POSTSCRIPT / December 18, 2011 / Sunday


Philippine STAR Columnist

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Wi-Fi to Li-Fi: Send data via light bulbs!

SHIFT TO LEDs: Why are some of your friends replacing their incandescent light bulbs with LEDs (light emitting diodes) and switching from LCD to LED television sets? Possibly, they want to cut their electricity bill for lighting by almost half.

The LED lamps sold in the malls cost three to six more, but are super economical in the long run. Being more energy efficient, they give greater illumination for the same wattage as your old bulbs (you can light your room with just three 3-watt ceiling LEDs) and last longer (50,000 hours).

This basic household use of LEDs is just one of many applications existing and in the offing.

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HASS ON SHIFT: An exciting use of LEDs in the future is the transmission of wireless data via light bulbs. Rather than rehashing an article on the subject and risk distorting it, we pass it on to you straight from The Huffington Post, slightly compressed.

University of Edinburgh’s pioneering Harald Haas discusses in HuffPost alternative uses of LED light bulbs, presaging a shift from Wi-Fi to Li-Fi (Light Fidelity):

“When we use smartphones or tablet PCs to surf the internet, check emails, share pictures, engage in social networking, or store information in a cloud, we use wireless communications technology.

“Traditionally, all the information we move around with these devices is transmitted using radio frequency spectrum. The more data we generate, the more radio frequency spectrum we need. It is forecast that by the year 2015, we will transmit six exabytes — six billion, billion bytes — every month through wireless networks. This is a ten-fold increase on the amount of data we send now.

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“TO MEET this increased demand, we need either 10 times more radio frequency spectrum for commercial wireless networks, or we have to make the existing radio frequency spectrum 10 times more efficient.

“The first is impossible — most of the available radio frequency spectrum is already used. The second option is difficult to achieve, as existing wireless technology is very sophisticated, and it has been shown that further improvements are often offset by unmanageable complexity.

“Therefore, we are heading to a saturation point in terms of how efficiently we can use the radio frequency spectrum. The only way out of this is to find new ways to transmit data wirelessly.

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“FORTUNATELY, the electromagnetic spectrum not only incorporates the radio frequency spectrum, but also includes the visible light spectrum, the best known transmitter of which is the sun.

“In the past we used incandescent light bulbs in our homes and offices. This technology is more than 100-years-old and, as such, is hugely inefficient. In the past decade, there have been massive developments in the use of light emitting diodes (LEDs). Since LEDs are far more energy efficient than incandescent bulbs, they are at the heart of the latest generation of lights.

“Research by my team at the University of Edinburgh has shown that, if all the world’s incandescent light bulbs were replaced by LED, the energy saved would be equivalent to that produced by more than 100 nuclear power stations.

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“HOWEVER, this is not the only advantage of LEDs. These lights are semiconductor devices similar to transistors, which are commonly found in devices such as TVs, laptops or smartphones. Like transistors, LEDs can be switched on and off very quickly.

“We have harnessed this feature to develop novel techniques that enable ordinary LED light bulbs to wirelessly transmit data at speeds many times faster than Wi-Fi routers. We have named the new technology Li-Fi (light fidelity) which we now commercialize via the university spin-out company VLC Ltd.

“In our lab, under ambient light conditions, we are able to achieve data speeds of 130 megabits per second. If all light bulbs were able to do this, it would create a simple, energy-efficient solution to the lack of available radio frequency spectrum for future wireless broadband communication.

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“THE NEW Li-Fi technology utilizes existing infrastructures and as a result the installation costs are minimal, let alone the reduced cost of the technology as it does not require an antenna.

“On top of this, there are other advantages to this technology. Light does not penetrate walls, and so internet signals cannot be intercepted outside the room in which they are transmitted, which enhances security.

“Light also travels through water, and so short-range underwater communication is possible. For instance, divers could share pictures, or remotely operated vehicles could exchange information.

“Light is inherently safe and can be used in places where radio frequency communication is often deemed problematic, such as in aircraft cabins or hospitals. So visible light communication not only has the potential to solve the problem of lack of spectrum space, but can also enable novel applications.

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SALLY’S DAY: “In the not-too-distant future, the life of an average person (we’ll call her Sally) could look like this:

“When Sally switches on the light in the morning, she gets the latest news flashed on her smartphone. From the breakfast table she sends a few emails through the table light.

“As Sally drives to work, a cat darts crosses the street and she has to brake hard. Her LED backlights tell the car behind to slow down even before the driver has a chance to brake — an accident is avoided.

“Sally stops at a red light using LEDs. While showing red, the traffic light sends a signal to switch off the engine in Sally’s car, reducing CO2 emissions. The traffic light communicates with the car’s navigator, helping Sally avoid a traffic jam ahead.

“In the office, Sally’s fast internet access is provided through the LED ceiling lights. She has internet access in all meeting rooms, but no one outside can intercept the signals.”

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(First published in the Philippine STAR of December 18, 2011)

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