CableLabs fine tunes DOCSIS 4.0, Remote PHY specs

CableLabs served up its DOCSIS 4.0 specification more than two years ago, but it’s still adding garnishes to the dish as interoperability testing exposes the need for certain engineering tweaks to ensure systems run properly. It’s doing the same with its Remote PHY, Remote MAC-PHY and Flexible MAC Architecture specifications.

Curtis Knittle, VP of wired technologies at CableLabs, told Fierce this refinement is part of the normal process any specification undergoes to smooth out the kinks as it moves from theory to reality. While CableLabs’ engineering team develops specifications with “completeness and integrity and interoperability” in mind, Knittle noted that “until you actually get your hands on the devices, there’s no way you can be guaranteed to not require engineering changes.”

According to Knittle, the process of implementing changes usually takes about 30 days or so. The necessary tweaks are detailed in engineering change requests which can be submitted by anyone, but most often CableLabs members or vendors who are conducting device testing. That request is vetted by CableLabs’ engineering team, which upgrades it to an engineering change order. Once CableLabs officially signs off on the update, it becomes an engineering change notice. Sometimes specifications are rereleased with all the changes incorporated, but either way, the updates are officially part of a given spec once the change notice comes out.

In terms of what exactly is being changed, Knittle said requests can cover a range of things. For instance, maybe a new parameter needs to be added to a MAC message or additional refinement needs to be applied to the physical layer. Perhaps a new packet needs to be developed to deliver information that wasn’t previously sent to the Remote PHY or Remote MAC PHY. Or maybe device vendors interpreted the specification differently and clarification is needed.

Knittle said he expects a steady stream of change requests to come in 2022 and 2023 as CableLabs holds a slew of interoperability testing events covering Remote PHY, flexible MAC architecture and DOCSIS 4.0. This isn’t expected to slow down progress, though.

“I expect the refinement to keep going on even through initial deployments,” he said. “In fact, DOCSIS 3.1 has been out there for a lot of years and operators have been deploying it for a lot of years, and every once in a while we’ll get an engineering change for those specifications.”

While Knittle stressed he could not speak to operator deployment plans, Comcast, Charter Communications, Cox Communications, GCI and Midco have all been vocal about DOCSIS 4.0 being on their respective roadmaps and several stated they are conducting tests of the technology in lab environments.