Broadcom's grip on DOCSIS 4.0 chips remains a concern

A mix of initial deployments, multiple product interoperability tests and certification test readiness are all clear indicators that the DOCSIS 4.0 era is plowing forward. But some wrinkles have emerged – namely, easy access to Broadcom's new generation of DOCSIS 4.0 chipsets for modems, amplifiers and nodes.

For now, access to Broadcom's latest DOCSIS technology is limited to a group of tier 1 cable operators that have signed a pricey joint development agreement (JDA) with the chipmaker. Comcast, Liberty Global, Charter Communications, Cox Communications and Rogers Communications are among the JDA group, according to industry sources.

That scenario is concerning for operators outside the JDA, leaving them grasping for answers on how (and if) to move forward on DOCSIS 4.0.

GCI, Alaska's largest cable operator, has been making some moves on the network ahead of a potential transition to DOCSIS 4.0 down the road. Those include the introduction of 1.8GHz amplifiers and "high-split" upgrades that dedicate more spectrum to the upstream.

But access to certain D4.0-powered hardware is a question mark.

"A challenge is understanding what vendor for a mid-tier operator will be able to support that effort outside the JDA," Erik Kuhlmann, senior director of engineering and architecture planning and design at GCI, said last week at Light Reading's Cable Next-Gen Technologies & Strategies event in Denver. "Quite frankly, mid-tier operators are wondering how to get ahead with DOCSIS 4.0 technologies and accessing them outside the JDA."

Broadcom has pledged to open access beyond the JDA eventually but has not specified when that will happen. Light Reading has asked Broadcom whether it has set a timeline.

Update: Broadcom has not issued a comment as of Thursday afternoon. However, an industry source familiar with the matter tells Light Reading that Broadcom is "considering a slightly less onerous version of the JDA for small operators," but it's not clear when that consideration will turn into concrete action.

Kuhlmann said GCI has been reaching out to learn more about potential next steps, but the company hasn't received any concrete answers.

"We are interested in understanding what the next step is for mid-tier operators," he said, noting that GCI intends to get "aggressive" with D4.0 once the path forward becomes clearer.

Other options

But GCI and others outside the Broadcom JDA aren't devoid of options.

MaxLinear's new Puma 8 D4.0 chip is not encumbered by a JDA. However, it is currently limited to the Extended Spectrum DOCSIS (ESD) option for DOCSIS 4.0 specs (Broadcom's new set of unified chips cover both the ESD and Full Duplex options for D4.0).

Operators might also consider a new generation of DOCSIS 3.1 modems that can boost downstream capacity (to around 5 Gbit/s or 6 Gbit/s, and perhaps up to 8 Gbit/s) by supporting additional OFDM (orthogonal frequency division multiplexing) channels and software updates to existing cable modem termination system (CMTS) chassis.

MaxLinear's Puma 8 can run in D3.1 "extended" mode and support up to five 192MHz-wide OFDM channels. A new D3.1 chip from Broadcom, called the BCM3392, will support four OFDM channels and won't be governed by a JDA, according to industry sources.

Given some of the questions swirling around DOCSIS 4.0, Kuhlmann said GCI is keeping tabs on next-gen DOCSIS 3.1 – sometimes referred to as DOCSIS 3.1+, DOCSIS 3.1 extended and DOCSIS 3.1 "stretch."

"I like the term 'stretch'," Kuhlmann said. "DOCSIS 3.1 stretch also stretches our timeframe. It buys us time to provide the faster services that customers are looking for."

Having multiple generations of products designed to versions of the CableLabs DOCSIS specs is not unheard of. Doug Jones, principal architect, broadband access, at CableLabs, noted that there were five generations of DOCSIS 3.0 modems, the last being able to bond 32 downstream QAM channels and 8 upstream channels.

While GCI is not necessarily jumping into a DOCSIS 4.0 platform today, Kuhlmann also sees the potential to run new D4.0 modems on existing D3.1 plant to deliver downstream speeds in the neighborhood of 5 Gbit/s.

'One-touch' plant upgrades

The use of next-gen D3.1 equipment could slow the pace of DOCSIS 4.0 network upgrades, but many cable operators are expected to focus on future-proofing the plant with 1.8GHz technology.

"We're very much interested in deploying 1.8GHz actives as soon as we can get our hands on them," GCI's Kuhlmann said. "The goal for us is to touch that plant once, if at all possible."

Paul Broadhurst, president, founder and group CEO of outside plant specialist Technetix, echoed that. "Anyone who wants to touch their taps or touch their amplifiers, they only want to touch them once, really, in the next 20 years," he said.

Technetix, he added, has developed 1.8GHz plug-ins for many of the top types of amplifiers that have been deployed. As a bonus, the latest wave of amps are also about 25% to 30% less power-hungry than their predecessors, Broadhurst added.

Turning to the node, upgrading a remote PHY device from DOCSIS 3.1 to DOCSIS 4.0 is not trivial, but "it's a relatively light lift," said Ryan Nicometo, SVP and GM of video and broadband solutions at Vecima. Vecima's current lineup of nodes are 1.8GHz-capable, he said.

On the modem side, Vantiva is keeping tabs on next-gen DOCSIS 3.1 and D4.0. The company is gearing up for DOCSIS 4.0 modem certification testing, CTO Charles Cheevers said.

But operators are mulling their options on how to deploy in-home D4.0 devices. While some want an integrated gateway that combines D4.0 and Wi-Fi 7 (Comcast's new XB10 is a prime example), others are exploring architectures that combine a standalone modem with a separate Wi-Fi router, Cheevers said.

Is DOCSIS 4.0 the end of the road?

Panelists were asked if DOCSIS 4.0 is the last chapter in the DOCSIS story. There could be a few more pages left.

Broadhurst noted that Technetix conducted a trial with VodafoneZiggo in the Netherlands last year that pumped out 17 Gbit/s in the downstream on existing plant using advanced 16K QAM technology with 1.8GHz amps and passives. "You might call it DOCSIS 4.0 stretch," he said.

HFC could be extended to 10GHz and support up to 100 Gbit/s, Broadhurst pointed out. But he allowed that it's questionable if demands will call for it and if such a jump is financially viable.

"I think we'll have extended spectrum [for DOCSIS], and there's nobody better than an amplifier supplier to understand what's possible there," said Jones.

"There's plenty of life left in coax cable," Nicometo said. "I'd say at least 20 years."