CARRIERS GET THEIR WISHES: ITU APPROVES VDSL2 STANDARD

SBC Communications has made no secret of its desire to begin testing VDSL2 equipment as soon as possible. That day is now significantly closer after the International Telecommunications Union's grueling two-week meeting in Geneva, Switzerland, which concluded with the ITU announcing a finalized agreement on a VDSL2 standard.

The standard, which was accelerated at the urging of several large carriers, provides for a number of bandwidth options. At its highest level, the standard will allow carriers to transmit data at 100 Mb/s in both the upstream and downstream paths over relatively short copper loops. From a more practical perspective, particularly in the North American market, the standard provides for 30 Mb/s at 6000 feet.

“We worked a lot of 12-hour days, and there were a couple of sessions that went until three in the morning,” Ed Eckert, director of strategic standards for chip vendor Ikanos, which announced a pre-standard VDSL2 chip set late last year.

The result, like most standards, includes a little something for everyone, he said. As expected, it will include three profiles for chip vendors to build to: one at 8 MHz, one at 12 MHz and one at 30 MHz ( mostly for Asia and some select European markets).

SBC has specified that it wants equipment that will operate in the 12 MHz profile and expects to provide for 30 Mb/s at 6000 feet. “We are absolutely putting out a requirement that we go no higher than 12 MHz,” said Gene Edmon, executive director of broadband for SBC Labs, before the Geneva meeting.

At that level, the company will be able to provide a true triple-play package of one high-definition video stream, two standard-definition video streams and two voice-over-IP channels and still have enough left over for high-speed Internet access, according to Ken Madison, senior product marketing manager for Centillium. The carrier also included a bit of a “fudge factor” in its requirements, knowing that all copper plant isn't equal.

Despite agreement by most sectors of the industry that the VDSL2 standardization will go a long way toward making it a widely deployed technology, there are several hurdles. Key among them is how the standard will be interpreted by chip vendors and others.

Just days after the official ITU announcement, a spokesperson for Infineon said the company has developed a chipset that complies with the standard. “It's sampling now, and we expect to have it in production quantities in the third quarter of the calendar year,” the spokesperson said.

Making the standard work in a real-world environment will take time, though, Madison said.

“It has become a standard that means everything to everyone,” he said. “The question is how the standards are going to be translated.”

Eckert said he wasn't surprised by a competitor timing its announcement to be immediately after the ITU meeting, but getting the chipsets functional is another thing. Ikanos is one of only a small group of VDSL chip vendors

“It's going to take six to twelve months from the time chipsets are out that they're going to get this right,” he said. “We know that from experience.”

Beyond implementation, carriers also will demand interoperability, Eckert said. Eckert is editor of the VDSL2 interoperability group within the DSL Forum and expects that group to have its first plugfest by the end of the year and an interoperability document out by September.

“I'm really hoping we don't go down the same path that ADSL2 and ADSL2+ have gone down because that's been an interoperability nightmare,” he said. “There were a lot of bells and whistles in ADSL2 and 2+ that frankly didn't get used in the field.”

VDSL2 PROFILES

Band	Best case throughput
8 MHz	20-30 Mb/s downloads between 2500-4000 feet
12 MHz	30 Mb/s at 9000 feet
30 MHz	100 Mb/s symmetric at 700 feet
Sources: Ikanos and Centillium