19 January 2005

Power lines could blow away DSL, cable

Overhead electric power lines have the potential to provide bit rates that far exceed DSL or cable over similar spans.

"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 two or three megabits per second," said Mohsen Kavehrad, Penn State University's W.L. Weiss professor of electrical engineering and director of the Center for Information and Communications Technology Research.

"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," Kavehrad said. "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."

"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," Kavehrad said.

Kavehrad said 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.

"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," he said.

"In service, performance will depend on how close the power company chooses to place the repeaters."

Kavehrad said they will solve the engineering issues to make BPL a technical alternative to DSL and cable. The question on whether it will be an economical alternative remains, since there are interference issues they need to overcome.

For related information, go to www.isa.org/networks.