By Joe McGarvey, Marketing Director |

Much attention in recent months has been focused on MSOs acquiring next-generation cable modems that support additional channel capacity in DOCSIS® 3.1 architectures, enabling cable operators to increase downstream capacity before moving to a full-blown DOCSIS 4.0, 1.8GHz-capable network.

The DOCSIS 3.1 extension, which has been anointed with a flurry of adjectives, including extended, stretch, ultra, plus, and even DOCSIS 3.5, has been profiled in multiple media articles, including here and here. These accounts provide detailed descriptions of the new technology, which essentially amounts to an interim speed boost for DOCSIS 3.1 networks without the need for full-scale infrastructure investments to support DOCSIS 4.0.

In brief, DOCSIS 3.1E, let’s call it, enables MSOs to get more out of their cable access plants by pairing DOCSIS 4.0 modems, or next-gen DOCSIS 3.1 modems, with upgraded Integrated CMTSs or new Virtual CMTSs. The upgrades enable higher bandwidth because the latest modem and CMTS technologies support four or five Orthogonal Frequency Division Multiplexing (OFDM) channels in the downstream. Previous modems were only capable of supporting two OFDM channels.

The in-your-face implication of DOCSIS 3.1E is that MSOs, with minimal investment in DAA and HFC infrastructure (nodes, amps and taps), could deliver — under optimal conditions — about 8Gbps on the downstream channel, as well as roughly 1Gbps on the upstream where a high-split architecture is supported. Those types of service tiers, some industry observers suggest, could provide MSOs with enough runway to compete with FTTH in some service areas in the near term.

Multigigabit Symmetry

DOCSIS 3.1E falls short in the upstream, where DOCSIS 3.1 supports high-split configurations as the maximum spectrum allocation, limiting upstream capacity to 1Gbps. DOCSIS 4.0 Extended Spectrum will empower MSOs to offer multigigabit symmetrical service tiers, such as a 4X4Gbps service offering, which many of those same industry observers argue will be required to give MSOs the ultimate punching power to fend off all-fiber providers well into the future.

How MSOs perceive the strategic significance of the speed gap between DOCSIS 3.1E and DOCSIS 4.0 is likely to impact how they time their network upgrades, a calculation based on how quickly they believe they will need to evolve their HFC plants to meet subscriber demand and fend off all-fiber competitors.

The uptick in downstream capacity delivered by DOCSIS 3.1E means MSOs may need to recalculate current DOCSIS 4.0 adoption plans. As part of that recalculation, MSOs are rightfully wondering if DOCSIS 3.1E will allow them to postpone full-blown adoption of DOCSIS 4.0 or even buy them enough time to complete the ongoing transformation of their networks to all-fiber — without the need to ever upgrade to 1.8GHz.

ATX presented exactly those options to the nearly 150 cable professionals who recently completed the fourth-annual ATX 2050 Project HFC Evolution survey. Preliminary results indicate that a large plurality (42%) of MSOs is still evaluating the technology’s potential impact on DOCSIS 4.0 adoption, suggesting that many MSOs were still working through the math as recently as the beginning of this year. While 24% indicated that it will not impact or alter their current plans, 18% and 16% of survey takers, respectively, said that the technology would likely delay or eliminate a migration to full-blown DOCSIS 4.0.

What impact will the availability of DOCSIS 3.1E have on your DOCSIS 4.0 adoption plans?

Unfortunately, the potential of DOCSIS 3.1E to enable MSOs to delay upgrading their networks to DOCSIS 4.0 does not afford them the luxury of putting off immediate purchasing decisions. That’s because conditioning their networks to support mid- or high-split architectures to deliver extended upstream speeds in a DOCSIS 3.1E architecture will likely require MSOs to upgrade existing HFC amplifiers. The question facing MSOs, then, is whether the next amplifier they purchase should max out at 1.2GHz, or should it be capable of supporting 1.8GHz?

1.2GHz vs 1.8GHz

MSOs leaning toward DOCSIS 3.1E being the final phase in their HFC evolutions might be motivated to update their outside plants with 1.2GHz amps. The major risk associated with going this route is that conditions can change, and should DOCSIS 4.0 be required in the future, MSOs would need to upgrade those same amplifiers with 1.8GHz-capable devices.

The good news is that MSOs also have an option that would eliminate the risk of the potential regrettable spend highlighted above. For a small premium, MSOs can purchase amplifiers, such as ATX’s GigaXtend™ family of GainMaker©-compatible line extenders and system amps, that support 1.8GHz but can also operate in 1.2GHz mode. The benefits of going the 1.8GHz route are numerous, beginning with the peace of mind that comes with knowing your network is DOCSIS 4.0-ready, should you eventually pull the trigger on delivering multigigabit symmetrical services.

In addition, next-gen amplifiers are fortified with electronic controls and with new levels of intelligence that significantly streamline installation and troubleshooting. Not only can 1.8GHz-compatible amps help MSOs reduce technician time on installation and troubleshooting, cut down on installation errors and potentially troubleshoot and tune amplifiers remotely, the smart features built into 1.8GHz amplifiers will lead to smarter and more reliable networks, which means happier subscribers.

The introduction of DOCSIS 3.1E is providing MSOs with options they were not focused on until just a few months ago. It’s also creating its fair share of agita among network engineers and planners that now need to recalculate their network evolution strategies. While the availability of 1.8GHz amplifiers that function in 1.2GHz mode may not deliver immediate Nirvana to network planners, it will eliminate at least one source of heartburn.