New ITU standard boosts speed of DSL

VDSL2 can deliver as much as 100Mbit/sec., both upstream and downstream

Faster broadband came closer to reality Friday with completion of the latest International Telecommunication Union (ITU) standard for Digital Subscriber Line (DSL) service, which is already in the playbooks of two major U.S. carriers.

The specification, called VDSL2 (for very high bit-rate DSL 2), can deliver as much as 100Mbit/sec., both upstream and downstream, according to an ITU statement. That bandwidth, many times current DSL speeds of just a few megabits per second or less, could handily deliver voice calls, videoconferencing, high-definition TV and video on demand over existing copper phone lines, according to the standards body, an agency of the United Nations.

VDSL2 will play a key role in faster DSL services coming from major U.S. carriers over the next few years, although they have different expectations as to when gear using the standard will be available.

The new standard is at the center of strategies at U.S. regional carriers SBC Communications Inc. and BellSouth Corp. Rather than build out all-fiber networks as Verizon Communications Inc. is planning to do, they intend to build a fiber infrastructure down customers' streets or to a neighborhood node and use copper wire "loops" to homes and businesses. VDSL2 is intended to make a fat pipe out of those copper wires.

BellSouth plans to announce details next week of plans for its next generation of DSL, according to spokesman Brent Fowler.

"We are planning our network transformation around VDSL2," Fowler said. Over time, it will lead from current offerings of 1.5Mbit/sec. (3Mbit/sec. in some areas) to as much as 100Mbit/sec. downstream, he said. VDSL2 gear, which BellSouth expects to become available over the next few years, will be deployed as the final phase of the project. Before that, the carrier will roll out ADSL2 (Asymmetric DSL 2) to deliver as much as 24Mbit/sec.

VDSL2 gains speed on earlier technologies as the copper loop gets shorter, Fowler said. On a 5,000-foot copper loop, it delivers about 12Mbit/sec., the same speed as ADSL2. But at just 500 feet, VDSL2 can provide 80Mbit to 100Mbit/sec., compared with ADSL2's 24Mbit/sec., he said.

BellSouth's strategy is to bring fiber to the curb in front of a subscriber's home, so the average copper segment will be about 250 feet. Most customers will get service between 50Mbit and 100Mbit/sec., he said.

SBC plans to speed up its broadband offerings by bringing fiber to neighborhood nodes and using VDSL2 over the copper loops, most of which will be about 2,500 feet, said company spokesman Michael Coe. Subscribers will get at least 20Mbit/sec. and in some cases much more, depending on distance from the node and other factors, he said. The rollout, called Project Lightspeed, will begin later this year and should become available to 17 million homes and businesses over the next three years, he said.

Qwest Communications International Inc. is also interested in VDSL2, but it's waiting to implement the service until vendors ship network equipment that complies with it, a company spokeswoman said. The company wouldn't speculate on how much bandwidth a Qwest VDSL2 network would provide, she said.

By contrast, Verizon's strategy is to deploy fiber to the curb and then lay more fiber all the way to the home or office for customers who sign up for its Fios high-speed service. The carrier currently offers services with 5Mbit/sec. downstream (2Mbit/sec. upstream), 15Mbit/sec. downstream (2Mbit/sec. upstream) and 30Mbit/sec. downstream (5Mbit/sec. upstream), said spokesman Mark Marchand. But the fiber infrastructure could deliver as much as 100Mbit/sec. of downstream data in addition to hundreds of channels of video, he said.


Copyright © 2005 IDG Communications, Inc.

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