Cable modem makers almost ready to take the DOCSIS 4.0 test

A webinar with manufacturers and cable operators hosted by CableLabs about the new DOCSIS 4.0 certification testing process revealed that a few vendors expect to be ready to submit modems and gateways as early as the third quarter of 2023.

In a poll to an unshared number of DOCSIS modem manufacturers, 5% said they expect to be ready to submit their first cable modem for DOCSIS certification sometime in the third quarter of 2023. A larger group representing 57% of votes said they expect to be ready by the fourth quarter of 2023. Others shared they plan to be ready by sometime in 2024 or later.

The poll is, of course, an inexact measure of vendor readiness for D4.0 testing. But it does shed some light on their status for DOCSIS 4.0, a new set of CableLabs specs that will enable symmetrical multi-gigabit speeds alongside enhanced security and low-latency capabilities.

CableLabs ready to run DOCSIS 4.0 tests

CableLabs recently announced that it would be ready to start DOCSIS 4.0 certification testing on customer premises equipment (CPE) starting June 26.

No suppliers that are using Broadcom's D4.0 silicon have said publicly if they expected to be ready by June 26. Hitron, a company that is developing D4.0 products powered by MaxLinear silicon, told Light Reading it planned to be ready to submit products for DOCSIS 4.0 certification testing by the first half of 2024.

CableLabs held a Zoom call today to provide more detail on its new DOCSIS 4.0 certification program and to take questions from manufacturers and cable operators.

It's up to vendors to determine when they are ready for D4.0 testing, but the goal of the certification program is to help operators and their suppliers deploy those new modems "at scale as soon as possible," Matt Schmitt, principal architect at the wired group at CableLabs, explained on today's webinar.

Schmitt also elaborated on some nuances tied to the D4.0 program. A new two-for-one testing program will enable modem makers to initially test their gear against DOCSIS 3.0 and DOCSIS 3.1 cable modem termination systems (CMTSs) and to later test against a new breed of D4.0-based network gear.

When a CPE manufacturer successfully tests a D4.0 modem against a DOCSIS 3.1 CMTS, the product will be deemed "verified for interoperability" by CableLabs. When that modem tests successfully against a DOCSIS 4.0 CMTS, the product will be added to CableLabs' list of certified modems.

The net effect for a supplier is a single submission with two published results, Schmitt said.

It's too early to know how long it will take for suppliers to complete either the phase I or phase II testing for DOCSIS 4.0. But CableLabs has invested in new tools and capabilities to accelerate its testing capabilities for D4.0, Schmitt said.

Aside from official D4.0 certification testing, CableLabs is targeting the week of July 17 for its first DOCSIS 4.0 interoperability event. It's not mandatory for suppliers, but it will give CableLabs and manufacturers an opportunity to interpret some of the new testing parameters and iron out possible ambiguities.

Meshing DOCSIS 3.1 and DOCSIS 4.0

The DOCSIS 3.1 testing component is key in a couple of ways. In addition to showing backwards-compatibility, testing a D4.0 modem against a D3.1 CMTS fits in with a way operators might deploy those new modems.

Some operators are contemplating the operation of D4.0 modems on upgraded DOCSIS 3.1 CMTSs that are capable of supporting additional blocks of OFDM (orthogonal frequency-division multiplexing) spectrum. Today's D3.1 modems can support two OFDM blocks (with each up to 192MHz wide). But D4.0 modems can support four OFDM blocks or more, possibly putting cable operators in position to use those new modems to deliver faster speeds on DOCSIS 3.1 networks that have been upgraded to 1.2GHz.

CableLabs detailed that scenario in this blog post by Principal Architect Doug Jones.

While original DOCSIS 3.1 systems supported about 5 Gbit/s downstream by combining two OFDM downstream blocks and 32 single-carrier QAM channels (using DOCSIS 3.0 channel bonding), upgraded D3.1 CMTSs can push that figure to 8.8 Gbit/s by combining up to four OFDM blocks and 32 QAM channels. But to access all of that spectrum and achieve such lofty speeds, a DOCSIS 4.0 modem is required. Here's how Jones and CableLabs illustrate these potential scenarios.

Click here for a larger version of this image.
(Source: CableLabs)

"Utilizing the ability to bond additional OFDM channels when operating a DOCSIS 4.0 CM on a DOCSIS 3.1 CMTS not only supports more capacity, and therefore enhanced benefits for consumers; it also gets those benefits to consumers much sooner," Jones explained.

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— Jeff Baumgartner, Senior Editor, Light Reading