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DOCSIS

It's go time for DOCSIS 4.0

CABLE NEXT-GEN TECHNOLOGIES & STRATEGIES – The full capabilities of DOCSIS 4.0 won't be ready to blossom for years, but it's important for cable operators to start planting the seeds now as new D4.0-capable network passives and amplifiers start coming on the scene, a panel of MSOs and tech vendors said.

Fueled by distributed access architectures and spectrum upgrades up to 1.8GHz, DOCSIS 4.0 will put widely deployed hybrid fiber-coax (HFC) networks in position to support capacities of up to 10 Gbit/s downstream and 5 Gbit/s in the return direction, roughly double what they can get with DOCSIS 3.1. That capacity boost will be paired with advanced security and low-latency capabilities.

But when cable operators will actually need DOCSIS 4.0 is a complicated answer and could vary by operator and market. So it behooves MSOs to start deploying certain 4.0-compatible pieces of the outside plant now in preparation for a later leap to a full, distributed DOCSIS 4.0-powered network even as silicon that will power other important elements of that platform – including remote PHY devices and customer premises equipment (CPE) – is still a few years out.

DOCSIS 3.1 should be able to carry cable operators through most of this decade, "but it will eventually run out of gas," Tom Cloonan, CTO-network solutions at CommScope, said on a DOCSIS 4.0 panel held Wednesday, Day 1 of the Light Reading-hosted two-day, virtual event: Cable Next-Gen Technologies & Strategies.

Jeff Finkelstein, executive director of advanced technologies at Cox Communications, agrees that DOCSIS 3.1's runway is still relatively long. He said D3.1 could give cable another five to seven years, or even ten years or more if it's for a network built to 1.2GHz paired with a "mid-split" that beefs up the swath of spectrum dedicated to the upstream from 5MHz-42MHz to 5MHz-85MHz.

Operators might regret doing some things on the cable network, Finkelstein said, "but adding spectrum is not one of those things."

But in the meantime, some of the pieces that will comprise a DOCSIS 4.0 network, such as those aforementioned passives and amps, could get deployed and sit ready for the day when there's need to light up the full, end-to-end D4.0 network, CommScope's Cloonan said.

And the time to get the ball rolling is pretty much here. Development of 4.0-compatible passives, for example, is "far underway" and the devices should be ready to ship later this year and into 2021, Neil Tang, president at Antronix, said.

Gating factors
However, "wholesale conversion" to DOCSIS 4.0 will be gated on silicon, Steve Condra, an exec with R&D and product management at Teleste Intercept, said.

Another gating factor for cable's embrace of DOCSIS 4.0 hinges on the rate of growth of bandwidth consumption, which has ticked up on residential networks during the pandemic, Tang pointed out, referencing a recent OpenVault study showing that users who consume at least 1 terabyte per month in Q2 2020 represented 8.7% of broadband customers measured, up 112% from the year-ago quarter.

The good news is that cable operators – as was the situation with previous generations of DOCSIS – should be able to deploy D4.0 rapidly, at scale and cost-effectively when it is needed because the platform still relies on existing infrastructure, JR Walden, CTO and SVP at Mediacom Communications, said. Other tools, such as FTTP in greenfields or to business locations, typically take longer to deploy than various iterations of DOCSIS, he said.

But precisely when cable operators will need DOCSIS 4.0 will be an informed guessing game. "The proper analysis will tell us when," Robin Lavoie, senior director, network evolution strategies with Canada's Cogeco, said.

Still, DOCSIS 4.0 could be of use today, at least in some narrow, targeted situations. "If it was in my tool bag today, there are scenarios I'd be running with this right now," Walden said.

HFC's paradox of choice
A challenge for operators will be how far and how fast to run with passives, amps and other products that will help to set the stage for a full-blown DOCSIS 4.0 network.

For example, if there's an opportunity to replace actives with 1.2GHz technology, but new 1.8GHz amps are on the near-term horizon, should an operator pull the trigger on 1.2GHz now or hold off a bit to wait for 1.8GHz?

"There will be a lot of timing elements that will challenge us," Walden said.

In that sense, the flexibility of DOCSIS and HFC – and the choices that are available for an operator to make during this transition – represents both an opportunity and an impediment, Condra said.

And there are other choices that cable operators might need to consider as they mull DOCSIS 4.0, a specification that supports both Full Duplex DOCSIS (FDX), a technology that allows upstream and downstream traffic to occupy the same block of spectrum, as well as Extended Spectrum DOCSIS (ESD), which continues to keep the upstream and downstream spectrum separate and dedicated.

Deploying FDX, which relies on a fiber deep/node+0 architecture, in a new-build situation is relatively straightforward, but could be more challenging and expensive on many existing HFC networks that have four to six amps between the home and the node, Jay Lee, chief technology and strategy officer, broadband access, at ATX Networks, explained in a keynote session focused on DOCSIS 4.0.

Another challenge is "psychological" because of possible doubts about whether these new technologies will do the job as promised, Finkelstein said. Those doubts, he believes, are unfounded as the cable industry ponders a 1.8GHz future.

"We know it works," Finkelstein said. "We need to get ourselves in that mindset [that] we can improve where things are on the cable plant."

The HFC network, he added, has "a long, useful life" ahead of it.

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— Jeff Baumgartner, Senior Editor, Light Reading

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