Penn State engineers have developed a new model for
high-speed broadband transmissions over U.S. overhead electric
power lines and estimate that, at full data rate handling
capacity, the lines can provide bit rates that far exceed DSL
or cable over similar spans. Dr. Mohsen Kavehrad, the W. L.
Weiss professor of electrical engineering and director of the
Center for Information and Communications Technology Research,
led the investigation. He says, "Although broadband power line
(BPL) service trials are now underway on a limited basis in
some locations in the U.S., these trials run at DSL-
comparable rates of 2 or 3 megabits per second.
"We’ve
run a computer simulation with our new power line model and
found that, under ideal conditions, the maximum achievable bit
rate was close to a gigabit per second per kilometer on an
overhead medium voltage unshielded U.S. electric power line
that has been properly conditioned through impedance matching.
The gigabit can be shared by a half dozen homes in a
neighborhood to provide rates in the hundreds of megabits per
second range, much higher than DSL and even cable."
Kavehrad adds, "If you condition those power lines
properly, they’re an omni-present national treasure waiting to
be tapped for broadband Internet service delivery, especially
in rural areas where cable or DSL are unavailable."
The researchers say they are the first to evaluate
data rate handling capacity for overhead medium voltage
unshielded U. S. electric power lines and will outline their
findings at the IEEE Consumer Communications & Networking
Conference in Las Vegas, Nev., Jan. 5. Their paper is titled,
"Transmission Channel Model and Capacity of Overhead
Multi-conductor Medium-Voltage Power-lines for Broadband
Communications." The authors are Pouyan Amirshahi, a doctoral
candidate in electrical engineering, and Kavehrad.
In
their paper, the authors note that the junctions and branches
in the U.S. overhead electrical grid cause broadband signals
to reflect and produce multipath-like effects on these lines.
This causes degradation in power-line broadband transmission
performance and decreases transmission capacity.
Kavehrad explains, "The signal can bounce back and
forth in the lines if there is no proper impedance matching.
The bouncing takes energy away from the signal and the loss is
reflected in the ultimate capacity. "In service, performance
will depend on how close the power company chooses to place
the repeaters," he adds.
The researchers are
continuing their studies. Kavehrad predicts that the
engineering issues to make BPL a technical alternative to DSL
and cable will be solved. Whether it will be an economical
alternative remains to be seen since there are interference
issues that have to be overcome.
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