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Ten suppliers hook into CableLabs' first DOCSIS 4.0 interop

May 28, 2023

Signaling a step toward full DOCSIS 4.0 certification testing, ten suppliers participated in the first CableLabs interop last month with cable modems, network gear and a prototype DOCSIS 4.0 test system, the organization announced this week.

CableLabs and its Kyrio subsidiary held the interop from July 17-21 at the CableLabs headquarters in Louisville, Colorado. Six DOCSIS 4.0-based cable modems (CMs) from four suppliers � a group that included Arcadyan, Sagemcom, Ubee and Vantiva � were part of the mix. It's likely that all of the modems involved were powered by new silicon from Broadcom. MaxLinear, a company that didn't participate in the July interop, is also working on D4.0 modem chipsets, with Hitron on board as one of its customer premises equipment (CPE) partners.

The modems involved in the interop interconnected to a handful of DOCSIS 3.1 cable modem termination systems (CMTSs) from Casa Systems, Cisco, CommScope, Harmonic and Vecima Networks. EPiDoX pitched in with a prototype DOCSIS 4.0 test system.

"The CMTS and CM suppliers iteratively paired CMs to CMTSs to test interoperability," Doug Jones, chief architect with CableLabs, explained in a blog post. "During this pairing and re-pairing, participants investigated the functionality and interoperability of the CM and CMTS equipment against the DOCSIS specification requirements. This process ensured all connectivity options between the CMs and the CMTSs were investigated."

Jones noted that "some issues" were discovered during the interop, giving everyone something to work on. "This is par for the course for a first interop, and it's exactly the reason we hold these events," he added.

First D4.0 modems connecting to D3.1 CMTSs

Connecting DOCSIS 3.1 CMTSs to new D4.0 modems will be important during the early days of the DOCSIS 4.0 era. It's expected that some operators will deploy DOCSIS 4.0 modems on their existing D3.1 networks to seed the market with new CPE as they prepare to make the leap to a full DOCSIS 4.0 network. That setup will also allow operators to squeeze out more capacity from the network by taking advantage of the extra OFDM (orthogonal frequency-division multiplexing) channels supported in the new modems that can also be supported by today's DOCSIS 3.1 CMTSs.

Some results from the first DOCSIS 4.0 interop come a few weeks after CableLabs and Kyrio announced that they were ready to start accepting D4.0-based cable modems for certification testing starting June 26. It's not clear whether any suppliers are ready to take that step, but last month's interop is another indicator that vendors are making progress toward that goal.

Those results also arrive as several North American cable operators, including Comcast, Charter Communications, Cox Communications, Rogers Communications and Cable One, start to upgrade their hybrid fiber/coax (HFC) networks.

As part of the new D4.0 testing process, CableLabs and Kyrio introduced two new elements of the program: success-based testing and 2-for-1 test results.

Success-based testing uses an iterative approach that permits devices to be updated as often as possible to achieve D4.0 certification without additional fees. Under the new 2-for-1 Test Results plan, D4.0-based modems will initially be tested for compliance with the DOCSIS 4.0 specs and interoperability with DOCSIS 3.1 networks to support some early deployments of the technology, and then be tested against D4.0-based CMTSs at a later time.

CableLabs is scheduled to host its next in-person DOCSIS 4.0 interop from August 14-17 in Louisville.

"We expect the same participants, and we'll revisit the scenarios from July and take a look at some new ones," Jones explained. "The goal is to keep pushing a more rigorous and deeper understanding of the DOCSIS 4.0 specifications and product maturity."

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— Jeff Baumgartner, Senior Editor, Light Reading