Is ADSL up to the task‾

11 Apr 2007
00:00

Carriers preparing for IPTV rollouts in Asia and the rest of the world are placing a large bet on ADSL and VDSL technologies to provide the bandwidth necessary for successful deployments. While DSL-based solutions often provide a more efficient and cost-effective alternative to full-scale fiber deployments, they too, present significant challenges for service providers.

Complexity, standards confusion and interoperability challenges are all combining to delay VDSL deployments in markets such as Asia and North America.

In a recent study, Vince Vittore, a senior analyst with Yankee Group, concluded that large-scale rollouts of VDSL.2 - a base technology for deploying triple-play services and IPTV - will be delayed until at least the middle of next year. Additionally, Vittore added, the lifespan of ADSL2+ (which is being used by some service providers as an interim step to VDSL) will likely be expanded because of continued VDSL snags.

'You've gotten delays in every flavor of DSL that has rolled out,' says Vittore. 'These are the types of delays you would get in any new technology.'

In his report, Vittore notes that the complexity of VDSL.2 is causing difficulties. The first VDSL.2 standard, ITU G.993, was approved in 2005 with the expectation that many telcos would deploy it by the end of last year. But that hasn't been the case. 'In an effort to push through the first of the two standards that make up VDSL.2 faster than normal, the ITU allowed multiple parties to contribute to the final standard,' notes Vittore. 'The result is a standard that has become highly complex and has several iterations.'

He isn't the only analyst with concerns. In a recent report about FTTP and VDSL, Analysys analyst Martin Scott warns that ADSL2+ lacks sufficient capability for IPTV when high-definition television is included in the equation. 'Real-life speeds of all DSL technologies can be as much as 40% lower at source than their theoretical maximum, and despite continuing improvements in digital processing, ADSL2 does not leave a lot of reliable bandwidth to play with over and above one HDTV stream,' he says. He adds that ADSL2+ can't cope adequately with HDTV bandwidth needs, so when it becomes the standard, VDSL.2 or fiber will need to be used.

Carrier confusion

All of this is causing confusion and some concern among carriers that have cast their lot with ADSL2+ and VDSL.2. Timeliness is a key issue for carriers in competitive markets such as North America. They are desperate to deploy IPTV as part of a triple-play solution to match aggressive cable competitors. For example, in the US, AT&T opted to proceed with a VDSL-based IPTV deployment because it was much less expensive (one-third to one-quarter the cost) than the estimated $25 billion being spent by rival Verizon to lay fiber to the curb in its service area.

But AT&T has significantly slowed its original deployment schedule and lags behind Verizon. In March, the company quietly admitted its broadband network will reach only eight million of the 18 million homes it originally promised to pass this year. The service is now available in only 13 markets in five states.

Vittore notes that AT&T is using compression technology to squeeze its IPTV signal to move it over ADSL2 lines until the VDSL.2 standard is finalized.

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