Cable ops reveal game plan for DOCSIS 3.1

The cable industry has a good thing going with the combination of its hybrid fiber/coax (HFC) network infrastructure and Data Over Cable Service Interface Specifications (DOCSIS) high-speed data platform, so it was only a slight surprise that a panel of high-powered industry executivesThursday laid out a DOCSIS 3.1 plan, even as DOCSIS 3.0 has just barely begun.

After all, as one observer pointed out, cable can use what it has because it works, and it's not being threatened by any large-scale fiber-to-the-premises (FTTP) competition.

It was thought at one point that cable would be forced to move off its successful, albeit long-in-the-tooth HFC/DOCSIS combo and move into deep fiber, but with the industry's biggest player, Verizon FiOS, halting any further expansion of its FTTH efforts, cable has some room--and some time--to wring just a little more out of DOCSIS before it has to bite the inevitable bullet and deploy fiber all the way to the premise.

"HFC has scaled exceptionally well and we expect it will keep up well for the next decade or two," said Dan Rice, vice president of access technologies for CableLabs, speaking at and moderating a tech exec-studded panel at the SCTE Cable Tec Expo Thursday that laid out the reasons why the cable industry is moving to DOCSIS 3.1.

First and foremost, it's happening because the cable guys want to stay ahead of what they know is consumer demand by delivering a minimum of 10 Gbps throughput downstream and 1 Gbps up.

Most importantly, the migration is happening because the industry looked around and saw no one there to challenge its HFC infrastructure and, since DOCSIS has led cable from a broadcast video player to a high-speed interactive juggernaut delivering a triple play of voice, video and data products, "we want to work on the existing HFC plant," said Matt Schmitt, director of DOCSIS specifications for CableLabs, promising that the new specification will entail "zero plant investment."

"Plant changes are potential enablers for other things," Schmitt said. "You don't have to change your plant to deploy DOCSIS 3.1."

There are some changes that the new spec will require. It will use orthogonal frequency-division multiplexing (OFDM) to wring a minimum of 500 MHz of space on a typical 1GHz or less cable plant and it could--probably will--jack up the QAM structure from 256 QAM to a peak of 4096 QAM "and maybe even beyond that," Schmitt said. Finally, there will be new forward error correction (FEC) and probably some use of Low Density Parity Check (LDPC) to keep all that data running smoothly.

In all, Schmitt said, DOCSIS 3.1 is "trying to take the long view and think about where we're going to be in the future."

While 3.1 promises to be more powerful and less expensive than 3.0 and the aim is to avoid changing the plant, it doesn't obviate the need to buy new equipment when, if Schmitt is correct, it becomes available in 2014.

"It's not like we're going to buy less equipment; we're going to buy more efficient equipment," said Jorge Salinger, vice president of access architecture for Comcast. "It will never be a migration; it's growth. We are constantly adding equipment because of growth."

Related articles:
SCTE creates DOCSIS 3.1 working group
Next up, DOCSIS 3.1