Cable operators see surge in network upgrade options

Cable ops can squeeze more out of DOCSIS 3.1, go for DOCSIS 4.0, wait for what follows DOCSIS 4.0 or bite the bullet with FTTP. Options abound, but the situation could put more stress on the already challenged cable tech sector.

Jeff Baumgartner, Senior Editor

July 9, 2024

8 Min Read
lank signpost multiple directions against a blue sky
(Source: incamerastock/Alamy Stock Photo)

The cable industry isn't facing a simple crossroads regarding the future of their widely deployed hybrid fiber/coax (HFC) networks. Instead, operators have a multitude of paths and options to choose from.

Some might stick with DOCSIS 3.1 and beef up the upstream with "mid-split" or "high-split" upgrades that allocate more spectrum to the upstream path. Others could take a closer look at an upgraded version of D3.1 (call it DOCSIS+ or "extended" DOCSIS 3.1) that can boost the performance of the downstream while potentially putting off an upgrade to a distributed access architecture (DAA). Additional options include going for a full DOCSIS 4.0 upgrade paired with DAA or simply shifting investments into fiber-to-the-premises (FTTP) overlays and upgrades.

Looking even further out, a small group of operators and suppliers is examining how to juice capacity by operating 5G signals on HFC in spectrum up to 4GHz or 5GHz. Also on the table is how to extend DOCSIS's spectrum ceiling to 3GHz – perhaps ushering in what might become DOCSIS 4.1 or DOCSIS 5.0.

Picking a horse

Some operators have already placed their bets. Comcast is focusing on the Full Duplex (FDX) flavor of DOCSIS 4.0, while Altice USA continues to push an FTTP overlay in its footprint in the Northeast and DOCSIS 3.1 upgrades for systems in more rural areas in the West.

Related:Cable's secretive 'NRoC' project explores way to run 5G on HFC

It may be possible for operators to mix and match strategies depending on factors such as local competition or the condition of the legacy HFC plant.

Notably, Charter Communications is using a three-phased approach that involves an upgrade to 1.2GHz without DAA, an upgrade to 1.2GHz with DAA and a virtual cable modem termination, and a full DOCSIS 4.0 upgrade. All three enable the company to deliver multi-gigabit speeds downstream and at least 1 Gbit/s upstream.

Still, some cable engineering execs believe operators will need to pick one horse and ride it.

"You can't do two to three strategies. It's uneconomical. You have to pick one," said one engineer who is familiar with the available paths forward for HFC.

"None of this [optionality] is bad, but we have to settle on something," said another cable engineering exec. "At some point you have to put your pencils down and buy and deploy something."

Here's an illustrative review of the top options available to cable operators today, and a pair of options that might serve them further down the road.

DOCSIS 3.1 upgrades

This option comes under many non-official labels: DOCSIS 3.1+, DOCSIS 3.1 "stretch" and DOCSIS 3.1E ("E" stands for "extended" or "enhanced"), among them. The idea is to boost downstream speeds by taking advantage of new DOCSIS 3.1 and DOCSIS 4.0 modems that can support four to five orthogonal frequency-division multiplexing (OFDM) channels, compared to the two OFDM channels supported by the current generation of DOCSIS 3.1 devices.

Related:Cable ops are lab-testing 'enhanced' DOCSIS 3.1, CommScope says

The good news is the market will have access to a pair of silicon options for the modem piece: MaxLinear's new Puma 8 (running in D3.1 mode) and a new chip from Broadcom (the BCM3392) that the company has yet to officially announce. Industry sources tell Light Reading that access to Broadcom's BCM3392 won't be limited by the expensive joint development agreements (JDAs) that currently govern access to Broadcom's new DOCSIS 4.0 chips.

Meanwhile, it's possible that this approach could be supported in legacy cable modem termination systems (CMTS) outfitted with new software and not require a DAA upgrade. CommScope recently announced that cable operators are starting to run lab tests of DOCSIS 3.1+ underpinned by a new release of software for the E6000, the company's chassis-based CMTS.

The upgrade option is attractive to small and midsized operators, but they've yet to announce commitments to it.

Related:How Broadcom and MaxLinear will push the limits of DOCSIS 3.1

GCI has requested the D3.1+ license to run lab tests of the E6000 operating more than two OFDM blocks, said Erik Kuhlman, senior director of engineering and architecture at GCI, in an email exchange.

"While we are interested in the lab results, our practical experience with deploying high-split RPDs [remote PHY devices] on the E6k in a hybrid DAA/analog configuration has been less than ideal," Kuhlman explained. "This has led us to pause our current DAA deployment strategy and transition to dedicated virtual cores going forward. As a result, E6k support of D3.1+ is not a high priority for GCI at this time."


The DOCSIS 4.0 era is underway, paving the way for cable operators to deliver symmetrical multi-gigabit speeds, lower latencies and enhanced security on their HFC networks. A big prerequisite is DAA.

