Bright light: This experimental system can transfer data at one gigabit per second. An infrared laser (the black device on the right) is used to transmit the data.
Penn State University
Wireless optical networks could provide gigabit-per-second data transfer.
A wireless network that uses reflected infrared light instead of radio waves has transmitted data through the air at a speed of one gigabit per second--six to 14 times faster than the fastest Wi-Fi network. Such optical networks could provide faster, more secure communications and would be especially suitable for use in hospitals, aircraft, and factories, where radio-frequency transmission can interfere with navigation equipment, medical devices, or control systems. Another possible application is wireless networking for home theaters; a system that transmits data at 1.6 gigabits per second could broadcast two separate high-definition TV channels across a room, a capacity that exceeds the bandwidth of any existing radio system.
Penn State graduate student Jarir Fadlullah and Mohsen Kavehrad, professor of electrical engineering and director of the university's Center for Information and Communications Technology Research, built and tested the experimental system. Their setup sent data across a room by modulating a beam of infrared light that was focused on the ceiling and picking up the reflections using a specially modified photodetector. The pair says that their measurements show the system could support data rates "well beyond" the one gigabit per second they are currently claiming.
"This probably will be the next generation wireless communications technology," says Zhengyuan Daniel Xu, professor of electrical engineering at the University of California, Riverside. Xu is also the director of the UC-Light Center, a consortium of researchers working on wireless optical communications at different UC campuses. "Light will give you higher data rates than radio frequencies, and RF already has a very congested spectrum."
Optical wireless networks could also offer less interference and greater security than radio-frequency networks, Kavehrad says. While radio signals pass through walls and doors, light does not, making it easier to reuse frequencies and more difficult to intercept transmissions. He also notes that unlike radio frequencies, the spectral region for all light--infrared, visible, and ultraviolet--is unregulated worldwide. This could make it easier to commercialize optical wireless networks.
Researchers have studied indoor optical communications since the late 1970s, when engineers at IBM Zürich built the first working system. The technology languished because the Internet was still in its infancy, and there was no demand for wireless broadband systems--though interest has picked up in the past few years.
Kavehrad's demonstration is by far the highest speed that's been demonstrated for an indoor wireless optical network, says Valencia M. Joyner, assistant professor of electrical and computer engineering at Tufts University. She notes that the transmission distances that he and Fadlullah achieved, and their use of diffuse light rather than a point-to-point optical system, are especially important. "There are a lot challenges in demonstrating the high-speed capabilities of indoor optical signals," she says. "The fact that he was able to demonstrate a one-gigabit-per-second system with diffuse light is extremely significant. That drastically reduces the complexity of the transceiver system."
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I presented a similar idea at Caltech. Yes it is easy to go room to room or up and down the street. We demonstrated the drivers and receivers at Emerson Electric months later. No one was interested in economic exploitation. Good going Penn
Thanks to our CalTech colleague. One small correction, actually Penn State has been involved with this since before 1993. Please see the references below:
G. Yun, M. Kavehrad, “Spot Diffusing and Fly-Eye Receivers for Indoor Infrared Wireless Communications," Proceedings of IEEE Wireless Communications Conference, Vancouver, June 1992.
and also please see:
http://cictr.ee.psu.edu/research/wc/index.html
http://cictr.ee.psu.edu/CICTRnews/NEWS-IR/Nytimes.pdf
Thanks for your attention.
A similar setup was done by Psion and Acorn back in the 1990s here in the UK.
A classroom with lots of Psion 5 computers with their IR TX/RX devices pointing upwards to the ceiling where the network traffic is collected and passed to the teacher via a server.
I can't see this succeeding without a good implementation for room to room transmission. Certainly most office and home networks wouldn't be interested unless this limitation is overcome.
Actually, even without same speed/same technology room-to-room such a highspeed network would be worthwhile. A good many offices have rooms with hundreds of computers/printers, etc which could use such a network.
Even to set up a room with a few computers, without wiring, in just moments, as a super highspeed network would be a real advantage.
And the security....I want one!!
Even to set up a room with a few computers, without wiring, in just moments, as a super highspeed network would be a real advantage.
Don't those computers need power (wires) or is the power going to be transmitted wirelessly as well?
Ummm...batteries, as in laptop, netbook, iPad, Slate, etc etc ad nausium.
Consider powerline dead within the next few decades as resonant inductive coupling pushes forward. With wireless power transfer and the newest lithium air batteries there will be little need to run hard lines beyond a central grid.
As for optical data transfer, I seem to recall that Alexander Graham Bell developed his open air system over one hundred years ago, hmm. But, to answer the question of interroom transmission, it would not be that difficult to use a prism to split the signal and transmit to a low cost SOA in the wall that will rebroadcast in the adjoining rooms.
The article mentions the development of cheap white LEDs for home lighting. Perhaps the technology could be built into LED lighting systems, and the data could go through home electrical wiring. Could the signals be filtered such that they would not go out of the house, i.e., out to the general electrical infrastructure (for security)?
