Back in the Stone Age of home networking, anyone who wanted to play on a computer not hooked directly into an Internet connection had to snake phone lines or Ethernet wires across floors and up staircases.
People talked about a promising idea: using the electrical wiring already in the house to move data from room to room. One early application, the X10 system for controlling lights and appliances, didn't always work well. The technology was certainly not ready to be used to bring Web pages to computers anywhere in the house.
Along came the wireless network. For $50, you could get the Internet sprayed across the house and never be tethered by a cord to the wall. It was slow in those early days, notoriously unreliable, and open to interception if you couldn't bother with setting up the encryption codes.
But it caught on. According to estimates made by Parks Associates, a market research firm based in Dallas, about 12.5 million homes now have wireless networks; another 10 million homes, mostly newer ones, have Ethernet or coaxial cables in the walls.
Cheap and ubiquitous is a hard combination to beat. But wireless networks did not end the quest to put data through electrical wires.
Technology companies continued to work on the idea. Some tried using phone circuits. A version for power lines called HomePlug came out in 2002, and while it hardly affected sales of wireless network equipment, it sold enough that major companies like Intel, Cisco, Sony, Sharp and Comcast created the HomePlug Alliance to push for next-generation products, with the first to come out later this year.
"I don't think anyone had expected the technology to progress," said Andy Melder, senior vice president for sales, marketing and business development at the Intellon Corporation, a maker of chips for home networking devices that use power lines.
Some companies are not waiting. Panasonic, Netgear and Marantz are already offering products that will move data through home electrical lines faster than routers using the current Wi-Fi standard for wireless networking, 802.11g.
Panasonic started selling its HD-PLC Ethernet adapters for power lines last month. A $200 starter kit provides two units, each about the size of two sticks of butter.
One adapter is attached to a router with a short Ethernet cable and plugged into a nearby wall outlet. The second device is plugged into an outlet elsewhere in the house. When a computer is linked to it with an Ethernet cable, data is transmitted through the home's electrical wiring at speeds of up to 190 megabits a second. Up to seven devices can run on the network.
Netgear, a leading maker of wireless networking gear, will be selling a similar system next month for about $300. (Every additional module costs about $150.) It moves data at a slightly faster rate.
Marantz says its ZR6001SP receiver will send music to special speakers in another room over power lines. The system, which includes both devices, will sell for about $1,300. Additional speaker units cost about $300. The music listener controls the receiver and the CD players or iPods connected to it from a control pad on the speakers.
"We were getting many requests from installers, like how do I get multiroom audio if I can't run wires," said Kevin Zarow, vice president for marketing and product development. The Marantz device also solves the problem of running speaker wires across a room.
At first blush, these products may seem to be nonstarters. After all, who would want to pay two or three times the price of a wireless network?
The answer lies in the simplicity.
Robert Stephens, founder and "chief inspector" of the Geek Squad installation and troubleshooting division at Best Buy, said installing wireless networks was the leading reason for house calls. "It's why most people need us," he said, noting that the complexity of installing a wireless network is evident from the fact that return rates on wireless networking devices drop to nearly zero when his installers do the work.
The Panasonic network over power lines, on the other hand, was up and running in less than five minutes. Encryption was automatically enabled, and there was no need to configure anything. It worked well even in a house with 90-year-old cloth-wrapped tube-and-knob wiring where the lights sometimes flicker. And though Panasonic warns that operating a power drill or a vacuum cleaner on the same outlet may cause an interruption of Internet service, running both while using the HD-PLC on the old wiring did not pose a problem.
The makers of all three products said that people who cannot get whole-house coverage with a wireless system or those plagued by dead zones might find it appealing.
But the real selling point for the technology is that it can transmit high-definition video without pixelating or skipping. It can claim that advantage over wireless networks — at least for now — because it has a higher data transmission rate.
"Three years ago, the majority of devices connected to a home network were home computers," said Mike Timar, national marketing manager for Panasonic's communications and home office electronics division. "But today there are MP3 players, game consoles and high-definition TV."
Wireless routers using the 802.11g standard move data at 54 megabits a second. That's fine for Web pages, but too constrained to move a high-definition video image, which needs about 85 megabits of capacity. The Panasonic and Netgear products have more than enough room to handle that, as will the HomePlug devices coming out later this year.
The next-generation wireless routers, using the 802.11n standard, will also transmit about 200 megabits a second, but a network may initially cost $150 to $250, erasing the cost advantage that wireless now holds.
Pitching the device to the next generation of TV watchers with high-definition televisions and DVD players also pulls in the market for game console users who might want to run multiplayer games from multiple rooms. It also neatly sidesteps the argument that wireless is more convenient.
"If you are watching TV, you don't care about mobility," said Kartik Gada, Netgear's networking product line manager.
There is a hitch, however. The three companies' products are not compatible with one another. Nor are they compatible with the products adhering to the standards set in August by the HomePlug Alliance.
Netgear and Panasonic jumped the gun on the standard out of frustration with what they said was the slow pace of the alliance. (Marantz is using a system called DAvED, which stands for digital audio via electrical distribution.)
"Not going with a standard-based approach is problematic," said Mr. Melder of Intellon, who is also a spokesman for the HomePlug Alliance. "It tends to freeze the consumer."
Panasonic executives said the company's breaking of the ranks would not necessarily create compatibility problems in the long run. They said a second standards group, the Consumer Electronics Powerline Communication Alliance, is working to ensure that all the networking devices for power lines could coexist and communicate.
There is something that all the makers of such gear, including Netgear and Cisco's Linksys unit, can agree on. People will probably end up having both wireless and wired connections in their homes.
Within about 18 months, cable companies may start offering set-top boxes with networking abilities over power lines. Computer makers, as well as television and DVD makers, will do the same. At that point, all a consumer will have to do is stick the power plug into the wall and the data will come racing down the wires with the electricity.
后记:上学那会儿,我偶然在一个网站上看到一则新闻,介绍一种利用普通电线传输Internet数据的技术原理,并且当时技术上还有很多难题,好像只是停留在理论上,实现则显得遥遥无期,我当时觉得很新鲜,但因为没有具体应用,就掠过了.没想到现如今这种技术居然可以挑战现行的无线技术市场地位,让我有些吃惊.原来这种技术相比传统无线技术,在视频媒体的传输上还遥遥领先,因为现行无线技术的传输速度一般为54M/s.而下一代无线标准802.11n上市之后,在其价格的据高不下,也将是这种"无线"技术迅速占领市场的先机,且看它如何运筹.
一些有用的链接,可以帮助你了解更多这种技术的信息:
[1] The Consumer Electronics Powerline Communication Alliance
[2] HomePlug Powerline Alliance
[3] NetGear: Wired and Wireless Networking Solutions for the Home, Business, and SOHO Networks.
[4] Panasonic's communications and home office electronics division
[5] Marantz: Home Theater by Marantz
[6] Intellon Corporation:电力线通信的世界领导，为家庭网络、网络娱乐、电力宽带接入和商业 应用提供HomePlug(R) 适应和其他电力线整合.
[7] PLC-J
[8] 北京意科
[9] The Universal Powerline Association: UPA - Home