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BPL: The Better Broadband?
January 17, 2005

For 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.


Penn 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.


"Although 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.


Kavehrad 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 are unavailable."


Still, 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.


The 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.

Copyright 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.

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