Heynen's SCTE takeaways: DOCSIS 4.0 decisions loom, DAA tide turns

In years past cable operators, deservedly proud of constantly evolving and improving DOCSIS networks, have generally dismissed fiber as an overbuild technology because of its high costs to pass and connect homes. But with competitors new and old seizing on a funding environment designed specifically to lower the economics of deploying fiber and passive optical networks (PON), cable operators are now accepting fiber as the logical evolution of their networks.

Though cable operators’ DOCSIS journey will inevitably lead to fiber, this year’s SCTE Cable-Tec Expo demonstrated that there is still plenty of gas left in the DOCSIS tank, especially when it comes to DOCSIS 3.1. Many operators are currently deploying mid-split and high-split architectures designed to allow them to deliver anywhere from 400 Mbps to 1 Gbps of upstream bandwidth. Both architectural moves are cost-effective ways to upgrade and remain competitive with fiber overbuilders in the short-term, while also making evolutionary steps towards DOCSIS 4.0 and/or fiber-to-the-home (FTTH).

Beyond DOCSIS 3.1, however, there is far less consensus on the path forward. Even the question of just how long operators can use DOCSIS 3.1 to remain competitive in this new environment remains up for debate. Some operators and vendors have argued that DOCSIS 3.1 with high splits, combined with the rollout of remote PHY nodes and re-use of QAM spectrum previously used for digital video services will provide more than enough capacity to remain competitive through 2025 or longer. Others, likely facing more immediate threats, argued that their current DOCSIS 3.1 high-split initiatives would take them through the end of 2024, at which point their transition to DOCSIS 4.0 or FTTH would likely have to begin in earnest.

Speaking of DOCSIS 4.0, quite possibly the biggest news of the show was Comcast’s demonstration of full duplex DOCSIS 4.0 (FDX) using a node+6 architecture, which is generally the most common amplifier cascade in use among North American cable operators. Earlier this year, Comcast demonstrated a full duplex using a node+2 architecture and teased node+6 as a viable target. With node+6 now a realistic option, there will undoubtedly be operators which were completely on board with 1.8 GHz extended spectrum DOCSIS 4.0 (ESD) that will kick the tires of Comcast’s solution to see if it is both technically and economically feasible for their networks.

As a technology, ESD owes its existence to Comcast’s early desire to ultimately move its entire footprint to node+0, even though early FDX designs and prototypes showed that FDX could deliver symmetric, multi-gigabit services in node+5 environments. Comcast’s fiber-deep focus resulted in vendors and component suppliers chasing revenue that was never going to materialize. But, what’s old is new again and, within the span of fewer than six months, Comcast has demonstrated FDX’s throughput with cascades of up to 6 amplifiers. Now, an additional crop of vendors which have committed R&D and manufacturing resources for 1.8 GHz amplifiers have to be wondering what their ROI might be if more operators opt for 1.2 GHz FDX deployments.

As with all new technologies, there are trade-offs. FDX will still require brand new amplifiers, nodes and modems with DSP silicon that can handle echo cancellation. The integration of echo cancellation into those units will result in additional costs per unit, as well as added complexity. On the positive side, most current taps can remain in place. The same can not be said for 1.8 GHz ESD upgrades, which will also require amplifier swaps in addition to taps and other passive elements. With labor shortages and costs still a critical consideration of any new buildout, not needing to touch any taps in neighborhoods is very attractive. Also, replacing taps does require service to be shut off for a period of time—always an important consideration for operators, especially when their competition would likely exploit any service disruptions.

ESD, on the other hand, is what operators know. They have decades of experience adding spectrum and capacity through amplifier, tap and passive swaps. There is no new spacing of the amplifiers to be done. Also, operators can go ahead and upgrade the amplifiers first and then tackle tap upgrades, as most taps in the field today support up to 1.2GHz. That way, operators can derive some spectrum upgrades without having to do the heavy lifting of tap upgrades right away. Choices beget choices.

Should operators want to dispense with the question around node, amplifier and tap upgrades and move to fiber, there are now enough remote OLT (R-OLT) platforms available to allow them to begin delivering FTTH in both greenfield and overbuild scenarios. Adtran, Calix, Ciena, CommScope, Harmonic, Nokia, Technetix and Vecima were all demonstrating R-OLT platforms at the show. Each platform offered some degree of functional differentiation, with Ciena focused on combining FTTH service delivery and aggregation from a single node location and Harmonic providing direct integration with existing DOCSIS management standards. Others, such as Vecima, highlighted interoperability, a key component easing a transition to full fiber.

We are indeed seeing the most significant growth in R-OLT ports, particularly in the North American market, as these platforms allow cable operators to introduce FTTH to a service group of 32-64 homes from existing node locations. In some cases, the R-OLT modules can be housed alongside Remote PHY devices, so that both can take advantage of Ethernet transport back to the headend or hub site, with subscriber endpoints all managed through the same virtual broadband network gateway (vBNG) or virtual cable modem termination system (vCMTS) platform.

Remote PHY is leading the DAA push

When it comes to distributed access architectures, it appears that Remote MACPHY is now falling out of favor throughout the industry. With the competitive environment changing so dramatically and with operators feeling pressured to upgrade their networks today, it appears that a growing list of operators is moving forward with a combination of Remote PHY and vCMTS. Concerns around Remote PHY latency seem to have diminished even in the potential case of processing mobile traffic.

This isn’t to say that Remote MACPHY is going away entirely. There will still be operators who prefer the simplicity of the architecture. But the heightened sense of urgency that was palpable on the show floor is clearly being translated into a need to adopt Remote PHY sooner rather than later.

The implications of this shift on Cablelabs’ proposed Flexible MAC Architecture (FMA) have yet to be seen. However, its heavy focus on Remote MACPHY is likely to be softened to incorporate more Remote PHY elements - it is flexible, right? Meanwhile, vCMTS platforms can still be disaggregated into functional piece parts including the MAC manager, PacketCable Aggregator, etc. In fact, this might be the opportunity to more clearly define the role of R-OLTs in the FMA specification as they are likely to become the “new” Remote MACPHY for cable operators who want to move forward with both DOCSIS and FTTH networks.

Jeff Heynen joined Dell’Oro Group in 2018, and is responsible for the Broadband Access and Home Networking market, Fixed Wireless Infrastructure and CPE market research programs. He has expanded the Broadband Access and Home Networking areas to include fixed wireless CPE, virtual CCAP, Remote PHY, Remote MACPHY and DOCSIS 4.0 infrastructure. Heynen is a frequent judge and expert speaker at industry conferences and his research and analysis have been widely cited in leading trade and business publications.

Industry Voices are opinion columns written by outside contributors—often industry experts or analysts—who are invited to the conversation by FierceTelecom staff. They do not represent the opinions of FierceTelecom.