Internet over your power line?

By Dave Wallace - 110 Portside Lane

Imagine someday plugging your PC into a wall receptacle and being connected high-speed to the Internet. No phone line, no cable, no wireless and no satellite. Simply by plugging into an AC receptacle you connect to the Internet from any room in the house.

It's called BPL or Broadband over Power Line and it's a new technology used to deliver high-speed Internet access via existing electrical wiring. It benefits power companies as well but does have some downsides. We'll talk about them but first let's mention a BPL system currently operating in Cincinnati (google Cincinnati BPL) that now has about 8,000 customers.

Cinergy (now Duke Energy) is the local power company serving Cincinnati. They contracted Current Communications to provide Internet high-speed service over their power lines. Internet data begins on a fiber optic cable run from the power company's network hub out to each neighborhood they wish to serve. It is there that the fiber optic cable connects into the company's 7,500-volt transmission line that feeds step-down transformers in the area. The radio frequency of the Internet data is in the 1-30 MHz spectrum as it becomes superimposed on the 7,500-volt line. Since there's no way for low-power data signals to pass through step-down transformers a coupler provides a path around the transformer to allow it to transit from the 7,500 volt line down to the 240-volt line into homes without degradation. The technology used within each home's AC wiring is called HomePlug networking, which is an existing technology used to provide networks within a home.

So here we have another way to connect customers to the Internet. In the beginning, we could only get Internet into homes over plain old telephone service (POTS) and then came Digital Subscriber Line (DSL) that beefed up POTS to handle faster digital data instead of analog. Then the TV cable folks learned how to add Internet at higher speeds to their cable and finally radio access via satellite or wireless ground stations appeared. Power line access is thus a new way to reach the Internet and one that may grow rapidly but everything is not as rosy as BPL advocates would like you to believe. There could be trouble ahead.

Power lines are designed to carry electrical power at a frequency of 60 Hz. The problem with BPL is that it uses radio frequencies in the 1-30 MHz spectrum whereas the attenuation characteristics of power lines make them suitable for only about 20 kHz, and perhaps up to 350 kHz at a stretch. Note kilohertz, not megahertz. So this means you're not going to get too far putting a 1-30 MHz signal on a 7,500 volt power line because the higher the frequency the higher the attenuation. Increasing the radio signal makes matters worse by radiating interference to other FCC radio services. Some detractors believe radio interference will be the death knell to BPL service.

One might think that BPL is not new because power companies have been transmitting radio signals over their lines for years to control equipment. But they only transmit data around 100 - 180 kHz for low speed commands like "turn a relay on or off." Although power lines act like antennas, low frequency power signals are not known to cause interference problems like BPL may cause.

How fast can Internet data be transmitted over BPL? All sorts of numbers are tossed around and with so many tests going on and results not being made known it's hard to tell. In the Cincinnati system they claim to be offering download speeds at 512 Kbps to 3 Mbps, which is comparative to DSL and broadband cable. But other stories abound. Like aluminum house wiring can slow your speed to 2 Mbs and if a repeater is needed on the pole outside your house it could limit the bandwidth to 2.5 Mbs and if used at your circuit breaker box you could be down to 1.0 Mbs. Some customers may not find BPL as rosy as advertised. But the same thing happens with DSL and broadband cable so what else is new? Time will tell. The jury may still be out on BPL Internet service.