BPL: The Better Broadband?
January 17, 2005
several years, power companies and their supporters have promoted
broadband over power line (BPL) as a viable alternative to DSL and
cable Internet access technologies. But new research indicates that BPL
may not only be another broadband choice, it may be a better choice.
State University engineers have developed a new computer model for
measuring high-speed broadband transmissions over U.S. overhead
electric power lines. They estimate that, at full data rate handling
capacity, BPL lines can provide bit rates that far exceed DSL or cable
over similar spans.
broadband power line 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," observes Mohsen Kavehrad, the Penn
State professor of electrical engineering who led the investigation.
"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," he says. "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," says Kavehrad, who is also director of Penn State's Center for
Information and Communications Technology Research.
views power lines as a ready-made, super high-speed Internet access
infrastructure. "If you condition those power lines properly, they're
an omnipresent national treasure waiting to be tapped for broadband
Internet service delivery, especially in rural areas where cable or DSL
BPL must overcome several technical hurdles before it can become a
mainstream Internet access technology. Kavehrad notes, for example,
that junctions and branches in the U.S. overhead electrical grid cause
broadband signals to reflect, producing multipath-like effects on power
lines. This effect causes degradation in power-line broadband
transmission performance and decreases transmission capacity. "The
signal can bounce back and forth in the lines if there is no proper
impedance matching," Kavehrad explains. "The bouncing takes energy away
from the signal and the loss is reflected in the ultimate capacity." In
service, performance will depend on how closely the power company
chooses to place its repeaters, says Kavehrad.
Penn State researchers are continuing their studies, and Kavehrad
predicts that BPL's engineering challenges will eventually be solved.
But whether BPL will ever become an economical alternative to cable or
DSL remains to be seen, since there are still political issues that
have to be resolved. Over the past few years, BPL has encountered
fierce resistance from some radio spectrum users, particularly amateur
radio operators, who claim that spurious signals radiated by the
technology interferes with their operations.
© 2004 PricewaterhouseCoopers. PricewaterhouseCoopers refers to the
network of member firms of PricewaterhouseCoopers International
Limited, each of which is a separate and independent legal entity. All
rights reserved. The preceding article was written by John Edwards, a
freelance technology writer based in Gilbert, Arizona. He can be
reached by phone at +1-480-854-0011.