While 10G will be a hot top at this week's virtual SCTE•ISBE Cable-Tec Expo 2020 conference, but there's a lot of blocking and tackling currently under way for expanding the upstream capabilities across cable operator's HFC networks.
As a whole, the cable industry's upstream held up well during the Covid-19 pandemic, but with the increased use of video conferencing and other tools associated with work-from-home and online learning, cable operators need to accelerate their efforts on expanding the upstream according to CommScope CTO Tom Cloonan.
"In the upstream, we've seen that it's grown by about 25% over what it was in February," Cloonan said. "So that's a big jump. That's just a massive, sudden, big jump that nobody had anticipated."
Splitsville for cable
Overall, most cable operators were able to adjust their configurations, node splits and node segmentations during the March-to-April timeframe, but Cloonan said Covid-19 accelerated their plans to do mid-splits at 85MHz and high-splits to 204MHz for their upstreams. Currently, most cable operators have a return band of 5 MHz to 42 MHz on the upstream.
"In all honesty, the upstream was really the area that was most challenged by the Covid hit," Cloonan said. "The upstream was where a lot of the operators really saw that they needed to work harder on. Going to 85MHz, or 204MHz, would definitely reduce those issues, and allow the operators to move very deep into the future without issue for a long time because that gives them a lot of extra bandwidth capacity for the upstream.
"So we expect, and are already seeing, a lot of operators planning to do that and working to get their components in the field up to snuff to do that kind of thing."
Moving to the mid and high-splits will awaken several features on DOCIS 3.1 that have been dormant over the years until they were needed. For starters, cable operators will have to make changes in their amplifiers and the nodes.
"When you look into the more distant future, a lot of operators realize that eventually they're probably going to need more than 204 megahertz upstream capacity," Cloonan said. "And that's where the DOCSIS 4.0 spec comes into play. "
"It offers the operators several things. They can take their upstream capacities and go beyond 204 megahertz. They can go to 300 megahertz, 396, 492, or 684 megahertz. So it really allows them to push the splits up to much higher levels, giving them much higher upstream bound capacities for the future of their network operations."
Moving to the "ultra high-split" would entail making changes on the downstream, which could include full duplex DOCSIS or pushing the downstream from 1.2GHz to 1.8GHz as part of DOCSIS 4.0's expanded spectrum DOCSIS.
Moving forward on 4.0
Cloonan said silicon vendors and system vendors such as CommScope are working on the elements that are needed for 4.0, which could be available in the 2023 to 2025 time frame.
"We'll likely see different products show up at different time phasings going forward," he said. "You'll likely see passives, like taps, showing up first. And then you'll see probably amplifiers following that and probably nodes following that. So you'll see different releases of products from the vendor community for operators, and different operators will turn it on at different times.
"Maybe they choose to start deploying it in 2024, but they may not actually enable the new capabilities until 2026 or 2030 or 2033. So there's probably going to be a period of time where the DOCIS 4.0 features will live in the network as latent features just like 204 Megahertz has been a latent feature for DOCSIS 3.1 for quite a few year. I think we will see 684 megahertz being a latent feature inside of DOCSIS 4.0 for quite a long time as well."
In order to take advantage of DOCSIS 4.0, Cloonan said cable operators would need to make several changes to their outside plants.
"Those changes may include tap changes for extended spectrum DOCSIS," he said. "Or with both extended spectrum DOCSIS and full duplex DOCIS, we will have to make changes to amplifiers and nodes. So those changes take some time because they have a limited number of bucket trucks that go out every night to make those changes. So we're going to have to allow several years for all these changes to take place."
OFDM a near-term boost for upstream
While DOCSIS 4.0 is on cable operators' roadmaps, including as means to get to symmetrical 10-Gig speeds, Cloonan said cable operators could improve their upstreams now with orthogonal frequency division multiplexing (OFDM) subcarriers in DOCSIS 3.1. In a nutshell, Cloonan said OFDM and OFDM-A carriers allow cable operators to get more bits per second per hertz.
"Right now, a lot of operators are starting to consider turning on OFDM, or are turning on OFDMA, which is a piece part of DOCSIS 3.1 that has also lived latent for about five years," he said. "Now they're starting to turn it on to increase the throughputs in the upstream as we enter this post-Covid era.
"I think we'll see upstream capacity increases first and then likely downstream capacities will follow suit. So it's going to be a lot of stages of different features getting rolled out over the next five to 10 years from both DOCSIS 3.1 specs and DOCSIS 4.0 specs."
Low-latency DOCSIS a game-changer for gamers
Cloonan said DOCSIS 3.1 also includes low-latency DOCSIS, which he said would be particularly appealing to gamers. Low-latency DOCSIS enables operators to reduce the jitter and latency for packets on the upstream and downstream. Cloonan said cable operators have a lot of interest in low-latency DOCSIS, and that it will probably be deployed first in North America. Low-latency DOCIS would require software updates to cable modems and legacy cable modem termination systems (CMTS).
"We're actually rolling it out as a deployable feature within the fourth quarter," Cloonan said. "It'll probably reduce 99% of the packet delays from hundreds of milliseconds down into the 10 millisecond range."
The road to 10G
As for 10G, Cloonan said it's a multi-step process going forward and that having the DOCSIS 4.0 spec finished in April was key to 10G. In the short-term, cable operators could get 10-Gigs down and 5-Gigs up before hitting the symmetrical 10G speed.
"We're working with the silicon vendors and the entire vendor community is working to try to get those DOCSIS 4.0 systems out the door in the 2023, 2024, 2025, timeframe," Cloonan said. "They (cable operators) can start deploying them and probably enable them a few years after that.
"10G is a road, it's a path and it's a journey."