All Digital, All the Time

When will the day finally come when those analog channels finally can be taken off coaxial cable — freeing up scads of valuable bandwidth for new high-definition signals and other digital services?

For BendBroadband, a 34,000-subscriber cable operator in Portland, Ore., there's a date circled in red on the calendar: Dec. 31, 2008. In filings with the Federal Communications Commission, BendBroadband has committed itself to adopting a completely digital cable network by the end of 2008.

The operator claimed it needed a waiver to the FCC's July 1 ban on digital set-tops with integrated security features, because the Motorola DCT-700 boxes it buys for $79 each were less than half as expensive as models with separable security hardware.

And the DCT-700s, it said, are vital to its transition to a fully digital network. The FCC granted the request, on the condition that the operator actually does make the all-digital move without disrupting customers.

To get into a position to switch off the analog side of the house, BendBroadband first moved to digital simulcast.

With this technique, an operator delivers a full (or partial) digital channel lineup to digital cable customers, while simultaneously broadcasting the regular analog channels. For digital subscribers, that provides better picture quality and eliminates the need to use more expensive boxes that receive analog and digital channels.

Finally, digital simulcast can simplify the design of the metro-area transport network, by sending all the programming digitally then downconverting signals, reverting them to analog where necessary.

In 2005, BendBroadband became one of the first operators in the industry to deploy all-digital simulcast, a project it said cost about $750,000.

As BendBroadband CEO Amy Tykeson noted in the operator's waiver filing, “With simulcast, customers who have set-top boxes are able to receive 100% digital service, including superior picture quality, which in turn makes its digital product even more compelling for existing analog customers to buy.”

For other operators, eliminating analog channels — each consuming 10 times the bandwidth or more of their digital versions — will be a more gradual process. Many operators still count nearly half their customers on analog tiers.

But some cable companies think analog will stick around for a good, long time.

“I don't think analog will be going away completely,” said Pragash Pillai, vice president strategic engineering for Bresnan Communications, an operator with 300,000 customers in Colorado, Montana, Wyoming and Utah.

Not every customer wants a set-top box, Pillai pointed out. He suggested there will probably still be an analog tier years from now, though shrunk down from 80 channels today to perhaps 20 to 30.

Bresnan is still eyeing a predominantly digital future, though. For one thing, the FCC is mandating that broadcasters switch to digital over-the-air signals by February 2009, which should provide an additional push for cable's move to all-digital transmission.

For now, Bresnan is in the middle of rolling out simulcast in systems covering Montana and part of Wyoming. The area covers about 96,000 customers, with about 45% digital cable penetration.

The main benefit: All-digital set-tops are less expensive than hybrid analog/digital boxes. Bresnan, like BendBroadband, is looking to deploy the DCT-700 from Motorola. “For us, it's capital savings on the customer-premises equipment,” Pillai said. “The idea is to not buy any more analog boxes.”

Ray Bontempi, director of product management for Motorola's Connected Home Solutions division, said cutting costs is definitely one of the key drivers of the move to digital simulcast. “We see both large MSOs and smaller operators interested in moving to digital simulcast,” he said. “They make the same kind of economic decision.”

On the other hand, Cox Communications Northern Virginia's No. 1 goal for digital simulcast, initiated in mid-2006, was to deliver a sharper-looking picture. “There have been quite a few large-screen sets being purchased, and an analog signal doesn't provide the same quality,” system vice president of network development Darryl Ladd said.

Not all of Cox Northern Virginia's channel lineup is digital yet. About two dozen channels have yet to be transmitted in the digital tier, including the public, education and government (PEG) channels, PBS and HSN, based on past agreements specifying carriage only in an analog tier.

Ladd's goal is to have those carriage agreements updated, and complete the transition to an all-digital tier by the end of 2007. At that point the system's metro transport platform will be able to send the complete channel lineup digitally over Ciena's fiber-optic switching platform. Terayon decoders will reconvert channels back to analog in the system's six distribution hubs.

What about eliminating the analog tier? So far, Cox Northern Virginia, which has 250,000 subscribers, hasn't made any decisions. “We're not rushing to do that,” Ladd said.

More likely, he said, is that the analog tier will scaled back. For example, reclaiming just five analog channels — each occupying one quadrature amplitude modulation (QAM) channel — could yield capacity to deliver up to 80 new digital channels. That's because Cox Northern Virginia operates a 256-QAM network, which can carry as many as 16 digital channels per QAM.

But, Ladd said, “at that point it's more a question for the marketing and customer service groups, not the engineers.”

When digital simulcast first arrived on the scene a few years ago, most operators initially moved only part of the analog tier into the digital tier, said Ramin Farassat, vice president of technical marketing at video-processing equipment vendor RGB Networks. That's because the first generation of edge encoders were expensive and had comparatively low density.

“What happened is the cost has gotten to the point where it's become cost-effective to do the full 70 to 80 analog channels now,” Farassat said.

In a digital simulcast architecture today, the digital-to-analog conversion is typically performed in a distribution hub. That means spectrum in the last mile of coaxial cable must still be allocated for the fat analog tier — up to 500 Megahertz, or more than half the capacity of an 870-MHz system.

Now, what if the digital/analog decoding were done right in the customer's home? That would effectively let an operator turn up an all-digital network while retaining an “analog” tier.

The high processing power needed to do this has made such solutions too expensive for mass deployment. But in November, startup BroadLogic Network Technologies claimed it cracked this code with a high-efficiency chip set it says will handle digital-to-analog conversion of 80 channels. A BroadLogic-based device, perhaps deployed on the side of a house, would cost no more than two digital set-tops, the company said.

Still, the BroadLogic technology is at least a year away from commercial deployment. Jeff Huppertz, the company's vice president of marketing and business development, said BroadLogic has received field-trial commitments from 3 of the top 10 cable operators, with commercial deployments targeted for 2008.

And RGB's Farassat was skeptical the concept would become feasible. “I still haven't seen a cost-effective way of demodulating 80 channels,” he said.

Motorola, meanwhile, is looking to develop products using BroadLogic's or silicon from other vendors. But Bontempi acknowledged at-the-home video decoders haven't been tested in the real world.

“It's good technology,” he said. “But it's really a matter of letting the marketplace to decide how to go, because to take advantage of that technology you need to implement it across the entire network.”