In the future, data may be transferred to laptops with the help of LEDs. Image: Fraunhofer HHI |
Regular
LEDs can be turned into optical WLAN with only a few additional
components thanks to visible light communication (in short, VLC). The
lights are then not just lighting up, they also transfer data. They send
films in HD quality to your iPhone or laptop, with no loss in quality,
quickly and safely.
Just
imagine the following scenario: four people are comfortably ensconced
in a room. Each one of them can watch a film from the Internet on his or
her laptop, in HD quality. This is made possible thanks to optical
WLAN. Light from the LEDs in the overhead lights serves as the transfer
medium.
For
a long time, this was just a vision for the future. However, since
scientists from the Fraunhofer Institute for Telecommunications,
Heinrich Hertz Institute HHI in Berlin, Germany, have developed a new
transfer technology for video data within the scope of the OMEGA project
of the EU, its implementation in real life is getting markedly closer.
At the end of May, the scientists were able to present the results of
the project in Rennes, France. They were able to transfer data at a rate
of 100 megabits per second (Mbit/s) without any losses, using LEDs in
the ceiling that light up more than ten square meters (90 square feet).
The receiver can be placed anywhere within this radius, which is
currently the maximum range.
“This
means that we transferred four videos in HD quality to four different
laptops at the same time,“ says Dr. Anagnostis Paraskevopoulos from the
HHI.
“The
fundamentals of visible light communication (VLC) were developed
together with the industry partners Siemens and France Telecom Orange
Labs,“ said the expert.
At
HHI, the team of project manager Klaus-Dieter Langer is now further
developing the new technology. For VLC the sources of light?in this
case, white-light LEDs?provide lighting for the room at the same time
they transfer information. With the aid of a special component, the
modulator, they turn the LEDs off and on in very rapid succession and
transfer the information as ones and zeros. The modulation of the light
is imperceptible to the human eye. A simple photo diode on the laptop
acts as a receiver.
“The
diode catches the light, electronics decode the information and
translate it into electrical impulses, meaning the language of the
computer,“ says Langer.
One
advantage is that it takes only a few components to prepare the LEDs so
that they function as transfer media. One disadvantage is that as soon
as something gets between the light and the photo diode (for example,
when someone holds his hand over the diode) the transfer is impaired.
Laptops, Palm devices or mobile telephones are all potential end
devices.
The
scientists emphasize that VLC is not intended to replace regular WLAN,
PowerLAN or UMTS. It is best suited as an additional option for data
transfer where radio transmission networks are not desired or not
possible?without needing new cables or equipment in the house.
Combinations are also possible, such as optical WLAN in one direction
and PowerLAN for the return channel. Films can be transferred to the PC
like this and also played there, or they can be sent on to another
computer.
The
new transmission technology is suitable for hospitals, for example,
because radio transmissions are not allowed there. Despite this fact,
high data rates must be transmitted without losses and unzipped,
according to the experts. If part of the communication occurs via the
light in the surgical room, this would make it possible to control
wireless surgical robots or transmit x-ray images. In airplanes, each
passenger could view his own entertainment program on a display, saving
aircraft manufacturers miles of cables. Another possible venue for the
application of this technology are production facilities, where radio
transmissions very often interfere with the processes.
Currently the scientists are developing their systems toward higher bit rates.
“Using
red-blue-green-white light LEDs, we were able to transmit 800 Mbit/s in
the lab,“ said Klaus-Dieter Langer. “That is a world record for the VLC
method.“
The
HHI scientists will showcase how videos are transmitted by light in
Hall 11.1, Booth 8 at the International Telecommunications Fair IFA
(Internationale Funkausstellung IFA) in Berlin from September 2-7, 2011.
