Broadcom JDAs for DOCSIS 4.0 chips are 'problematic,' but doesn't halt HFC upgrades

A joint development agreement (JDA) that limits access to Broadcom's new DOCSIS 4.0 silicon is an impediment for some cable operators that are not yet participating in it. But such restrictions apparently do not prevent operators from pushing ahead with hybrid fiber/coax (HFC) network upgrades.

That JDA centers on a family of "unified" D4.0 chips from Broadcom (with contributions from Comcast) that covers the specifications' two options – Full Duplex (FDX) and Extended Spectrum DOCSIS (ESD). Operators that have signed to the latest JDA (or are in the process of doing so), include Comcast, Charter Communications, Rogers Communications, Liberty Global and Cox Communications, industry sources said.

The JDA, which also includes certain volume commitments, isn't cheap. As Light Reading reported in January, participation costs up to $20 million. JDA members will get first crack at the technology. Broadcom has pledged to open up access eventually, but has not announced an anticipated timeline for that. That's creating a degree of uncertainty for operators that are on the outside looking in.

"The JDA has been a little bit problematic for our planning purposes, but it really doesn't change ultimately our ability to upgrade our network and leverage DOCSIS 3.1 to the greatest degree possible," Erik Kuhlmann, senior director of engineering and architecture at GCI, said last week during a "LiveLearning" webinar focused on DOCSIS 4.0 developments hosted by Light Reading in conjunction with SCTE. "Right now, our upgrades continue…to stay ahead of the utilization that our customers are demanding."

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

GCI, Alaska's largest cable operator, is currently deploying 1.2GHz active components and 2GHz passive elements into its HFC network, and will pivot to 1.8GHz actives as soon as those products become widely available. That is also enabling GCI to move ahead with "high-split" upgrades that dedicate more spectrum to the upstream and, generally, squeeze more performance out of its DOCSIS 3.1 network. GCI, like several other mid-sized cable operators, is also taking a closer look at new, upgraded D3.1 technologies that will allow it to add more downstream speed and capacity by opening up and accessing additional orthogonal frequency-division multiplexing (OFDM) channels.

Beyond that, such work also sets the state and the foundation to support DOCSIS 4.0, "when it's ready for mass production," Kuhlmann said.

And while the JDA inserts some uncertainty into the picture for some operators, there are other options to consider. Kuhlmann noted that GCI and other operators do have access to the Puma 8, a new D4.0 modem chipset from MaxLinear that supports the ESD option of the specs and is not encumbered by a JDA. The Puma 8, which packs 5 OFDM downstream channels, can also run in D3.1 mode.

Related:Broadcom's grip on DOCSIS 4.0 chips remains a concern

Brady Volpe, chief product officer OpenVault, said the JDA approach has some advantages, in that the group can advance the technology tailored to their specific needs. The downside, he said, is that it could "fragment" the industry and exclude cable operators and suppliers that can't afford the "large entrance fee" to get into the JDA.

That could lead some operators to abandon DOCSIS 4.0 in favor of enhanced D3.1 technologies or eventually migrate to fiber-to-the-premises (FTTP) technologies, he said.

Kuhlmann noted that some of the haziness about access to DOCSIS 4.0 technologies is causing the operator to question how much longer it will invest in HFC plant, which is 30 years old in some instances.

"I think there's an inflection point coming," he said. "I don't know where that is just yet for GCI. It's likely several years down the road because we have a pretty good plant and we're staying ahead of those upgrades, but time will tell."

GCI is exploring 1.8GHz upgrades, but "I can tell you right now that operating at 1.2GHz is a challenge already," Kuhlmann explained. "There's a lot of work to be done today. That work is taking longer than we expected." As a result, "our timelines have shifted," he added.

Panelists agreed that DOCSIS 3.1, considered a bridge to D4.0, still has plenty of runway left – perhaps five or ten more years.

SLAs and DOCSIS 4.0 might make a good match

But there are other good reasons for operators to keep an eye on DOCSIS 4.0, as its distributed access architecture (DAA) puts operators on the path to software-defined, virtualized networks and more secure, reliable networks, Rob Wilmoth, chief architect at Red Hat, said.

Others noted that DOCSIS 4.0 also provides a way for cable operators to improve quality of service capabilities and put them in position to offer service level agreements (SLAs) for businesses that can guarantee elements such as speed and latency rather than having to focus on "best effort" services.

"If we're going to remain relevant and compete with fiber we need to be talking about SLAs," Kuhlmann said. "We need to look at it beyond best effort and we have the toolset in front of us to do that with DOCSIS 4.0."

Looking beyond D4.0?

Meanwhile, the cable industry is also starting to explore what might come after (or maybe complement) DOCSIS 4.0. Charter Communications, Rogers Communications and CableLabs are looking at a way to run 5G signals above 1.2GHz and up to 4GHz or 5GHz. Others continue to weigh the potential to operate DOCSIS in spectrum up to 3GHz.

"Time will tell, but I'm very optimistic that we can really wring a lot of capacity out of the existing copper plant that we have today," Kuhlmann said.

There are also ways for cable operators to play with the way the spectrum is being split and support current usage trends that continue to show that most broadband usage remains downstream-heavy. Rather than going with symmetrical speeds, operators could dedicate enough spectrum to beef up the downstream and deliver truly what is necessary in the upstream.

Some cable operators are also taking a look at downstream speeds of 13 Gbit/s to 15 Gbit/s by limiting the upstream to about 1.5 Gbit/s, noted Thuy Nguyen, head of cable segment, network platforms group, Intel Corp.

It's also possible to run PON off a node to support service groups where it makes sense to do so.

Effectively, such projects will continue to provide many paths for the cable industry to take, Nguyen said. "There's no killer app [yet] that will consume that kind of bandwidth, but the options are fantastic," he said.

But Volpe also warned that operating DOCSIS at 3GHz could cause maintenance costs to rise as operators grapple with things such as loose connectors and corrosion. As speeds start to get into the neighborhood of 25 Gbit/s, he said it might make more sense for an operator to drop in fiber because the cost to upgrade and maintain HFC plant to compete at that level could become prohibitively expensive.  

"I think these are decisions the cable operator makes rather than the technology makes, just from a cost and challenge standpoint," he said.