Change Ahead – How Network Maintenance Practices Are Evolving With The Rapidly-Changing HFC

The recent pace of change in HFC networks has been dizzying compared to our previous gradual evolutionary path, but fortunately plant maintenance practices including plant leakage detection have evolved to stay ahead of the curve.  The rapid expansion of FTTH offerings combined with the looming threat posed by fixed wireless access have driven many of these architecture and technology changes to stay ahead of competition.

Listed below are a few of these plus some environmental changes:

  • Distributed Access Architectures (DAA) like Remote PHY (R-PHY)
  • DOCSIS 3.1 including new modulations, split changes/frequency extensions
  • Increased off-air frequency sharing

How These Impact Plant Leakage Detection and Resulting Evolutions

DAA/Remote PHY:

Distributed access architectures like Remote PHY generally remove RF from hubs, disallowing combining of RF signal tags into downstreams.  In response leading leakage vendors have worked with the network equipment manufacturers (NEMS) to virtualize signal tagging capabilities enabling the Remote PHY Device (RPD) or DAA node to generate the tag instead.  Using this approach all field equipment and processes are reused, making the transition seamless for technicians in the field.


DOCSIS 3.1 creates several challenges to plant leakage systems and processes

  • Wider OFDM carriers – create up to 192MHz wide blind spots for systems using signal tags alone
  • Frequency split changes – systems with frequency agility only within narrow windows can lose the ability to monitor the bottom portion of the downstream band
  • Frequency extensions – Systems capped at 1GHz are blind to leaks from 1.0 – 1.22 GHz

Adding the ability to detect the OFDM carriers themselves leaking from the plant instead of signal tags is critical to maintaining visibility in a DOCSIS 3.1 plant, be sure to look for this capability when seeking out a leakage solution.  The other major consideration for leakage monitoring in DOCSIS 3.1 plants is absolute frequency agility across the entire spectral range from 130MHz – 1.22GHz.  By enabling monitoring points (tags or OFDM monitoring) to be located anywhere across the spectrum, you can be assured of the most comprehensive coverage.

Increased Off-Air Frequency Sharing

T-Mobile, the third-largest US mobile service provider, is beginning a major public launch for their 600MHz services.  Interesting marketing strategy as other than folks who read technical blogs such as this very few consumers understand what it means to occupy this “new” spectrum band, but cable operators are well-aware of the consequences.

To them this means:

  • Carriers running in this band are going to be more vulnerable to shielding faults due to more/stronger off-air signals in this range, and
  • Egress of their signal into this band will receive more attention if/when it interferes with mobile services

For this reason, a seemingly unrelated announcement by a mobile service provider creates an increased urgency to maintain solid plant integrity and further underscores the need for frequency agility in their go-to integrity tool to monitor this new frequency band.


It has been stated that “The Only Thing That Is Constant Is Change”, and fortunately this holds true for both the cable network itself and the tools that are used to monitor and maintain it.  As cable operators continue to evolve networks to extend HFC dominance over FTTH as the economical gigabit network of choice, you can count on leading test vendors to continue to provide the solutions to efficiently keep them running at their best.


Learn more about VIAVI Cable Signal Leakage

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