DOCSIS 3.1 is already gunning for multi-gigabit speeds over HFC networks but a new project that will bring data symmetry to that platform and likely prolong the need to pull fiber all the way to the home, appears to be making swift progress.
CableLabs announced that project, called “Full Duplex” (FDX) DOCSIS, in February 2016, and it’s going to be a hot topic at this week’s SCTE/ISBE Cable-Tec Expo in Philadelphia.
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Rather than requiring a cable system to separate spectrum dedicated to the downstream and the upstream with a traditional “split,” FDX will enable “dual-use” bands for traffic that runs in both directions. FDX will also require an N+0, passive network, which fits in with the plans of some operators to pull fiber deeper and remove the active amplifiers present between the node and the home.
Following an initial feasibility/evaluation phase, the FDX project has since transitioned to the R&D and spec-writing phase. In August, CableLabs kicked off face-to-face meetings for the working groups and, if all goes to plan, is poised to become an extension to the DOCSIS 3.1 specs sometime in 2017, according to Belal Hamzeh, vice president of wireless technology at CableLabs.
FDX is an “evolution” of the current D3.1 specification, he said, noting that there will need to be some hardware modifications to existing gear. Whether that’s at the silicon or board level will be up to the specific implementations of the vendors.
There’s an expectation that existing DOCSIS 3.0 bands will not overlap with the FDX band, but those implementations will vary from one operator to another and perhaps even within the same operator, Hamzeh said.
Tom Cloonan, chief technology of network solutions at Arris, said spectrum allocation for an eventual migration to FDX is still an active discussion among MSOs and vendors.
However, a possible deployment scenario could see an MSO set aside a band for the legacy DOCSIS upstream (at 5-85 MHz or 5-100 MHz), another band for the legacy downstream (perhaps at 700 MHz to 1.2 GHz), with a band sandwiched in the middle (say, 100 MHz to 700 MHz) that’s dedicated to the FDX operation.
“There might be some variations there, but at a high level, that's the kind of spectrum some people are talking about,” Cloonan said, noting that FDX could be initially targeted to plant that has already deployed N+0 along with a move to remote/distributed architectures that move the PHY or the MAC and PHY closer to the edge.
Though the specs for FDX are still in flux, Cloonan said there’s some optimism that the technology could be ready by as early as 2018, but sees 2019 as the year when it sees its true heyday.
“There’s a force-function to make it happen quickly,” he said. “A very high level, there's an awful lot of interest in Full Duplex DOCSIS among the MSO community.”
Comcast is among the MSOs that’s shown interest in FDX.
“With Full Duplex, we’re witnessing the emergence of yet another powerful tool for delivering leading-edge speed and performance to Internet customers,” Dr. Robert Howald, vice president, network architectures at Comcast, said in a statement to Multichannel News. “We take an ‘all-of-the-above’ approach when it comes to providing choice to our Internet customers.”
Comcast has already launched D3.1-powered gigabit services in Atlanta, Nashville and Chicago, with Miami and Detroit among those that are already on deck.
“Full duplex is also an impressive reminder of both the flexibility and power of the Hybrid Fiber Coaxial model, and of the tremendous innovation that continues unchecked in HFC technology,” Howald noted. “The toolbox gets bigger and better every year, and our focus is on using those tools to deliver the best possible experiences to customers.”
FDX and a move to distributed architectures “could go hand-in-hand” as MSOs conceive their deployment strategies, Jeffrey Leung, director of product management at Casa Systems, said.
As operators go fiber-deep, “that will be potentially a perfect time to change,” he added. “In order to prepare yourself to go with these technologies, remote PHY will be a key requisite.”
Still, going with FDX or just taking that next step, and pulling fiber all the way to the home, is a point of debate.
"It becomes an interesting business case analysis that each MSO has to do individually, and the answer is likely to be different for each MSO,” Cloonan said, noting that Arris continues to make bets on both options. "We're a firm believer that DOCSIS has a long life ahead of it. We also know that PON has good life coming ahead of it as well.”
Cisco Systems is also placing bets on FDX. Last month, Cisco introduced a silicon reference design for Full Duplex DOCSIS alongside a pledge to contributing the design on a royalty-free basis to the cable industry in order to accelerate the speed of the technology’s development and eventual deployment.
Nokia, meanwhile, has also been keeping its fingers on the pulse of FDX. It demonstrated a prototype of the concept, calling it “XG-CABLE,” in May at the INTX show in Boston.
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