Engineers have been experimenting with using power lines for communications since the 1950s. But broadband over power lines, or what the Europeans prefer to call power line communications, has long been one of those just-around-the-corner technologies that holds a great deal of promise in principle but has never quite taken off.
Still, having witnessed earlier boom-and-bust cycles and continued lobbying by ham radio operators to have the plug pulled on the whole idea, makers of equipment that turns electrical outlets into Internet data ports believe that power line communications is now poised to mount a serious challenge to digital subscriber line, or DSL, and cable Internet services.
Why? Enabling technologies on both the transmission and consumer ends have made the service easier to deliver at an attractive price. The technology will have what is essentially a monopoly in most rural areas and many other places that DSL and cable Internet services do not reach. And consumers naturally would like to have broadband connections that give them more options for where they work or play. "There is definitely interest in the ability to plug your notebook into an electrical socket anywhere in your home or while traveling," says Michael Koch, vice president of strategy and regulation at Power Plus Communications AG, a division of the German electric utility MVV Energie AG in Mannheim [see photo, ].
With DSL or a cable modem, depending on where your lines or jacks happen to be, sending e-mail wirelessly from the back porch on a sunny day may be nothing more than a daydream. Even with a Wi-Fi base station in place, running the IEEE 802.11 standard, some spots in the house are bound to get better reception than others. But if your utility company has installed power line communications equipment on the poles in your neighborhood, you have a lot more flexibility: attach a Wi-Fi port--say, Apple Computer's new AirPort Express--to a power line modem, and you can plug the wireless data port in anywhere there's an outlet.
With such possibilities in mind, a number of U.S. utilities announced trials of new power line communications services this year. Electric power companies such as Cinergy, Consolidated Edison, and Progress Energy have reported encouraging results, with thousands of households from California to Ohio signing on. A demonstration house set up by Current Technologies LLC near its headquarters in Potomac, Md., has attracted wide interest from utilities, investors, and the press.
The second wind in power line communications is largely attributable to the advances made by engineers at Intellon Corp., a small, fabless designer of advanced ICs based in Ocala, Fla. The main problem was noise. Power lines are a rough-and-tumble environment for data compared with coaxial cable and twisted-pair copper lines. They are subject to unpredictable sources of interference, such as the motors of appliances like vacuum cleaners and sewing machines.
Intellon largely solved the noise problems, and thus the reliability problems, of power line networking while making it cheaper to implement, more secure, and easier to use. So potent was the buzz about the company's groundbreaking INT5130 chip set--the first to offer a minimum throughput speed of 10 megabits per second (with the promise of scalability to even higher speeds), digital encryption, and compatibility with other home networking technologies--that leading home and business networking companies Netgear, Linksys, and SMC Networks all announced products based on Intellon technology to meet standards set by an industrial alliance called HomePlug.
(HomePlug originally was formed to standardize data networking over electrical wiring inside the premises but has since expanded its scope to include power line communications.)
Intellon's chip sets combine orthogonal frequency division modulation, dozens of carrier channels, and automatic channel switching. This design ensures that data packets using power lines as an on-ramp to the information highway can switch lanes when they encounter problems, such as varying impedances, narrowband interference, and impulse noise, that are inherent to that medium. The result: data suffers less loss.
Other important advances came from technology providers like Current Technologies and Andover, Mass.-based Amperion Inc. Current Technologies makes a device that serves as a direct link between an overhead medium-voltage line and the 220-volt line running to a house, so data packets can avoid the transformers that step down the voltage and would destroy the data [see photo, ]. Amperion's Falcon 1000 repeater/extractor, when installed on medium-voltage transmission lines, limits attenuation by catching the data packets, repackaging them, and sending them out again. It can also route packets to low-voltage lines.
Optimism about the technology comes just as the United States and the European Union have declared that universal access to broadband Internet service is a high priority. Earlier this year, the European Commission launched an initiative aimed at driving standardization of power line communications (PLC). Called the Open PLC European Research Alliance (OPERA), it is set with funding of ¤20 million in its first two-year phase. "The goal is to standardize this technology in much the same way Europe collaborated to establish [a single] cellular phone standard," says Power Plus's Koch, who is also a member of OPERA's steering committee.
