Last mile copper loops are largely considered a dead-end technology; fiber-to-the-home and coaxial cable systems offer much more headroom, so much so that even the recent National Broadband Plan lamented that most Americans would soon have only zero or one options for truly high-speed broadband. DSL users would remain stuck in the slow lane.
But DSL is not quite dead, and new research out of Bell Labs has resulted in a new speed record: 300Mbps.
So is DSL's future so bright that it needs to wear shades? We wouldn't invest in the shades just yet. This 300Mbps demo requires the DSL user to be within 400 meters of the local node; when the distance is extended to 1km, top speeds decline to 100Mbps. For those further away from the access point, as many in America are—my own home is twice that distance—these top speeds will be substantially lower.
Still, it's far better than the 6Mbps top speed AT&T offers me now (some AT&T U-verse customers can now get up to 24Mbps), but the new technology has other issues. Foremost among them: it requires the bonding of two DSL lines to each home.
This sort of "channel bonding" has long been used in DOCSIS cable systems and has been tested in the lab on DSL, but it never quite seems to make it to market in a big way.
To hit these high speeds, Bell Labs used channel bonding, vectoring (technology that avoids crosstalk interference between wires), and an analog "phantom mode." Phantom mode "involves the creation of a virtual or 'Phantom' channel that supplements the two physical wires that are the standard configuration for copper transmission lines," according to the lab.
Combine all these technologies together, use a pair of DSL lines, and test in the lab, and you get 300Mbps. The technology may be attractive to telcos who prefer to milk the value of their copper networks without springing for a more substantial fiber-optic upgrade.
Gee Rittenhouse, head of Research at Bell Labs, made this point, saying, "What makes DSL Phantom Mode such an important breakthrough is that it combines cutting edge technology with an attractive business model that will open up entirely new commercial opportunities for service providers, enabling them in particular, to offer the latest broadband IP-based services using existing network infrastructure."
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