DENVER –Racing to deliver symmetrical multi-gigabit speeds over its HFC networks, the cable industry is moving quickly to craft a next-gen version of its DOCSIS broadband standard for introduction as early as sometime next year.
Formally known as Full Duplex DOCSIS 3.1, or FDX, the forthcoming tech spec is designed to support data speeds as high as 10 Gbps in either direction. It aims to make use of a technology called "echo cancellation" to allow upstream and downstream signals to travel over the same spectrum at the same time.
Speaking at the SCTE/ISBE Cable-Tec Expo show in Denver late last month, industry technologists said FDX will enable cable operators to stay ahead of the slow but steadily growing consumer demand for faster upstream speeds. Technologists said FDX will also provide operators with a way to compete with the “billboard” gigabit speeds that telcos and other rivals with fiber-to-the-home networks are marketing heavily today.
“I think the biggest fear that the operators have is that their competition may one-up them and offer 1 Gbps service" when cable operators are still "limited to 50 Mbps upstream or 100 Mbps upstream,” said Tom Cloonan, CTO of network solutions at Arris. Noting that the cable industry's average upstream speed is now only about 100 kbps, he argued that the ability to deliver upstream speeds of 1 Gbps or more will allow operators to fight back against FTTH providers already offering upstream speeds of 500 Mbps to 1 Gig.
In the early going, industry experts believe that cable operators will more likely leverage FDX to meet the higher upstream demands of business service customers, but, by embracing the forthcoming spec and moving in that direction now, operators could also future-proof their networks for residential services and earn the biggest bang for their buck, said John Chapman, a fellow at Cisco Systems and the CTO of the company’s cable access business.
“If you’re going to spend money on the plant…do you do a small upgrade, or do you do a big upgrade?” Chapman asked on a show panel with Cloonan. “Ideally. you spend the money on the plant once and it lasts for a long time.”
Chapman noted that cable operators could choose to perform a "mid-split" on their plant spectrum, which would mean increasing the available upstream spectrum limit to 85 MHz, or about twice as high as it is now. Doing just that would free up enough spectrum to permit increasing upstream speeds to as much as 400 Mbps, high enough to meet short-term consumer needs but not likely long-term customer demands.
“It’s not going to be a 10-year plan,” Chapman said. “It’s going to get tight at some point in time.”
Instead of going the mid-split route, cable operators could also push the upstream spectrum bar to 204 MHz, which is often referred to as a “high-split.” That would enable operators to offer upstream speeds of more than 1 Gbps to their broadband subscribers.
But Chapman noted that such a move would also require dramatic changes to the HFC plant. So, he argued, if a cable operator has already made the commitment to switch out such basic network devices as diplexers, amplifiers and return path amps, why not just get ahead of the curve altogether by taking the next logical step and putting in place a real next-gen frequency plan for the upstream?
“It negates the need to go to fiber [to-the-home].” – John Chapman, Cisco
“What more bang for the buck could you get for that?” he said. “We have Full Duplex lined up for that. It will have built-in future proofing…it negates the need to go to fiber [to-the-home].”
In addition, Chapman sees cable operators pairing FDX technology with such other next-gen access network strategies as Fiber Deep to compete with FTTH rivals. Under the Fiber Deep approach, operators are pushing fiber lines much further into their HFC networks, enabling them to remove all the active electronics devices and drastically reduce the size of their customer service groups. In turn, they are replacing each existing fiber-optic node with 12 to 18 nodes and new distributed architectures. “It’s like a package deal,” Chapman said.
Equipment suppliers like Arris and Cisco now have a technical path forward for products that will support FDX in the future, thanks to preparatory work by CableLabs. In early October, the cable R&D group issued the critical physical layer specs for FDX, just over a year after beginning the spec writing process. Belal Hamzeh, VP of research and development, wireless technologies, for CableLabs, said the release of the physical layer specs indicated that the FDX spec has reached the “advanced maturity stage,” allowing equipment suppliers to go forward with actual product development.
The more optimistic industry experts predict that cable operators will begin FDX field trials sometime next year and continue them into 2019, with significant deployments starting in 2020. The Cable-Tec Expo show featured demos of FDX-facing technologies and products from a number of major vendors. The list included what Cloonan termed an “early stage demo” from Arris and more advanced demos from Cisco, which previously showed off how the echo canceller technology will work.
