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DOCSIS

More spectrum the key to DOCSIS 4.0

DOCSIS 4.0, a new set of specs from CableLabs that represent the next chapter of the hybrid fiber/coax (HFC) network, promises to usher in higher levels of security and support apps that require super-low latencies, but boosting network capacity is the cornerstone.

"The key [for DOCSIS 4.0] really is spectrum," Doug Jones, principal architect at CableLabs, said last week during a "Live Learning" webinar hosted by Light Reading in conjunction with SCTE/ISBE focused on how operators can start to prepare for DOCSIS 4.0.

"With DOCSIS 4.0, spectrum is going to be a key that provides more capacity as well as more speed choices for consumers. With DOCSIS 4.0, we're really advancing the ball down the field toward 10G."

DOCSIS 4.0 intends to achieve that through a couple of different paths.

Full Duplex DOCSIS (FDX), a technology that started out as an annex to DOCSIS 3.1, supports a capacity upgrade to 1.2GHz, but adds in the ability to transmit upstream and downstream traffic on the same block of spectrum.

Extended Spectrum DOCSIS (ESD) currently supports up to 1.8GHz, and keeps the upstream and downstream traffic separated, with the option to dedicate a block of upstream in the range of 5MHz-684MHz.

For now, operators have been sizing up or starting to implement a "mid-split" upgrade that raises the upstream to 85MHz or a "high-split" that jumps it up to 204MHz.

When all the capabilities and spectrum are tied together, operators could use DOCSIS 4.0 to deliver capacity of up to 10 Gbit/s down and as much as 6 Gbit/s upstream.

"There's configurations where all of the spectrum on the coax can be allocated to broadband. That's a big deal," said Jones, noting that the amount of spectrum that can be used by DOCSIS 4.0 is roughly 200 times the amount that the single-channel DOCSIS 1.0 specs supported two decades ago.

Getting ready for D4.0
Though the first wave of DOCSIS 4.0 modems and gateways aren't expected until 2021 or beyond, operators and suppliers continue to concentrate on network planning ahead of these future upgrades.

As new systems and practices emerge for DOCSIS 4.0, they will need to live alongside the legacy systems.

That process will be aided by software defined networking and network virtualization alongside new automation capabilities, said Amol Chobe, principal solutions architect at Red Hat.

But "the cloud cannot solve every challenge," which is why operators will be relying on hybrid solutions during these transitions, Chobe said.

And the addition of new gobs of spectrum with DOCSIS 4.0 will also usher in some major changes coming to the physical plant, as fiber is deployed deeper into the network, said David Kozischeck, standards manager, global technology and industry standards at Corning.

One big change he sees coming is a surge in the number of wavelengths on the fiber, and the need to deploy more density into small spaces.

That boost in density, he said, could call on operators to deploy cabinets in the network as a demarcation point, that supports all of the new fiber nodes being deployed.

Another area cable operators will need to be wary of is power requirements, as capacity is built out to 1.2GHz and beyond, said Steve Condra, director, product management/engineering at Teleste Intercept.

Past spectrum upgrades involved much smaller increments than what's to come with DOCSIS 4.0, so managing the total composite power being put on the plant tied to this massive jump in network spectrum represents a major challenge ahead for operators, Condra said.

But the initial steps of DOCSIS 4.0 will likely involve the deployment of new passive devices that can accommodate these spectrum upgrades, said Neil Tang, president of Antronix.

"Right now is the time to start preparing your network, and typically passives are done first," Tang said.

3GHz on the horizon
DOCSIS 4.0 is still in the early development stages, but engineers are already noodling on standards that will support future HFC networks that are built out to 3GHz.

SCTE/ISBE launched a 3GHz task force more than a year ago and is making progress on a new 3GHz standards for network taps.

"There has never been an SCTE standard for the hardline tap, and now is the perfect time to create such a standard," said Dean Stoneback, senior director of engineering and standards at SCTE/ISBE.

"The cable operators have agreed that they want to only change tap housings one more time, giving them a runway for at least 30 years into the future."

He said there's a general desire to have a 3GHz backplate to these taps that can plug in various faceplates.

While the first wave of new faceplates will be for 1.2GHz or 1.8GHz, the backplate will be able to accommodate a 3GHz faceplate further down the road.

Stoneback said SCTE is also working on a similar standard for passives and is about to kick off a project for 1.8GHz actives that might include telemetry capabilities that could be supported by a Bluetooth low-energy interface or something similar to control it.

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— Jeff Baumgartner, Senior Editor, Light Reading

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