DOCSIS Technology Ramps Up Speed

DOCSIS® Technology Ramps Up Speed

Doug Jones
Principal Architect

Jun 22, 2023

Thanks to two recent innovations, DOCSIS technology is bringing more speed to the table. First, DOCSIS 3.1 cable modem termination systems (CMTSs) can now offer more DOCSIS channels than they did just a few years ago. Second, DOCSIS 4.0 cable modems (CMs) can take advantage of those extra channels to provide even faster speeds. DOCSIS is the gift that just keeps on giving.

DOCSIS Expansion

As you can see in the middle row of the figure below, the original DOCSIS 3.1 systems (circa 2016) supported about 5 Gbps of downstream speed. Technically speaking, this includes 2 orthogonal frequency-division multiplexing (OFDM) downstream channels and 32 single-carrier quadrature amplitude modulation (QAM) channels.

DOCSIS Graphic

As you see in the figure’s top row, upgraded DOCSIS 3.1 CMTSs (which are available now from multiple suppliers) can support a peak downstream speed of 8.8 Gbps by utilizing as many as 4 OFDM channels and 32 QAM channels.

Finally, illustrated in the figure’s bottom row, a DOCSIS 4.0 CM can use all the channels available with an upgraded DOCSIS 3.1 CMTS (actually more, as you’ll see in a moment). That means cable operators can almost double the downstream speed of their DOCSIS system by using a DOCSIS 4.0 CM on a DOCSIS 3.1 CMTS.

Faster Speeds

Confirming the strong performance of DOCSIS 4.0 technology, a recent press release about a live network field trial claimed that up to 15 Gbps of downstream speed is possible with a DOCSIS 4.0 CMTS and a DOCSIS 4.0 CM. This is possible because a DOCSIS 4.0 CMTS will provide even more capacity, supporting at least 6 and as many as 8 OFDM channels when complemented with an outside plant extending beyond 1.2GHz. This number is in line with DOCSIS 4.0 predictions of up to 16 Gbps of aggregate capacity.

How can one even quantify this explosion in speed? We’re talking about a leap from 5 Gbps to up to 15 Gbps downstream. This ensures support for evolving use cases that consume more and more downstream bandwidth. And once again, DOCSIS technology is up to the task, providing a useful roadmap of speed for the next generation of broadband applications.

How It’s Happening

To make this update to the DOCSIS 3.1 CMTS happen, suppliers are reusing a technology called channel bonding, which was added in the DOCSIS 3.0 specifications. The original DOCSIS 3.0 equipment supported 4 bonded downstream QAM channels (in North America, each 6 MHz wide), and the next generation of equipment supported 8, then 16, then 24 and finally 32 bonded downstream QAM channels.

DOCSIS 3.1 CMTSs are going through a similar evolution, evolving from bonding the original 2 OFDM channels (each up to 192 MHz wide) to 4 or more OFDM channels. And DOCSIS 4.0 CMs can use all these channels, which was part of the plan when the DOCSIS 4.0 specifications were developed. Channel bonding is a powerful tool—even more so now when using 192 MHz wide OFDM channels.

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. Operators can confidently deploy DOCSIS 4.0 CMs with enhanced service offerings as soon as they’re available, and then transition to DOCSIS 4.0 CMTSs as appropriate.

The Importance of Community

The DOCSIS supplier community deserves a shout-out! Once again, suppliers have provided cable operators with an appealing method to transition to the next generation of DOCSIS technology by getting started with DOCSIS 4.0 CMs on now familiar and near-ubiquitous DOCSIS 3.1 CMTSs. Suppliers and operators are collaborating on smart ways to transition to a DOCSIS 4.0 network; using a more capable DOCSIS 3.1 CMTS should be an attractive option.

CableLabs has been upgrading our labs to support this speed explosion. We’ve recently added new testing capabilities ranging from RF testing to enhanced traffic-generation capability to support the capabilities of DOCSIS 4.0 technology. Utilizing upgraded DOCSIS 3.1 CMTSs, CableLabs is very excited to work with DOCSIS 4.0 CMs to prove both the interoperability of the systems and the speeds that are possible.

DOCSIS® 4.0 Certification

To support the deployment of DOCSIS 4.0 CMs, CableLabs and Kyrio are kicking off the DOCSIS 4.0 Cable Modem Certification Program this summer. Starting June 26, modem suppliers can submit DOCSIS 4.0 modems for DOCSIS 4.0 certification testing, which will include testing with DOCSIS 3.1 infrastructure such as virtual CMTSs, Remote PHY Devices (RPDs) and Remote MACPHY Devices (RMDs).

Have any questions about DOCSIS 4.0 certification? You can find further details on Kyrio’s CableLabs Certification webpage (which includes a FAQ and guidelines).