DOCSIS 4.0 breakthrough could enable ESD cascades without performance loss

Amplifiers have proven to be a sticking point for operators pursuing both full duplex (FDX) and extended spectrum (ESD) DOCSIS 4.0. But industry sources told Fierce an advancement expected to be announced this week will show ESD can deliver on desired performance metrics even when deployed over a cascade of amplifiers.

FDX and ESD face different problems with amplifiers. The former requires the development of next-generation amplifiers with new noise cancellation technology that will allow them to work in the simultaneous transmission environment FDX envisions. FDX devotee Comcast has said it’s hard at work on this front and expects to share more later this year. ESD, meanwhile, is already designed to work with amplifiers. But Dell’Oro Group VP Jeff Heynen said the problem so far has been achieving the 10-gig speeds DOCSIS 4.0 promises over cascades.

“There’s always signal loss and signal attenuation at every amplifier location,” he explained. “When you increase the spectrum, that loss at each of those amplifier stations is even greater. So, there’s an RF signal loss and also a potential bandwidth and throughput loss…the challenge is to be able to deliver the 10-gig speeds without having to touch your existing amplifier cascade.”

The industry sources did not share the technical details of the expected announcement. But Heynen speculated Remote-PHY nodes could give operators more flexibility to adjust OFDM signals and install high pass filters to help prevent signal degradation. Remote-PHY is one of the technology options for a new distributed access architecture operators are looking to adopt as a step on the road toward DOCSIS 4.0.

According to Heynen, the ability to achieve 9- or 10-gig performance with amplifier cascades could be a game changer that allows operators to implement ESD DOCSIS 4.0 faster and cheaper.

“At the end of the day, the cable operators don’t want to touch the existing network if they don’t have to,” he said. “Obviously not having to go out there and touch all the amps that you would have to if this technology didn’t exist, certainly that makes it easier to deploy it.”

“Everybody’s going to ask them the question from now on ‘why don’t you just go to fiber? Why are you still talking about coax cable when fiber is the future?’ This is one of the answers,” he concluded. “If you can get to similar speeds and offer similar speeds to residential customers without having to touch or having minor touches to the existing outside plant, then that’s a huge cost savings” compared to running fiber.