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Plug in, Turn on, Surf Away

September 2001
By Henry S. Kenyon

Applications link devices via power lines.

Internet access may soon be as close as the nearest electrical outlet. New power-line networking technology allows voice, data and video signals to travel through standard electrical lines, turning building or campus electrical grids into ready-made communications pathways. Connected by devices similar to modems that are plugged into wall sockets, computers and smart appliances can be linked together or to existing fiber optic lines without extensive installation costs.

The ability to connect information devices through electrical lines has existed for a number of years, but technical difficulties limited the technology to industrial applications such as linking machinery on factory floors and in nautical and mass transit systems. Recent breakthroughs in signal processing technology have created the potential for homeowners and small businesses to install local area networks without fiber optic lines. Power-line technology also offers a potential last-mile connectivity solution for older facilities.

Although power-line networking technology has operated successfully in industrial and commercial niches since the early 1990s, it is the allure of a larger home market that is driving the industry, explains Seth Libby, an analyst with the Yankee Group, a Boston-based industry analysis firm. Initial development in the late 1990s indicated that the technology was on the verge of a major market breakthrough, but Libby notes that unrealistically high expectations about the technology’s promise affected the industry’s image after researchers encountered technical difficulties. The power-line industry has since regrouped.

Several industry alliances have been created to generate standards, provide expertise and raise awareness. Among the largest is the HomePlug Powerline Alliance, which comprises 90 companies backed by major electronics firms. HomePlug released its first standard specification for high-speed home-power-line networking in June. The specification provides a guide for alliance members to develop interoperable products that will allow home computers, peripheral devices and smart appliances to connect through home power outlets.

Prior to the release, HomePlug conducted extensive trials in 500 homes and 10,000 wiring paths in the United States and Canada. According to the alliance, the tests determined that the specification met regulatory, interoperability, performance, noninterference, reliability, scalability, diagnostic and maintenance requirements. The standards help the industry by providing an incentive for investors to furnish the money to refine the products, Libby explains.

According to Michael Propp, president and chief executive officer of Adaptive Networks Incorporated, his company was among the first in the industry to market the technology. The Newton, Massachusetts-based firm manufactures microprocessor chips for power-line devices, circuit cards and modems—self-contained units that can serve as a node in a power-line network. He notes that Adaptive’s equipment connects the cash registers in many U.S. department stores. The firm’s technology also is used to network the display signs on commuter and subway trains in Montreal, Mexico City, Paris and Hong Kong. Other applications include meter-reading devices, controllers for refrigeration units and voice communications in mines.

Adaptive’s chips provide signal processing and error correction functions. Each chip consists of a physical layer and a media access central (MAC) sublayer. The physical layer controls how a signal is placed on the line, how it is received and synchronized, and what error correction is performed. The MAC layer allows networked devices to send data packets to each other in an orderly manner by managing this communication, Propp explains.

Power-line communications devices use electrical wires and cables as a medium. They do not require any power to actually flow through the wires. Propp notes that data transmissions travel at much higher frequencies than the 50 to 60 hertz generated by alternating current. However, one of the problems the technology faces is noise and signal attenuation generated by the different devices plugged into a network. Attenuation causes interference, blocking broadcasts at certain frequencies in an unpredictable fashion. This phenomenon can vary at different locations and times on a length of electrical line, he says.

To avoid noise and attenuation difficulties, Adaptive’s power-line microprocessors conduct signal processing operations and synchronize data transmissions. Data packets are detected at the beginning of a transmission, and the message is equalized across the network as each receiver corrects the distortion produced by the power-line environment, Propp says.

Current home networking devices have projected speeds ranging from 2 to 10 megabits per second. HomePlug’s new standard covers devices with speeds up to 14 megabits per second. A 10 megabits per second threshold is compatible with Ethernet devices, but tests determined that average performance will be lower. Trials conducted by the alliance found that more than 80 percent of test homes saw average throughput speeds of 5 megabits per second. Propp believes that the technology is capable of considerable speed increases, perhaps with throughput rates as high as 40 to 50 megabits per second in certain applications. However, he cautions against hype because it undermined earlier efforts by the industry. There is a considerable difference between marketing claims and an application’s actual delivered data payload, he says.

However, the technology does have potential as a last-mile solution, Libby explains. “It’s an alternative to the local telephone company’s copper loops, the cable companies coaxial cable, and in some cases, an alternative to fixed wireless solutions.” After initial expectations fell short, many firms worked on refining their devices. Several firms currently are testing home networking systems that will begin reaching the marketplace in the fall.

