The cable industry has relied on Hybrid Fiber-Coaxial (HFC) networks since its launch in the early 1990s. Even as operators eye fiber deployments as the ideal long-term solution, HFC will continue to play a major role in cable networks for many years to come.
But why? We know that FTTH has a lot of advantages – more capacity, superior reliability, lower cost of ownership. So, won’t MSOs just go FTTH everywhere?
Yes and no. Eventually operators will make that choice, but in many parts of the network it might be decades before that happens. HFC, as we will discuss below, has a lot of life, and FTTH presents three critical challenges that operators must overcome:
With these factors in mind, how do operators decide when and where to deploy FTTH and HFC?
Since both the benefits and the costs are high to move to FTTH, most cable operators are using a simple deployment guideline – the brownfield-greenfield rule:
For brownfield environments it is much less costly to simply extend the life of the HFC network. HFC networks have surprised many of us with their ability to adapt and grow with new capacity and application demands. New technology enhancements – such as Distributed Access Architecture (DAA), DOCSIS 4.0, Flexible MAC Architecture (FMA), Extended Spectrum DOCSIS (ESD) and Full Duplex (FDX) – continue to greatly extend HFC’s capacity, reliability, and flexibility. With DAA specifically, operators are pushing fiber and IP deeper into the network, creating a stepping-stone to FTTH. DAA architectures allow for remote OLT devices to service subscribers just like traditional nodes at 80-100km from a main hub, so distance limitations in PON are a relic of the past.
Furthermore, not only does it cost less to extend the existing HFC network, that network by default supports traditional video services, which have historically been a challenge for FTTH deployments. While this is changing, especially in large cities, operators continue to have large investments in their QAM headend equipment and set-top boxes. Fiber deployments in many brownfield environments continue to require RF over Glass (RFoG), an expensive and interim technology that has typically been seen as a either a deterrent or a necessary evil.
Finally, by extending the HFC network there are no changes in the DOCSIS network management or back office.
For greenfield networks – new build – an operator must deploy infrastructure regardless. Whether they deploy HFC or FTTH, the construction costs, which are the largest component of the build cost, are essentially the same, so going FTTH makes sense as you get the above mentioned FTTH advantages at no increased costs when compared to HFC. Figure 4 illustrates the use of FTTH in all-IP greenfield environments vs. R-PHY or R-MACPHY.
In these environments, operators also have more control over both the video services that they offer and they customer premise equipment that they support and deploy. IP services offered on Android TV Operator Tier, Roku devices and zero cost devices – Smart TVs, tablets and phones – eliminate video services as a barrier for FTTH.
Regarding the management and back-office challenge, operators either make a strategic decision to move away from DOCSIS provisioning for their FTTH, or they can use an emulation technology, such as DOCSIS Provisioning of EPON (DPoE). DPoE mimics a DOCSIS network by having the PON Optical Line Terminal (OLT) act like a cable modem termination system (CMTS) and the Optical Network Unit (ONU) act like a cable modem.
Exceptions to the Rule
There are always exceptions to the brownfield-greenfield rule, such as Multiple Dwelling Units (MDUs) and government programs.
MDUs present a unique case. MDU contracts are highly competitive. They are typically for numerous customers over a multi-year period (e.g., 200 units over a 5-year contract MDU is basically the same as 1,000 residential one-year contracts). As a result, owners and residents of premium MDUs often demand FTTH. Furthermore, retrofitting an MDU with FTTH is often a good business choice since fiber can be cost-effectively blown though the building’s existing conduit.
Some countries are putting regulations and requirements in place to drive faster deployment of FTTH. For example, in the United States we have the Rural Digital Opportunity Fund (RDOF), which directly funds fiber deployments to rural areas and is designed to improve quality of life for those communities. In Portugal, they are closing in on national fiber coverage, driven by a national broadband strategy that had a goal to provide at least 30 Mbps for 100% of the population and at least 100 Mbps for 50% of all households by 2020.
The Final Word
As HFC shifts to DAA, DOCSIS 4.0, and the enhancements afforded by ESD and FDX, customers won’t see a difference in the level of services they get over HFC vs. fiber. Thus, the question is which option is most cost-effective from a capital and operational expense. It’s all about the brownfield-greenfield rule.
This blog is the 4th in a series of blogs from Vecima Networks looking at the most asked questions we get regarding DAA and FTTH. The first blog can be found here It discusses “What is the state of DAA standardization and interoperability for R-PHY, R-MACPHY, and Flexible MAC Architecture (FMA)?”
Vecima is always interested in hearing from you. With that in mind, please e-mail to David Slovensky, Vecima Marketing Content Manager at firstname.lastname@example.org if you have questions, comments, or ideas for future blog topics.
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