lighting is already the (for most uses) excessive cost per lighting module.

Actually, the voltage over the LED will not be constant within the idea of data TX/RX, it is necessarily going to rise and drop below an emitter threshold at the frequency needed to achieve the desired data rate, at a minimum the voltage will cross a forward voltage/die threshold in the KHz range and probably higher considering their claims of data throughtput rate.

RE: Another problem
By William Gaatjes on 10/10/2008 5:36:56 AM , Rating: 2
Led's are current driven devices. To get the best results you need a current controlled power supply. This means that the voltage varies when the load (the led) varies because of temperature fluctuations. Good old Ohm's law U = I * R.
No handpicking there, just a good led regulator ic.

The led's will be just switched on and off at a high rate afcourse.
With the dataspeeds mentioned in the article i would say it would be megahertz. We have optocouplers that can switch that fast. But i think the switching frequencies of the led's will be much lower and multiple leds with their own part of the spectrum are used to obtain a parallel nature of sending data.

When there is no data to be send , the led's emit there colour at a controlled current set point.

RE: Another problem
By mindless1 on 10/12/2008 2:05:09 AM , Rating: 2
Actually no, the voltage doesn't vary it is current controlled and the heatsink is a constant so the temp should not vary significantly. You could make it more elaborate in an outdoor installation, in some cases that might be reasonable but for practial economical design choices, it won't happen.

They will vary voltage to some extent, to achieve a median brightness value during data TX/RX, to achieve roughly the same average current. That much will be necessary as consumers won't want lights that aren't at constant intensity. The practical applications will depend on budgetizing the design, people won't pay a lot for built in optical networking in every light fixture when a wifi router can be had for $10 total that covers several rooms, and the client adapters equally inexpensive.

RE: Another problem
By William Gaatjes on 10/12/2008 7:51:53 AM , Rating: 2
Please do some reading up on the specification of diode and Light Emitting Diodes. Also, please look at Ohm's Law.

RE: Another problem
By mindless1 on 10/15/2008 4:55:10 AM , Rating: 2
Diodes are not a resistive load, Ohm's law is not applicable. Please do some reading on diodes.

RE: Another problem
By William Gaatjes on 10/16/2008 11:22:38 AM , Rating: 2
Diodes are not resistors, i know they are non linear components. It is for the sake of simplicity i used Ohm's law for example. I don't have to read, i know the characteristics from diodes from memory. I see it simple, to make a led that has a spectrum similair to a ordinary bulb or what is even better day light, You can pick and bin all you like but a led lamp build from multiple led's is easy to calibrate for the desired color temperature. Because of the way led's produce light.

RE: Another problem
By William Gaatjes on 10/12/2008 10:48:59 AM , Rating: 2
There is something called thermal resistance. The junction temperature of these led's are much higher then the temperature of the heatsink. For a common example, CPU heatsinks do not reflect the actual temperature of the hotspots present in the cpu die.

And when the material get's hotter, more current starts to flow. That's why led's are current driven devices. And the more power you draw, the more serious it get's.

RE: Another problem
By mindless1 on 10/15/2008 4:56:02 AM , Rating: 2
I never claimed otherwise, but it is not linear and your basic statement of it has no direct bearing on the conversation.

RE: Another problem
By William Gaatjes on 10/16/2008 11:43:05 AM , Rating: 2
Actually no, the voltage doesn't vary it is current controlled and the heatsink is a constant so the temp should not vary significantly. You could make it more elaborate in an outdoor installation, in some cases that might be reasonable but for practial economical design choices, it won't happen.

Read your own post please as the quoted section comes from your post.

Please read up on current sources.

Also when looking at the I/U graph of a standard diode, You wil notice that for small forward voltage changes large current changes happen.

"Well, we didn't have anyone in line that got shot waiting for our system." -- Nintendo of America Vice President Perrin Kaplan

Copyright 2016 DailyTech LLC. - RSS Feed | Advertise | About Us | Ethics | FAQ | Terms, Conditions & Privacy Information | Kristopher Kubicki