Mark Isaacson, chief executive officer of Ambient Corporation, Brookline, Massachusetts, explains that last-mile connectivity issues are very important for home and small business users. He believes that home networking is “a bridge to nowhere” without Internet connectivity. Power-line devices allow a wide array of devices to be networked: cable top boxes, home gateways, radio frequency, wireless and Ethernet. “There are a variety of ways to do it. But how do you connect the customer, keep broadband speeds and improve service? This is where the thrust of the business is, and that’s why I think access is starting to get so much attention,” he says.

While government, military and major commercial institutions could benefit from power-line networking, Isaacson admits that they are secondary markets compared to homes and small businesses. But despite this emphasis, firms like Ambient also will network office buildings and other facilities, he says.

Older buildings and historical sites hold a major potential market for power-line networking because the technology represents perhaps the only way some structures can be economically rewired, Isaacson says. He notes that even if fiber optic lines were built to the curb of every household, it would cost between $20,000 and $200,000 to rewire an average American home, depending on the location. Laying fiber optic line also can be very expensive, with average per-mile costs ranging from $300,000 to $700,000. Once the line is laid, last-mile issues still persist. “The problem with laying fiber is that you’re still dealing with regular wiring, twisted pair, copper, analog—whatever it is within the existing building. There is no other medium that offers the ability to use existing infrastructure comprehensively the way power line does,” he says.

Ambient is developing a power-line networking system that will work on both low- and medium-voltage power grids. Isaacson claims that his company’s technology has been tested on energized and de-energized lines in neighborhoods. “We are building a system that integrates the functionality of an entire system, both low and medium voltage. The difference is that low voltage would most likely run on a distribution transformer system that has somewhere between hundreds to many hundreds of homes on it,” he explains.

Low- and medium-voltage systems will create two sets of services. The first is the home consumer and small business market that is the industry’s current focus. Applications include Internet access, telephony, streaming video, and pay-per-view movies. Additional services may include alarm monitoring, controlling home power demand and intelligent appliance management.

Utility companies form the second major market. Not only can a number of telecommunications services be provided through power lines, but also utilities can use power-line networking technology to make their services more efficient through applications such as peak shaving—limiting power consumption during high demand periods, load management and intelligent demand-side management. Other potential services could include niche products to aid distributed generation, real-time pricing, remote generation of power services, substation-to-substation telecommunications and metering.

Isaacson believes that power-line networking technology will help utility companies become more efficient and provide both top and bottom line revenue enhancement. He notes that if a major regional utility such as Continental Edison were to experience a systemwide failure lasting for more than 90 minutes, it would stand to lose up to a year of profits. This damage also extends to all of the regional businesses relying on the power and their losses. “If we can help cure 10 percent of that, we’ll have done a tremendous service to the country and to businesses,” he says.

Yet despite recent advances, power-line networks still face some technical hurdles. They can be indirectly affected by external events such as power fluctuations. However, because the technology uses the system’s wires and cables to transmit signals, connectivity can be maintained even if there is no power on the lines. Propp notes that while power fluctuations may cause some devices to malfunction or generate additional noise, they are not a threat to network viability.

Propp observes that a final barrier is translating these technologies into functional devices. “Part of that hurdle is simply getting stuff out there that really works adequately for mainstream uses. The second is translating that effort into commercial and industrial applications at higher speeds, and that’s not trivial,” he says.

Another potential difficulty is the direction networking in general is taking, Propp says. Consumer networking technologies are moving toward a multimedia approach, providing audio, video, intercom and video security capabilities. He explains that all of these applications require broadcast and multicast capabilities because they function by sending out information to many different nodes from one transmitter. These systems also require what Propp calls “quality of service” capabilities that create multiple data streams with their own different transmission requirements functioning simultaneously on the same line. He notes that video and audio need different requirements than data streams because while packets can tolerate delays, the minute gaps are noticeable with music and video.

However, developments in the past year have put power-line technologies on the brink of wide market release, Isaacson says. By 2002, he expects the technology to create substantial commercial opportunities. As opposed to hype, this new market will have solid technical and financial foundations. “Real customers with real economics and real business built around it,” he says.

Additional information on power-line networking is available on the World Wide Web at http://www.homeplug.org, http:// www.ambientcorp.com, and http://www.adaptivenetworks.com.