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Cable/Video

DOCSIS 4.0 Specs Near the Finish Line

A draft of the full DOCSIS 4.0 specs should be wrapped up by the end of January, with an anticipated release into the wild by the end of March, industry sources tell Light Reading.

That tracks well with a proclamation last month by Mariam Sorond, CableLabs's newly appointed chief research and development officer, that the D4.0 specs would be completed by "early 2020." CableLabs declined to comment further on specific DOCSIS 4.0-related timing.

Once the specs are done, chipmakers and other suppliers will have a clear green light to push further ahead with DOCSIS 4.0-based products that are already in development that will enable multi-gigabit symmetrical speeds along with low latency and advanced security capabilities.

A key piece of the DOCSIS 4.0 puzzle is the support of two technology options -- Full Duplex DOCSIS (FDX) and Extended Spectrum DOCSIS (ESD).

FDX, a technique of particular interest to Comcast, will allow upstream and downstream traffic to occupy the same block of spectrum, but require an "N+0" architecture whereby fiber is pulled closer to the premises. This would eliminate the need for powered amplifiers between the node and the home. By contrast, ESD, which appears to be advocated by most other cable operators, doesn't need N+0. ESD will keep upstream and downstream traffic separate while raising the spectrum ceiling on the hybrid fiber/coax (HFC) network initially to 1.8GHz. (Both DOCSIS 3.1 and FDX have a spectrum ceiling of 1.2GHz).

As the D4.0 specs are still being completed, some FDX-facing pieces of the specifications were published in the latter part of 2019. CableLabs and a group of industry engineers are in the final stages of developing the ESD portion of DOCSIS 4.0.

Supporting both FDX and ESD in the DOCSIS 4.0 specs will enable optionality and close the loop on what has been a point of contention with Comcast and other MSOs, but building it is proving to be a major complexity challenge for silicon suppliers such as Broadcom and Intel Corp., industry sources said.

Because they will support both FDX and ESD, those chips are expected to carry a premium price when compared to DOCSIS 3.1 silicon. Likewise, it's expected that the first generation of DOCSIS 4.0 chips won't be capable of supporting FDX and ESD concurrently, but instead will be able to support one mode or the other.

Looking beyond DOCSIS 4.0
Meanwhile, the cable industry is already starting to work on what will follow DOCSIS 4.0. That includes activity centered on a 3GHz downstream paired with a 1GHz upstream. Specs for 3GHz technology could take another 18 months to complete, but product based on it is probably at least five years out.

A big unknown is how this work will extend the life of widely deployed HFC networks based on the current rate of bandwidth demand and the adoption of various low-latency and data-intensive apps. Several such apps, like holodeck-like lightfield displays and home healthcare, are either emerging today or are on the longer-term horizon.

But the thinking is that that today's 1.2GHz DOCSIS 3.1 technology will buy the industry at least another three to five years. New 1.8GHz tech could extend that lifetime another 10 to 12 years, and 3GHz technology could provide enough runway for 20 to 25 years.

There's also work underway to help cable operators upgrade to these new platforms down the road without ripping up a bunch of plant or splicing in entirely new amplifier housings, connectors and other network components. The general idea being discussed centers on ensuring that the network infrastructure is 3GHz-ready through the use of housings that can support 1.2GHz and 1.8GHz technology but can also be retro-fitted with 3GHz components.

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— Jeff Baumgartner, Senior Editor, Light Reading

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