New network technologies vie to carry video

As devices that record TV -- from TiVo to Windows Media Center PCs to other PCs with video-recording software -- become more prevalent, the question of how to distribute all that video throughout the house looms for networking experts.

Big networking companies are already selling products designed to stream video wirelessly using 802.11g networks. But company officials acknowledge that system isn't perfect. If the signal must travel too far or deal with much interference from other networks or cordless phones, the video image can seriously degrade. Many of those same companies hope the solution will be faster Wi-Fi with better range.

But other experts argue that a real solution won't come from Wi-Fi, but rather from other systems that use wires you already have in your home -- either power lines or coaxial cables. They say Wi-Fi networks, no matter how fast, are inherently susceptible to interference from other wireless networks, devices like cordless phones, and even people blocking the wireless signal. While early adopters may be willing to deal with occasional video glitches, they say, customers who have spent thousands of dollars for HDTVs or pay a subscription for television service won't tolerate stuttering images. That's why TV manufacturers and companies that provide television service are looking hard at Wi-Fi's competitors.

What happened to HomePlug?

HomePlug 1.0, the standard for transmitting data along power lines, has been around for nearly three years, but seemed to have lost the network wars to Wi-Fi. Wi-Fi allows you to freely roam about with a laptop and still be connected to your network, while with HomePlug you must be plugged into an outlet to send or receive data, a major drawback.

But HomePlug advocates believe the technology may be victorious in the competition to carry video. A new standard, HomePlug AV, is due to be ratified in the first quarter of this year, and products using the technology will probably appear in early 2006. HomePlug AV will provide a theoretical throughput of 200 megabits per second, which would translate to a real-world speed of 70 to 120 mbps, according to Andy Melder, senior vice president of Intellon, which makes chips for HomePlug products.

By contrast, Belkin's Pre-N networking equipment, which uses MIMO, the latest Wi-Fi technology, delivered real-world throughputs of about 40 mbps at close range and much slower speeds at longer range in recent PC World tests.

Most experts say that transmitting a High Definition video signal requires speeds of at least 20 mbps.

Not only will HomePlug AV be faster, its advocates contend, it'll also be less susceptible to interference. Power lines have interference problems of their own from someone on the same circuit operating a device like a vacuum cleaner, drill, or halogen lamp. But HomePlug backers say they've found ways to work around those hindrances.

Both Samsung Electronics and Sharp participated in demonstrations at the 2005 International Consumer Electronics Show of early HomePlug AV devices used to feed HD content to the companies' televisions.

Back to basic cable

Another camp argues that the best wire for carrying video around your house is what probably delivers it now -- the coaxial cable used by cable television services. The Multimedia over Coax Alliance, which includes Cisco Systems, Comcast, EchoStar Communications (owner of Dish Network), Matsushita Electric Industrial's Panasonic division, Toshiba, and Radio Shack, is working on a networking specification that should be finished in the first or second quarter, says Ladd Wardani, MoCA's president. He expects MoCA-certified products will be available by this fall.

The theoretical maximum throughput for the coaxial networks will be 270 mbps, with an actual throughput of 100 to 135 mbps, Wardani says. Coaxial networks will be the least susceptible to interference, he says, because unlike Wi-Fi and power line nets, they operate on a protected spectrum. This means companies authorized to use that spectrum can complain to the U.S. Federal Communications Commission about any device that interferes. Wi-Fi or power line transmissions have no similar protections, because they use unlicensed spectrum, he says. No matter what backers do to improve Wi-Fi or powerline networks, "it doesn't remove the 'un' in unlicensed," Wardani says.

Big networking companies are putting bets on lots of the horses in this race. Linksys and Netgear, for instance, are both deploying new Wi-Fi technology and are also involved developing other standards.

And in the end, there likely won't be one winner, says Intellon's Melder. "The network of the future in the home is going to be a hybrid network," he says, with one system for video and another for data.

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Edward N. Albro

PC World
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