VDSL - Closer to reality but far from convincing
Michelle Donegan
26 November 2001
Telcos think that very high bitrate DSL will help them compete with cable operators, but others have yet to be persuaded.
<<another flavor of DSL, when are they going to accept defeat?>>
A high-level industry working group is putting the finishing touches on a digital subscriber line implementation specification, which telecoms network operators hope will outclass cable technology in handling multimedia services.
Many telcos believe very high data rate digital subscriber lines (VDSL) will be the technology that stops their customers from defecting to cable operators, which at the moment can more easily offer the consumer broadband bundle of high-speed Internet, video and voice services.
But some analysts say an asymmetrical digital subscriber line (ADSL), with a downstream speed of 2.3 Megabits per second, is perfectly adequate to deliver near-broadcast quality TV channels, which they say is all that is required for video-on-demand (VOD) services.
"Telcos could asphyxiate if they hold their breath waiting for VDSL," said Tim Johnson, DSL industry consultant at Ovum Ltd., of London. "It's not just the standards question, but the whole business of adding a new layer of fiber to the network to support curbside cabinets. I think it makes sense to use ADSL for what ... it was originally designed for: video-on-demand."
The FS-VDSL Committee will complete its draft specifications for full service, very high bitrate DSL deployments at its plenary meeting in Rome next month. This could spur operators into rolling out VDSL technology in the second half of 2002.
"There's a commercial drive in big telcos and a desire to fight back against cable operators," said David Greggains, a director of the DSL Forum and director of Gorham & Partners management consultants, of London.
"And there really is only one way to do it and that's with VDSL."
Specs will spur growth
Launched in July last year, the FS-VDSL Committee is developing end-to-end implementation specifications for VDSL (CWI, 11 September 2000, p.18). The group works out issues like how much bandwidth should be allocated to each video stream, or how multiple video streams should be distributed inside a home to different TVs, i.e., via one box or several.
"If we can issue our specification on time, we hope that we'll provide a fillip to the industry to deploy VDSL. This could boost recovery," said Don Clarke, head of VDSL deployment at BT Exact and technical director of the FS-VDSL Committee.
VDSL standardization has been controversial from the start, with long-running disputes over the frequency plan and the line code. But the FS-VDSL Committee complements the work of standards bodies by working out specifications for implementation.
"There was a realization that you have to have an end-to-end specification from content aggregation right through to the TV in the home, plus certain operational support plans as well," said Clarke.
VDSL can deliver 26 Megabits per second over 4,000 feet of copper wire, which will allow for two to three video streams, plus data and voice.
The data rates are much higher than ADSL, but the distances are shorter.
This is why operators will need to build fiber out to street cabinets and then run VDSL over copper into homes. It can be asymmetrical or symmetrical, but early deployments are likely to be asymmetrical with a much slower upstream. "It's a question of getting the economics right for getting the fiber close enough to the homes," said Greggains, of Gorham & Partners.
Analysts don't expect significant VDSL deployments for some time. "It will probably be a couple of years before anything gets started with VDSL," said Beth Gage, vice president of consulting at Telechoice Inc., of Denver.
Meanwhile, operators are running VDSL trials (see box). Qwest in the United States leads the world with its VDSL trial in Phoenix, Arizona, and Highlands Ranch, Colorado. Qwest does not have plans yet for a broader rollout of VDSL. "We're currently evaluating the customer demand, costs of deployment, support and ongoing viability of the service," said a Qwest spokeswoman.
In Stavanger, Norway, Telenor has been offering 26 Mbps to 750 homes in a trial since November 2000. "We don't believe we can compete with satellite operators with lower bit rates," said Leif Ims, a project director and head of VDSL at Telenor, of Oslo. "Some operators will be disappointed (by) doing (VOD and broadcast TV) over ADSL."
Telecom Italia has also begun a small trial of VDSL in Turin, Milan and Rome.
VDSL TRIALS WORLDWIDE
- Bell Canada VDSL trial in luxury apartment building in Toronto; around 140 participants
- Qwest Limited deployments of VDSL to 50,000 subscribers in Phoenix, Arizona, and Highlands Ranch, Colorado. Service costs from $30-$79 per month for packages ranging from video channels to Internet access.
- Telecom Italia VDSL trial to about 100 people in Turin, Milan and Rome.
- Telenor VDSL trial with 750 homes in Stavanger, offering 26 Mbps. Also trial in Oslo offering 10 Mbps.
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