Remote PHY 101: Why the Industry Is Working Together to Take Things Apart

In our previous CableLabs 101 post about Distributed Access Architecture (DAA), we discussed the benefits of distributing key network functions throughout the cable access network to optimize its performance. Today, we delve deeper into Remote PHY-one of the earliest DAA solutions that cable operators are deploying to increase their network’s bandwidth and more.

What Is Remote PHY?

Prior to the introduction of the DAA concept, all CCAP functions, including PHY and MAC, were integrated at the Internet provider’s cable modem termination system (CMTS)-typically located at the headend or hub site-which sends and receives data to and from the modem in your home. This data exchange is the basis for how DOCSIS technology on HFC networks works. However, the integrated CCAP approach does not maximize the potential of the cable access network.

Once we figured out how to split the PHY and MAC functions, we were then able distribute PHY closer to the end user, resulting in increased network capacity and greater speeds. You can refresh your memory about the benefits of DAA and Distributed CCAP Architecture (DCA) here.

Remote PHY was the first documented DCA specification that we officially released in 2015, followed by Flexible MAC Architecture (FMA), released in September 2020. These solutions are complementary and have similar benefits, giving cable operators the flexibility to architect their networks the way they see fit to support future high-bandwidth services. The specifications provide guidance to our industry vendors who are manufacturing Remote PHY-compatible equipment. Just like the other DOCSIS and Coherent Optics technologies, Remote PHY and the other DCA approaches are part of the 10G toolset.

How Does Remote PHY Work?

The PHY layer of the CCAP system is placed in something called a Remote PHY Device (RPD). An RPD is a piece of equipment usually produced by a third-party cable vendor that contains all the PHY-related circuitry, as well as the pseudowire logic that connects back to the CCAP Core, which supports full DOCSIS functionality. In other words, all this rerouting on the back end is completely hidden from customers like you. Your network will function the same as before, only much faster because the PHY layer is now located much closer to where you live.

Speaking of location, the beauty of the Remote PHY architecture lies in its flexibility to place RPDs anywhere, including optical nodes closer to the network “edge”-a cable insider’s way of saying “closer to customers’ homes.” A single node can serve just a few blocks or even a single building; therefore, each customer modem connected to that node gets a bigger chunk of the bandwidth pie, so to speak. And, of course, more available bandwidth means better customer experience!

How Does This Technology Affect Me and My Future?

This is why CableLabs and our partners in the cable industry are continuously inventing new ways to mine more bandwidth out of the available RF spectrum. Thanks to specifications like Remote PHY, FMA and others, we have all the pieces in place to deliver 10G symmetrical speeds-and more-to support future innovations. Now it’s just a matter of putting it all together.

Originally published at https://www.cablelabs.com on March 9, 2021.

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Our mission is to create a powerful innovation engine that develops life altering technologies that move communities and industries toward more connected tomorr