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A New Job for Wall Sockets: Networking


I have a problem at home. More and more networked entertainment products, such as the SONICblue Replay TV 4000 and the Hewlett-Packard de100c Digital Entertainment Center, need an Internet connection to download content and program guides. But I don't have a network connection in my home theater, if so grandiose a term can apply to a room barely big enough for a TV set, some audio and video gear, and a sofa.

Normally, I rely on Wi-Fi wireless Ethernet, but the entertainment gear isn't wireless-ready. And I didn't want to run Ethernet cable down a floor and across the length of the house. But a new technology called HomePlug power-line networking, which sends data down the electrical wiring of your house and turns any AC outlet into a network jack, turned out to be a simple solution to a vexing problem. And while I used it to extend an existing network, it will do just as well as the main way to link computers in a home.

I hooked up to my home's power lines with some HomePlug adapters from Linksys. They come in two varieties. One, called the PowerLine EtherFast 10/100 Bridge, is designed to connect to anything that has a standard Ethernet port, typically either a computer or a router or hub on an existing network. The second, the PowerLine USB Adapter, is designed for computers that lack built-in Ethernet ports, but is otherwise similar. Both are priced at a fairly stiff $150 apiece, but that price is likely to fall as production rises and additional producers enter the market. Linksys also plans to offer a $180 router that could directly link a cable or DSL modem to a power-line network. Currently, you need a router and a bridge to use power-line networking for a broadband connection.

Setup is simple for both adapters. You plug a computer directly into each HomePlug unit and set a password. Without this protection, there's a possibility that neighbors served by the same utility-company transformer could get into your network. Once all the HomePlug units have a common password, they can communicate through any power outlet in your house. I found that it worked seamlessly and speedy enough to get the full effect of a broadband connection. If only the adapters, which are big power bricks, nearly 7 inches long and 4 inches wide, looked good, too. Unfortunately, the circuitry required to separate the signal from the potentially lethal AC current makes these devices hard to miniaturize.

It's important, incidentally, to not plug the adapters into surge protectors, which can filter out the data signals. The effects range from seriously slowing down the data to stopping it altogether.

The idea of using power lines for networking has been around for a long time. After all, there are probably multiple outlets in every room in your house, and they are guaranteed to be linked through a common distribution system, or power bus. A technology called X-10 has been used for years for simple applications like remote control of lighting. But nasty technical problems, such as power spikes and sags or the electronic noise generated by electric motors, made power lines reliable only for very low data rates.

Last year a consortium called the HomePlug Powerline Alliance (www.homeplug.com) adopted a new industry standard based on technology from chip designer Intellon. The specification calls for speeds of up to 14 megabits per second over AC power lines running at 110 to 230 volts and at 50 or 60 Hertz. In other words, that's just about all of the residential wiring in the world. The products I tested were among the first based on the HomePlug standard.

The arrival of power-line networking brings a third practical networking choice into the home. The Home Phoneline Networking Alliance standard, which uses existing telephone wires, is relatively cheap, but it needs a phone jack for each computer, and these aren't available everywhere you have a power outlet. Wi-Fi wireless, which now costs less than $100 per computer, is the most flexible and is my first choice for most uses. But despite its drawbacks, HomePlug power-line networking now looks like it could be a worthy alternative, especially once the prices come down. By Stephen H. Wildstrom


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