Optical wireless and broadband over power lines: High
speed, secure Wi-Fi alternativeJanuary 12,
2006
Penn
State 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 than
RF.
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 communications.
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.
Kavehrad 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. ”
Penn State
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