This is exactly the vision that the Penn State team (and others) are looking at: combining existing powerline data transmission technologies with general illumination LEDs to provide whole-home (or business) coverage. Obviously, there's a lot of engineering to be done to achieve this.
So far, I'm seeing one way communication here. from the optical source to the computer. But what about the other way around? A computer would have to have its own sending light and the optical source would have to have a reciever for the incoming light. Perhaps with many different device operating under this concept, they'd have to have their own assigned spectrum so there's no "stepping on" of another transmission.
This is a good point! We can suggest several alternatives. The simplest: use RF for uplink. Or as KeplersThirdLaw suggests: install a small photodiode with the light fixture on the ceiling and a small light source on the laptop, and connect them at a different wavelength. Thus, you have your perfect uplink with no interference to your downlink, and these uplink and downlink wavelengths would have to be standardized.
Powerline systems have failed to grain traction with consumers because they are expensive and don't work effectively. I have yet to find a Powerline system that will work even within the same room in my home. My home is less than 10 years old. 802.11g works flawlessly throughout my home.
I have had a powerline data link between two buildings working without a single failure for 3 years - that technology is not a bottleneck for this concept.
Powerline filtering is possible. Several companies produce powerline filters used in RF shielded enclosures. If you want high security, powerline filters should provide 100 dB insertion loss from 1 kHz to 10 GHz. Whether you want to spend the money to achieve this level of security is up to you.
As I recall, we already use IR for some in-house data transfer when we use a remote controller for the boob tube.
I really like the idea of IR for home or business use, since it's darn difficult to intercept that data.
Gary 7
On a first thought, it seemed that Infra-red light can be dangerous to health but after reading few articles on web, it appears that if used with slight causion, infra-red light has greater health advantages than risks.
I was just reading google's blog yesterday about an experimental fibre network which they plan to utilize in near future to provide 1 Gb/sec of trasnfer speeds.
So the future looks bright.
My friend, sunlight contains enormous amount of infra-red light. It is actually the reason for plants' growth! Therefore there is no harm and human beings have lived under that infra-red for ages.
I've seen similar technology before, except it was for beaming audio to individual with head phones on. Each set could have a different language. It worked pretty well unless you blocked the top of the box. The transmitters were in the ceiling of the rooms.
It seems that this could be important tech were security is needed, and you want to more closely control where the signal propagates to.
Brian
http://www.tooele-homes.com
Yes, light offers more security, control, and bandwidth too! IMAX has done something like what you say: using IR for audio transmission. 'Shadowing' or blocking of light occurs severely in line-of-sight links. In this case the light is diffused at the ceiling instead of having transmitters on the ceiling. Transmitters with larger field of views can also be mounted for better coverage at the expense of received power reduction. This is where multi-spot-diffusing and fly-eye receivers help. Useful reference: "Spot Diffusing and Fly-Eye Receivers for Indoor Infrared Wireless Communications" by G. Yun & M. Kavehrad published in Proceedings of IEEE Wireless Communications Conference, Vancouver, June 1992.
One thing about the security aspect. Yes, intercepting the signal would be more difficult than with wireless signals. Since it is diffuse lighting, you may get some transmission through windows or quite nicely through an open window. Don't forget about doors, even a closed door usually lets some light escape. Even in a sealed room, a well placed fiber optic cable in the ceiling would make for a pretty slick and nearly undetectable bug. If someone wants whatever is being transmitted badly enough they will find a way around the "security" of this method of transmission. That being said, unless you are working with some top secret data, this is would be quite useful for the consumer market where standard data encryption is acceptable for most users.
Manufacturing in the United States is in trouble. That's bad news not just for the country's economy but for the future of innovation.
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gubatron
5 Comments
Obstacles?
The first thing that comes to mind but I couldn't read any mention of it...
Will it work on another room? Say if this were to compete against WiFi (radio based), can you transfer data from your bedroom to another room separated by walls?, since it works on light it seems like it's not possible, or am I missing something?
Reply
Elroch
56 Comments
Re: Obstacles?
The simple answer is "no". But there are ways around it. A simple optical or infrared signal is stopped by any objects opaque in the relevant frequency, and walls are opaque in all the relevant frequencies. One can imagine various ways to build bridges between rooms, but these would obviously complicate installation greatly compared to an existing radio-based system.
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jmf414
5 Comments
Re: Obstacles?
Rooms are already connected with LV power lines, which earlier on have been demonstrated to have Gigabits per second data-transmission capacity. Electricity is ubiquitous, and Smart Grid/BPL will exploit that.
All the room lighting fixtures are connected to electricity for power supply, therefore room-to-room or floor-to-floor data transmission can be over existing LV power lines. The network infrastructure is already in place!
The interested reader is referred to "Triple Play using Power Lines and White Light Emitting Diodes for Home Networking" (http://cictr.ee.psu.edu/research/wc/index.html).
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