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Beaming data could be networking's saviour
Researchers have seen the light, and it
could be your network of choice sooner than you think, writes David
Gallagher.
Researchers of infra-red networking would like to bounce data
off your nose. Or your desk. Or the coffee machine.
Their goal is to use beams
of infra-red light, reflecting from all surfaces in a room, to create
high-speed information networks. While local networks using radio waves, such
as Apple's AirPort system, have been getting the attention, scientists
working on infra-red say that in the long run, light might be a better and
faster alternative.
"Radio cannot
compete with this performance," said Mohsen Kavehrad, a professor of
electrical engineering at Pennsylvania State University.
Kavehrad and a
colleague, Svetla Jivkova, have been researching a system that sends
pencil-thin infra-red beams bouncing around a room, connecting computers to
one another and to a central transmitter and receiver that is wired to a
larger network. The researchers said the technology could transmit two gigabits
a second, or about a thousand times as much data as a cable modem, with few
transmission errors.
Anyone who has used a
remote control to change the channel has seen infra-red in action. The
technology is also used in laptop computers and Palm-type devices for
wireless communication over short distances. But these links work best when
the transmitter is pointed at the receiver, something that would not be
practical when linking an entire office or offering network access in a
public place like an airport or a restaurant.
One way around the
problem is to bounce wide infra-red beams off the ceiling, scattering the
reflections around the room. This allows receivers to be pointed in any
direction. While some networking products already use this approach, Kavehrad
said the scattered beams created something similar to an echo, causing data
loss and limiting the network's speed.
The researchers think
they have solved the echo problem by using a holographic filter to produce
thin beams that create a large grid as they reflect around the room. The
university is seeking a patent on the technology.
"It's a really cheap
and easy way of producing these multiple beams," he said. "Having
the pencil beams allows you to send the signals very fast, and not relying on
just one of them allows you to move around, and you can do this whole thing
at low power levels."
Researchers at the
University of Kassel and at the University of Siegen, both in Germany, have
approached the problem differently, focusing on improving the receiver's
ability to separate signals from echoes and interference. The researchers say
the resulting network would be fast enough to allow everyone in a meeting to
receive and transmit video streams on their laptops simultaneously for
videoconferencing.
Providing enough
bandwidth for activities like videoconferencing is one area where infra-red
has an advantage: the radio spectrum is tightly regulated so only certain
frequencies can be used for data transmission. Manufacturers can push into
higher frequencies in search of free space but at the same time the
components need to become more expensive.
Infra-red has no such
problems because its frequencies, which are just below visible light on the
electromagnetic spectrum, are unregulated. And because infra-red
transmissions do not penetrate walls, there is no chance of interference or
overlap in neighbouring rooms. That also can be a security advantage:
radio-frequency networks open the possibility of eavesdropping, perhaps by
someone sitting in the parking lot with a laptop and an antenna.
But infra-red's
inability to pass through walls and other objects may also be its downfall.
The technology requires at least one receiver and transmitter in each room to
be connected to a wired network. This makes it an unlikely choice for, say,
someone wanting to stay online wirelessly while moving a laptop among
different rooms. And forget about going online from the backyard via
infra-red - the beams need surfaces, particularly ceilings, to bounce from.
One thing that might
boost infra-red would be research demonstrating that the radio energy used in
mobile phones and other devices is actually hazardous to human health.
At the low level of
energy needed for networking, researchers say, infra-red beams cannot hurt
the eyes or anything else.
Kavehrad said that he
was concerned about the long-term effects of bathing people in radio waves
and that infra-red light offered a safer alternative.
"We've lived under
God-given sunlight for zillions of years," he said.
The New York Times
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