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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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