- There’s no one-size-fits-all approach for DOCSIS 4.0 deployments
- Some operators are leaning towards both ESD and FDX DOCSIS 4.0 depending on the configuration of their footprints
- Comcast, first out the gate with commercial 4.0 rollouts, is helping other cable cos with network upgrade paths
DOCSIS 4.0 is often regarded as the holy grail for cable operators in their quest for faster internet speeds. But with all the specifications and acronyms out there (3.1, 4,0, ESD, FDX, etc.), it can be pretty confusing to make sense of how the industry is actually progressing with network upgrades.
There’s no one-size-fits-all approach for the cable upgrade path, according to CableLabs CEO Phil McKinney. Operators have to strike a balance between what their network looks like today, what kinds of customers they’re serving and what services they want to deliver.
“The great thing about DOCSIS [is] there’s lots of options on lots of knobs,” he said in an interview with Fierce at SCTE TechExpo. “Every member can pick and choose what their migration path is.”
Essentially, DOCSIS 4.0 is about how you can “open up as much spectrum as possible to send as many bits as fast as possible” to reach 10 Gbps speeds. Operators are also thinking about how a 3.1 Cable Modem Termination System (CMTS) can take advantage of all the bandwidth that’s natively built into the 4.0 modem.
Basically, you’ve got this “racecar” in the form of a modem, McKinney said, and you’re wondering if you can “plug it into” an existing CMTS and whether it’s compatible.
At a CableLabs interoperability event last year, operators tested a hybrid DOCSIS 3.1 CMTS+4.0 modem setup that reached around 8 Gbps downstream. This technology is often referred to as “3.1 Extended,” though McKinney noted that’s not an official CableLabs term.
For each CableLabs specification, a device is “backward compatible” to work with earlier versions, he explained, which means a CMTS can work with 3.1, 3.0, or even DOCSIS 2.0 modem.
“By default, the specification says that a 4.0 device has to work with a 3.1. So it’s not any new feature, not something extra that has to be done,” McKinney said. “It is unique in the fact that it does allow you to take advantage of more channels that [the silicon of 4.0] can support.”
A hybrid 3.1/4.0 setup can be a less expensive option for cable operators to “achieve billboard speeds that are typically better than what fiber ISPs offer,” Dell’Oro Group VP Jeff Heynen told Fierce earlier this year.
ESD vs. FDX?
Operators typically have two DOCSIS 4.0 flavors to choose from: extended spectrum (ESD) or full-duplex (FDX).
Comcast for instance is pursuing FDX, which essentially allows upstream and downstream traffic to flow over the same 1.2 GHz chunk of spectrum. Others, like Charter and Cox, are taking the ESD route, which lets them add up to 1.8 GHz of spectrum for faster speeds.
But are operators particularly gravitating towards one or the other? McKinney doesn’t think so. In some cases, operators could use both ESD and FDX because “there’s advantages to each one.”
FDX, for instance, is more appealing for operators that have a lot of “high density MDUs [multi-dwelling units]” in their footprints. For ISPs that are more rural and “have more cascades,” or a larger number of active devices, ESD is “more efficient.”
It’s not more complicated to run both ESD and FDX on the same CMTS, McKinney said. “You just choose which modem you want to run for that house.”
“The modems look the same. They operate the same, same provisioning, same data for proactive network maintenance,” he said. “It just really gets down to, what is your current topology of your network and therefore, how do you take advantage of what you have?”
The road to 10G and beyond
So far, DOCSIS 4.0 adoption is “pretty much on plan” with operator field trials, McKinney said. Though Comcast was first out of the gate with commercial rollouts, all CableLabs members “have some 4.0 deployments in process today.”
It’s not like Comcast is trying to “leapfrog” ahead of other operators with DOCSIS 4.0. There’s usually one member that “takes the lead in the next generation,” with McKinney pointing out Mediacom was actually the first to deploy 3.1 several years ago.
Comcast is “extremely transparent” with other operators on the work it’s doing for 4.0 deployments, McKinney said. For example, it could inform other ISPs “if you’ve got a home that’s got this kind of splitter, there could be a problem.” Or that it ran into an issue stemming from “some network we acquired 10 years ago and nobody ever bothered to look behind the wall.”
Comcast also announced last week it’s begun live deployments of CommScope’s FDX amplifiers.
“When you do that truck roll and you’re actually dropping a modem into a customer’s house, that’s where the rubber meets the road,” McKinney said.
Overall, DOCSIS 4.0 is working “pretty effectively” in existing plants, because operators don’t need to do “massive re-spacings of your taps or amps.” Some operators and vendors are taking it a step further and trialing ways to extend usable downstream spectrum up to 3 GHz, said McKinney, “not just the 1.8.” That could give ISPs the option to say, install 4.0 modems on a 3.1 CMTS and then wait and do “a plant upgrade for 3 GHz” to get higher speeds.
Extending spectrum to 3 GHz could open the door to speeds beyond 10 Gbps. Broadcom, Charter and Comcast recently announced they’re collaborating on the development of “unified” DOCSIS chipsets that would be compatible with both ESD and FDX DOCSIs 4.0 deployments – paving a way to deliver downstream speeds of 25 Gbps.
