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?
PHY stands for “physical radio frequency (RF) layer,” which delivers voice, video and data via the DOCSIS® protocol over the hybrid fiber-coax (HFC) network. Media Access Control (MAC) is an example of another CCAP layer that we’ll cover in our next CableLabs 101 post.
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 to 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 Remote PHY specification defines ways to separate the physical RF layer from the MAC layer that remains at the headend and describes the interfaces between them. Let’s take a closer look at how it’s done.
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?
You might think that it makes no difference to you how your Internet provider’s CCAP is designed—and you would be right. What does matter, however, is the noticeable difference in your Internet quality, including how fast your apps work, how quickly you can download your movies or how much lag (or lack thereof) you experience when you play an online game with your friends. Looking forward to the near future, you may be using applications that utilize holographic displays, artificial intelligence, virtual rooms, 360° fully immersive entertainment experiences and other innovative technologies that require multi-gigabit bandwidth to function seamlessly.
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.
DAA 101: A Flexible Approach to Better, Faster Cable Networks
This month, we’d like to share information about Distributed Access Architecture (DAA) and how cable operators are using it to build the 10G networks of the future. In our previous posts about DOCSIS® and Coherent Optics technologies, we touched on some of the components of the cable hybrid fiber-coax (HFC) network, such as the headend and fiber nodes, but of course, there’s much more to it. Today, we’ll take a closer look at the functionality of the cable access network and how it can be distributed between various components to optimize network performance.
What Is Distributed Access Architecture?
DAA isn’t a single technology but rather an umbrella term that describes the network architecture cable operators use to future-proof their access networks. This network evolution involves moving various key network functions that are traditionally located at the cable operator’s hub site (or headend) closer to customers’ homes—while also leveraging signal-quality improvements inherent with digital optics and the ubiquity of Ethernet. In addition, closer is better because it reduces the amount of hardware at the headend and creates efficiencies in network speed, reliability, latency and security.
In a nutshell, CableLabs’ DAA technology solutions give cable operators the ability to cost-efficiently redesign their access networks in stages, when and how they see fit. Because all providers’ business objectives are different, CableLabs has designed several DAA approaches they can leverage. Ultimately, it’s all about building a robust 10G network that not only supports the needs of today’s gig consumers but also anticipates tomorrow’s high-rate applications such as holodecks, artificial intelligence (AI), virtual reality (VR) and more.
Let’s take a look at one particular embodiment of DAA, known as Distributed CCAP Architecture (DCA).
How Does Distributed CCAP Architecture Work?
In a traditional HFC network architecture, the operator’s hub—or headend—is connected via fiber to the fiber node in your geographical region. In the fiber node, the optical signal is converted to a radio frequency (RF) signal that travels via a coaxial cable to the cable modem in your home. The key functions responsible for the transmission of data and device access are placed at either end of the operator’s access network—the hub and the modem—like bookends.
In 2015, CableLabs figured out how to split the key DOCSIS network functions into two components: a Media Access Control (MAC) layer that’s responsible for how devices in a network gain access to the network, and a Physical (PHY) layer, a physical component that’s responsible for the transmission and reception of data. Decoupled, these components can now be partially or fully moved from the headend into a fiber node closer to subscribers’ homes, resulting in increased network capacity, greater speeds, lower latency and so on. That’s the basis for DCA.
How Can Distributed CCAP Architecture Help Build Better Networks?
Distributing key DOCSIS network functions out of the headend and closer to subscribers’ homes comes with many benefits. Primarily, it allows operators to:
- Maximize Their Network’s Potential
DCA allows cable operators to take full advantage of the gigabit capabilities of Coherent Optics and DOCSIS 3.1 technology, including Full Duplex DOCSIS and Low Latency DOCSIS. This means their networks will have more than enough bandwidth to support the latest-generation products for years to come.
- Achieve a Better-Quality RF Signal
With distributed architecture, the RF signal that usually originates in the regional hub can now originate in the optical node, closer to the subscriber’s home, thus reducing distortion and creating a more seamless user experience.
- Increase Network Reliability
Because the main functions of the network no longer need to be housed at the headend, the access network can be redesigned so that fewer homes are connected to any single optical node (where the fiber and coax portions of the network meet). This means that if there’s an outage, it will affect fewer customers, ultimately increasing the reliability of the overall network.
- Expand RF Spectrum in the Future
Because DCA solutions are easily customizable and budget-friendly, they provide new opportunities for cable operators to expand their RF spectrum (basically maximizing the capacity of the coax portion of the HFC network) to support future services.
How Does This Technology Affect Me and My Future?
Widespread adoption of DCA, and importantly the superset of capabilities provided by DAA, is essential to creating the 10G future that we’re all looking forward to. And although it might seem that DAA only provides cost-effective solutions for cable companies, ultimately the real beneficiary is you, the customer. By reimagining and reinventing cable access infrastructure, we’re finding greater efficiencies that translate into more powerful networks. These networks will enable a wave of new, innovative services that will transform the way we live, learn, work and play.
Just like DOCSIS technology, Coherent Optics and other technologies that we’ll be covering in our 101 series, DAA is another piece of the puzzle responsible for propelling cable’s HFC networks into the new decade and beyond. Stay tuned for another installment—coming soon!
