Ushering in what will become the next generation of the cable industry's IP platform, CableLabs announced it has released the specifications for DOCSIS 4.0, a technology that will put the industry on a path toward speeds of 10 Gbit/s downstream and up to 6 Gbit/s in the upstream.

CableLabs said the raw speeds enabled by DOCSIS 4.0 on widely deployed hybrid fiber/coax (HFC) networks represent a doubling of the max downstream available via DOCSIS 3.1 and a quadrupling of the upstream capacity of D3.1. DOCSIS 4.0 also covers advanced capabilities such as enhanced security and low latency.

DOCSIS 4.0, in the works since August 2016, will also support both Full Duplex DOCSIS (FDX) and Extended Spectrum DOCSIS (ESD). FDX, a technology favored by Comcast, will allow both upstream and downstream traffic to occupy the same block of spectrum. ESD, by comparison, will keep upstream and downstream traffic separate, as it is today, but will also raise the spectrum ceiling on hybrid fiber/coax (HFC) to 1.8GHz, up from about 1.2GHz today in the most advanced HFC networks. Future versions of the DOCSIS specs could support spectrum up to 3GHz.

The new DOCSIS 4.0 specs provide the technical guidance needed for chipmakers and suppliers of network gear and DOCSIS modems and gateways to push ahead with product development and, eventually, production.

Two big questions are when will DOCSIS 4.0-based products hit the market and when will cable operators actually need this next wave of technology to stay a step ahead of network demands. CableLabs won't speculate on when it will be ready to start DOCSIS 4.0 product testing, let alone estimate when the first D4.0 products will be ready for trials and commercial deployments. But cable engineers and other industry insiders expect the DOCSIS 4.0 era to take several years to unfold.

According to industry sources familiar with product development plans, DOCSIS 4.0-based passive network devices could emerge later this year, with active network elements to follow sometime in 2021. DOCSIS 4.0-capable remote PHY and remote MACPHY devices for emerging distributed access architectures could start to surface in 2022 or 2023. DOCSIS 4.0 customer premises devices (CPE) will likely take longer and show up no earlier than 2023, according to industry sources.

Another determining variable on the CPE side will be Broadcom's and Intel Corp.'s appetite to make DOCSIS 4.0 silicon without major commitments from cable operators. It's also not known if Intel will stay in this market long term as it has been shopping its home connectivity unit, which makes chips for DOCSIS modems and gateways.

"We're talking through strategies" for DOCSIS 4.0 CPE, an industry source said, noting that there are discussions underway about how existing silicon could be used in a way that would allow a block of OFDM spectrum used today for DOCSIS 3.1 to be "upconverted" above 1.2GHz.

Time is on cable's side
But there's no big rush to get DOCSIS 4.0 deployed, as DOCSIS 3.1 has already given cable operators a way to offer gigabit speeds, at least in the downstream. The near-term pressure is on cable's relatively feeble upstream path, which will be expanded in upcoming years through mid-splits that raise the usable upstream spectrum from today's 5MHz-42MHz (for North America) and 5MHz-65MHz (for Europe) up to a 85MHz ceiling. A so-called "high-split" could raise the upstream ceiling to 204MHz, while "ultra high-splits" envision the upstream path going as high as 684MHz.

All that aside, engineers contacted by Light Reading estimate that today's DOCSIS 3.1 technology provides at least four more years of runway, giving operators plenty of time to seed the network for DOCSIS 4.0 and be ready to go once D4.0 CPE becomes available.

The good news is that chipmakers and vendors won't be pursuing DOCSIS 4.0 from a standing start. All the traditional DOCSIS tech players have been involved with spec development from the get-go.

DOCSIS 4.0, industry insiders say, could provide another five to six years of runway, and a future version with a 3GHz ceiling could provide several years more – all postponing the need for most MSOs to go with expensive fiber-to-the-premises upgrades. Among domestic cable ops, an exception to this thinking is Altice USA, which is deploying DOCSIS 3.1 in pockets as it pursues an ambitious initiative to roll out FTTP upgrades in its Optimum (former Cablevision Systems) footprint in New York, New Jersey and Connecticut.

While it's impossible to know how changes in data demands and how new bandwidth-eating apps and services will alter the curve, there is hope that a fully fledged DOCSIS 4.0 platform, with an eye toward future iterations that support 3GHz, could give cable plenty of pop for possibly two decades. Consider today's news just one early but important step along that path.

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— Jeff Baumgartner, Senior Editor, Light Reading