- Cable operators are ‘milking’ the DOCSIS 3.1 standard by pursuing mid-split and high-split upgrades
- Upping spectrum bandwidth enables higher upstream speeds without ‘reform[ing] their network with new amplifiers,’ said ATX’s Jay Lee
- Charter will use ATX’s 1.8 GHz amps and nodes for high-split upgrades
As appealing as getting to 10G ASAP sounds, taking apart the old network and revamping it can be time-consuming and costly for cable operators. So instead, they’re “milking” DOCSIS 3.1 before making the switch to 4.0, according to Jay Lee, chief technology and strategy officer at ATX Networks.
It's been more than a decade since CableLabs released the DOCSIS 3.1 specifications in 2013. But operators still want to make the most of what the standard has to offer. That's in part because moving to DOCSIS 4.0 is harder than it might seem at first glance.
The idea behind DOCSIS 4.0 is to upgrade the network in a “drop-in” manner, Lee said in an interview with Fierce at SCTE TechExpo '24, meaning you’d go up to an amplifier, remove the module and plug in a new one. Sounds simple, right?
However, every amplifier is situated in a “predetermined, negotiated with a municipality location” in the network. Operators don’t want to waste time and money to rebuild their entire network and “re-space or re-locate where those amplifier devices were,” he explained.
That’s where mid-split and high-split upgrades come into play. These alter the amount of spectrum allocated for upstream traffic flow. Cable companies have traditionally used a low-split (or sub-split) band for upstream speeds, which has a small spectrum range of 5 MHz to 42 MHz.
“Obviously that’s been a bit of an Achilles heel for the cable industry,” Lee noted, referencing fiber's push to offer symmetrical upstream and downstream speeds.
In a mid-split, 5 MHz to 85 MHz is dedicated for upstream traffic, while high-split goes even further to extend the upstream range to 204 MHz. Upping the spectrum bandwidth is a key adjustment to make as consumers continue to increase bandwidth consumption.
By doing so, operators can provide higher upstream speeds without having to go back and “reform their network with new amplifiers,” said Lee. Instead, they can just reconfigure those amps when they eventually upgrade to 4.0.
Charter, which is pursuing high-split upgrades, recently announced it will use ATX’s 1.8 GHz amplifiers and nodes for its network deployment, paving the way for extended spectrum (ESD) DOCSIS 4.0.
Similarly, operators GCI and Rogers said during the show they’re undertaking high-split and mid-split upgrades, respectively, to improve reliability across all parts of the network.
There’s also a hybrid modem setup that can provide cable companies higher downstream and upstream speeds, as CableLabs has shown, by connecting a DOCSIS 4.0 modem with a 3.1 cable modem termination system (CMTS) in a high-split configuration.
This “extended” DOCSIS 3.1, as it’s often called, is pretty important for small, regional cable operators who don’t have access to the DOCSIS 4.0 tech the larger MSOs possess, Lee pointed out.
The big guys, meanwhile, are starting to think about how to go beyond 10G. Comcast and Charter are partnering with chipmaker Broadcom to develop “unified” DOCSIS 4.0 chipsets. These chips would be compatible with both full-duplex (FDX) and extended spectrum (ESD) DOCSIS 4.0 and eventually allow operators to go up to 25 Gbps downstream speeds.
Picking up where Cisco left off
ATX’s 1.8 GHz GigaXtend node, which the vendor unveiled last year, is based on Cisco’s GS7000 node technology. Back in 2020, Cisco exited the cable amplifier space and sold off that business to ATX.
“They didn’t just want to abandon their customers they had for a number of years, [so] we were able to secure a technology transition agreement,” Lee said.
ATX’s motivation around the deal was “we knew customers had a lot of this installed base that they would want to evolve over time [and be able] to do that sort of modular upgrade, as opposed to having to cut an amplifier and put a new one in,” he added.
But do operators have enough workers for the task? “Just the sheer mass of folks they need to support these upgrades” is a challenge, Lee acknowledged.
“It’s a bit of a double whammy, because the whole reason MSOs are upgrading the networks is to compete. Which means the competitors on the other side, they’re building and upgrading networks as well,” he said. “Everybody is kind of in the same labor pool.”