Wi-Fi alternative2006-01-12 00:06:27
engineers have shown that a white-LED system for lighting and high
data-rate indoor wireless communications, coupled with broadband
over either medium- or low-voltage power line grids (BPL), can offer
transmission capacities that exceed DSL or cable and are more secure
Colored LEDs or light emitting diodes are currently
found in the numbers on digital clocks, remote controls, traffic
lights and other applications. Recently, white LEDs have emerged in
the market and the tiny white lights are being considered as
replacements for incandescent and fluorescent bulbs.
Some researchers predict that by
2012, tiny white LEDs will deliver light brighter than a 60
watt-bulb yet draw only as much current as provided by four D-size
batteries. A Japanese team recently suggested using white LEDs not
only for lighting but also as light sources for wireless in-house
Now, Dr. Mohsen Kavehrad,
the W. L. Weiss professor of electrical engineering and director of
the Center for Information and
Communications Technology Research, and his team have shown
that, in the system they designed, coupling white LEDs to BPL can
deliver secure, wireless bit rates of a gigabit per second, a rate
only exceeded by fiber.
Kavehrad will detail the Penn State
system and its performance in simulation in a paper, "Hybrid MV-LV
Power Lines and White Light Emitting Diodes for Triple-Play
Broadband Access Communications," at the IEEE Consumer
Communications and Networking Conference in Las Vegas, Nev.,
Tuesday, Jan. 10. His co-author is Pouyan Amirshahi, a doctoral
candidate in electrical engineering.
In the Penn State
system, white LEDs are positioned so that the room is lit as
uniformly as possible. Since the LEDs are plugged into the room's
electrical system, broadband data, voice or video delivered via the
power lines can piggyback on the light that fills the room to reach
any wireless receiving devices present.
Since light does not
penetrate walls, as do the microwaves used in RF, the white LED
system is more secure. In addition, there are no known health
hazards associated with exposure to LED light.
notes, "Optical path differences can cause signal distortion in
high-speed data transmission. This distortion is highly dependent on
the room's dimensions and system configuration. However, if a system
is designed appropriately, this distortion can be minimized. For
example, in our proposed system, at worst, distortion limits the
data rate to one gigabit."
Although white LEDs are not yet
commercially available for this type of application, Kavehrad is
confident that they will be. He says, "White LEDs are not there yet
but by 2010, they will be available and economical. Their low-energy
consumption will make them especially attractive. In the future,
when you turn on the lights for indoor low-cost lighting, you could
receive broadband via the same white light LED. "
The study was supported
through Penn State's Center for Information and Communications
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