More than 35 European energy companies, telecommunications equipment manufacturers, consultancies, and universities have so far agreed to participate in OPERA--a boon to the European utilities that stuck with power line communications and already are offering limited commercial Internet service. These include Electricite de France SA, Endesa SA in Spain, MVV Energie AG in Germany, and the Scottish and Southern Energy Group in Scotland.
It's a big change from the 1990s, when news of power line communications was much more about failure than success. Nor.Web, a partnership between the Canadian communications gear maker Nortel Networks Corp. and United Utilities Electricity PLC, in Manchester, England, succumbed to technical problems that integrated circuits available at the time could not overcome. Nortel, seeing little chance of recouping the millions of dollars needed to develop reliable products and market the service, concluded that the technology would remain a niche product at best.
One of the bigger problems, now apparently solved, was noise. But another, almost as serious, was an uncertain regulatory environment. The German electronics giant Siemens AG, in Munich, had once hoped to be at the forefront of the technology but dropped its plans in 2001, citing regulatory delays and a lack of European standards. Several German utilities, notably E.ON Net GmbH and RWE AG, also pulled the plug on their power line communications services.
Regulatory issues are far from fully resolved, even now. The main issue keeping officials up at night is signal interference. U.S. ham radio operators have complained about the effect of power line transmissions on their communications signals, while some regulators have voiced concerns over privacy following reported cases of eavesdropping.
In Germany, "we have had acute cases of radio interference being reported--in the range of 30 to 40 decibels," said Thilo Kootz, an engineer with the German ham radio club DARC e.V. in Baunatal. "And consider this: the European Commission, which has helped fund the development of the shortwave Digital Radio Mondiale [DRM] technology, now seems willing to destroy this new FM-quality system with its support of power line communications."
To convey high-speed Internet into homes and businesses, power line communications providers must transmit their data in the form of radio signals. These signals typically have a frequency between 2 and 80 MHz, meaning they occupy the same frequency range used by hams, CB radio users, and aircraft operators. Ideally, the signals would remain confined to power lines, but because these wires are not shielded in the way coaxial cable is, they often behave like long antennas.
When this happens, "there is noise over an area of several blocks from the power line, to the point that that's the most dominant thing you hear in a radio receiver," says Paul Rinaldo, chief technical officer of the American Radio Relay League (ARRL), a national organization representing ham radio operators. "When there's significant data transfer, you might not be able to hear anything for several seconds."
In fact, the ARRL, based in Newington, Conn., says its field tests have shown serious distortion of amateur radio signals when a ham antenna is located within 30 meters of an overhead power line containing a single broadband communications device. The ARRL has also expressed concern that using power lines for high-speed data transmission would limit the ability of ham operators to engage in emergency communications, which it says are crucial for homeland security.
Amperion is currently testing ways to notch out ham frequencies to ensure that its products do not run afoul of the stringent interference rules of the U.S. Federal Communications Commission (FCC). But amateurs report that the company's efforts have met with mixed success. "We've seen some cases where it's helpful and others where interference persists," Rinaldo says.
A few years ago, the European Commission asked experts to come up with a solution. "After two years, the differences were such that the group couldn't come to an agreement," said Holger Hirsch, a researcher at the University of Duisburg-Essen, in Duisburg, Germany, who is an expert on radiological phenomena such as electromagnetic fields and conducted emissions that are caused by power line networking gear.
FCC Chairman Michael K. Powell has said that power line technology can help "expand the availability and affordability of broadband." The commission is proposing new measures that will limit on-air noise as much as possible.
The rules would include a requirement that power line communications services reduce power levels and exclude problematic frequencies if complaints are raised, and one demanding that providers have the capability to deactivate power line communications devices in case of serious noise.
Through it all, Rinaldo remains optimistic that hams, the broadband over power line providers, and the FCC will eventually come to a workable compromise. "We've been through problems before with television interference and things like that, and ultimately, they do get managed," he says.
--Willie D. Jones
With reporting by Elizabeth Svoboda and John Blau