Remote PHY is a Reality
Just over two years ago, CableLabs announced the release of a new series of specifications known as “Remote PHY” in the blog “CableLabs® New Remote PHY Specifications expand DOCSIS® Network Deployment Options” authored by CableLabs principal architect Karthik Sundaresan. The blog describes what Remote PHY (R-PHY) is, how it forms a key piece of the various Distributed Access Architecture options we have established at CableLabs and upcoming plans for the further development of the technology.
Distributed Access Architectures and Remote PHY technology, in particular, provide several key benefits to the Hybrid Fiber Coax (HFC) networks that deliver cable TV and broadband to consumers and businesses:
- Takes full advantage of the capabilities of DOCSIS 3.1 technology, allowing more data capacity to be packed into the same amount of spectrum
- Supports the deployment of Full Duplex DOCSIS, which will enable multi-gigabit upstream services on existing cable plants
- Leverages lower cost/higher capacity optical Ethernet transport mechanisms, allowing cable operators to cost-effectively provide faster services to customers
Since this announcement, hundreds of engineers on dozens of teams from CableLabs, equipment manufacturers and cable operators worked vigorously to move the technology forward. We’re excited to announce that as a result of this hard work, interoperable Remote PHY devices (RPDs) now exist and will be available on the market soon.
What is Remote PHY Technology?: A Technical Recap
The R-PHY technology pushes the physical RF layer (PHY) to the edge of the access network. This design requires the CCAP to be “split” between the MAC layer and the PHY layer. In an R-PHY system, the integrated CCAP is separated into two distinct components. The first component is the CCAP Core and the second component is the RPD. The CCAP Core can contain both a CMTS Core for DOCSIS technology and an EQAM Core for Video.
The RPD contains PHY-related circuitry, such as downstream QAM modulators, upstream QAM demodulators, together with pseudowire logic to connect to the CCAP Core. The RPD platform is a physical layer converter whose functions are:
- To convert downstream DOCSIS, MPEG video and out-of-band signals received from a CCAP Core over a digital medium, such as Ethernet or PON to analog for transmission over RF.
- To convert upstream DOCSIS and out-of-band signals received from an analog medium, such as RF to digital for transmission over Ethernet or PON to a CCAP Core.
Testing Products at CableLabs’ R-PHY Interoperability Events
While CableLabs is known for developing specifications, we also work extensively to help manufacturers develop products that conform to our specifications and interoperate with one another. One important means of doing so is through interoperability events.
The start of interoperability testing is a crucial milestone in the lifecycle of a project at CableLabs. It represents the point at which products become real and can start to work with one another. CableLabs serves as the neutral ground that allows manufacturers, who might otherwise be competitors, to come together and – for the very first time – validate whether or not their implementations work with each other and, if not, figure out why. This is a major step for manufacturers to validate their products are commercially viable.
CableLabs hosted a series of one to two-week long interoperability events, starting in December of 2016. These events comprised of 15 equipment manufacturers from around the world. The initial events included prototype RPDs and CCAP Cores which delivered product interoperability from the beginning. Over the course of time, the products matured until they became ready for use in field trials - a massive progression of development.
As participants continued through their development of RPD and CCAP Core products, features and requirements were added to the events to advance product readiness. A number of key features to enable commercial deployment were tested and verified: RPD initialization, IPv6 support, timing, DOCSIS 3.1 network operation and the creation of and communications through upstream/downstream L2TPv3 tunnels.
Announcing the Remote PHY Device Qualification Program
As an additional step to ensure devices are ready for deployment, where appropriate, CableLabs develops Qualification Programs to formally test and verify that devices comply with the specifications. This indicates that they will successfully interoperate with one another when deployed in the field. Based on the success experienced in the interoperability events to date, CableLabs is excited to announce that we have now launched a Qualification Program for the testing of RPDs.
Similar to our highly successful DOCSIS certification programs, manufacturers can now submit RPDs, whether they’re in R-PHY Nodes or R-PHY Shelves, for formal qualification testing at CableLabs. Once submitted, these devices are extensively tested by our partner Kyrio to ensure that they comply with our specifications and that they will successfully interoperate with other compliant devices.
Remote PHY is Real
CableLabs’ Interoperability Events help to get devices to that point and the start of our Qualification Program ensures that devices are able to demonstrate their compliance and readiness.All of this serves to demonstrate that Remote PHY is real: products are real, they are here and they’ll see deployment in the field soon. This means that cable operators – and ultimately their customers – benefit from Remote PHY deployments.
Remote PHY Industry Events & News
R-PHY is playing a major roll in the cable industry and the timing couldn’t be better! This year’s SCTE Cable-Tec Expo® in Denver, CO is holding an R-PHY seminar on Tuesday, October 17th. This event will provide an in-depth look at all aspects of R-PHY including the technology, the implementation of R-PHY and the benefits for operators. Jon Schnoor is speaking at the seminar, providing a view of the current state of the project and how CableLabs and Kyrio are playing an essential role in the next generation of cable networks.
Interested in reading more about Remote PHY in the future? Subscribe to our blog and let us know your thoughts in the comment section below.