But D4.0 is fragmented in that it supports two options. FDX, a version favored by Comcast, envisions plant built to 1.2GHz and the use of an FDX band that allows upstream and downstream traffic to occupy the same block of spectrum. The other option, Extended Spectrum DOCSIS (ESD), would extend plant to 1.8GHz and continue to keep upstream and downstream traffic operating in separate spectrum.

MaxLinear's Puma 8 chip supports the ESD option. Broadcom, in conjunction with Comcast, has developed "unified" chips for modems, amps and nodes that support both FDX and ESD. However, access to Broadcom's latest silicon is currently limited to a handful of operators that have signed JDAs with Broadcom: Comcast, Charter, Cox Communications and Rogers Communications.

Deployments are in the very early stages, led by Comcast, which has begun to offer D4.0-fueled services in parts of Atlanta, Colorado Springs and Philadelphia, with Seattle among the markets on deck.

CableLabs opened DOCSIS 4.0 certification in mid-2023, but as of this writing no products have been given the official stamp of approval.


Fiber-to-the-premises (FTTP) is now the clear choice for cable operators in greenfield scenarios, including edge-outs to areas adjacent to existing HFC and in new, government subsidized buildout markets.

But FTTP is also an option in existing networks for certain operators. Altice USA, for example, is leaning hard on that approach in its footprint in New York, New Jersey and Connecticut. Meanwhile, Virgin Media O2 is in the process of upgrading its entire UK network to FTTP even as it continues to operate its legacy DOCSIS network.

While DOCSIS still has plenty of gas left in the tank, some cable industry vets believe that fiber will eventually win out in the wireline world. Therefore, they believe cable operators should take a "fiber first" approach to their network strategies.

"I think a mistake would be to put every single penny we have on upgrading the cable network to the latest version of DOCSIS and chase it," John Chapman, a former Cisco exec and DOCSIS pioneer, said during last month's Cable Next-Gen Europe 2024 hosted by Light Reading.

Chapman suggested that operators should consider upgrading a small portion of their HFC networks each year.


Industry players are also exploring a couple of other options that could either complement DOCSIS 4.0 or go beyond it.

Charter, CableLabs, Rogers and Technetix, for example, are looking into a way to overlay 5G signals on HFC at loftier frequencies – up to 4GHZ or 5GHz. That option, currently referred to as NRoC (for Next-Gen Radio over Coax or Next-Gen Radio over Cable), would see operators continue to operate DOCSIS up to 1.2GHz, and then use 5G to deliver services above that part of the spectrum.

Notably, NRoC could put cable in position to take advantage of global 5G standards that are supported by a massive ecosystem of silicon providers.

As a possible alternative to DAA, the NRoC approach could match a traditional, integrated CMTS with a 5G radio deployed where a DAA node would typically be located. However, sources have noted that NRoC would require a new type of amplifier that could operate below 1.2GHz using DOCSIS and above 1.2GHz using a Time Division Duplex amp for a 5G radio. For delivery in the home, the customer premises equipment (CPE) would need to support both DOCSIS and 5G.

Industry sources say interest in NRoC is high and has gathered more momentum following a recent demo conducted with the CableLabs board of directors. The idea has also been passed along to the CableLabs technical committee, one source said.

Expanding spectrum to 3GHz

Expanding DOCSIS to 3GHz – perhaps as a future spec to be called DOCSIS 4.1 or DOCSIS 5.0 – is another idea that's percolating. The focus is to expand the available spectrum in the HFC plant, paired with a wider FDX band, to enable speeds of up to 25 Gbit/s downstream and roughly 10 Gbit/s in the upstream.

Broadcom is among the companies taking a closer look at the idea, which will need to overcome the power issues that would come with running DOCSIS traffic in that higher spectrum, sources said.

Operating DOCSIS up to 3GHz is not a new idea, as establishing standards around it has been a focus of an SCTE task force in recent years. In 2019, a white paper prepared by engineers at Cisco, Intel and Qorvo presented a blueprint for delivering 25 Gbit/s "PON-like" performance by extending DOCSIS to 3GHz, using 1.8GHz Extended Spectrum DOCSIS as a stepping stone.

Pressure builds on suppliers

Variances in cable network strategies could put more stress on cable tech suppliers that are still trying to figure out which direction the industry may ultimately move. The path chosen will determine how vendors direct their own investments and resources. Suppliers could face a conundrum if cable operators don't all move in unison but instead head in different directions.

"But whatever path is chosen, it has to be a path that is aligned with either Comcast or Charter," one cable operator exec said.

About the Author(s)

Jeff Baumgartner

Senior Editor, Light Reading

Jeff Baumgartner is a Senior Editor for Light Reading and is responsible for the day-to-day news coverage and analysis of the cable and video sectors. Follow him on X and LinkedIn.

Baumgartner also served as Site Editor for Light Reading Cable from 2007-2013. In between his two stints at Light Reading, he led tech coverage for Multichannel News and was a regular contributor to Broadcasting + Cable. Baumgartner was named to the 2018 class of the Cable TV Pioneers.

Subscribe and receive the latest news from the industry.
Join 62,000+ members. Yes it's completely free.

You May Also Like