Cable Internet with download and upload speeds of 10Gbps may eventually come to American homes thanks to a new specification for higher-speed, symmetrical data transmissions.

The industry's R&D consortium, CableLabs, today announced that it has completed the Full Duplex Data Over Cable Service Interface Specification, an update to DOCSIS 3.1. The completion of the 10Gbps full duplex spec comes 18 months after the project was unveiled.

The completion of the spec doesn't mean you'll suddenly be getting multi-gigabit uploads and downloads, as commercial deployments may be at least a couple of years away and may not initially provide the maximum speeds allowed by the spec.

The initial version of DOCSIS 3.1 was announced in 2013 and allowed 10Gbps downloads and 1Gbps uploads, but the first modems weren't certified until early 2016, and real-world implementations are still catching up. Comcast last year began offering gigabit download speeds over cable using DOCSIS 3.1, but the service limited uploads to 35Mbps. Comcast's only symmetrical gigabit service uses fiber-to-the-home instead of cable, as fiber technologies have supported symmetrical transmissions at gigabit speeds for years.

While the maximum speeds enabled in specifications are often years ahead of commercial offerings, CableLabs described the full duplex spec as a major breakthrough.

"Current DOCSIS networks have to juggle available upstream and downstream traffic," CableLabs Research and Development VP Belal Hamzeh wrote in the announcement. "Full Duplex DOCSIS technology supports multi-gigabit symmetric services by enabling concurrent transmissions in the same spectrum, providing the ability to increase the upstream capacity without sacrificing downstream capacity. This has the potential to greatly improve network efficiency and, in turn, customer experience."

The full duplex version of DOCSIS 3.1 "offers high speeds over the existing infrastructure and is less expensive to deploy than fiber, while still maintaining backwards compatibility with previous generations of DOCSIS technology," Hamzeh wrote.

Symmetric, multi-gigabit cable services possible in 2019

There are still a few more steps before commercial deployment, an article in Multichannel News explains. While the physical layer (PHY) spec is completed, the media access control (MAC) layer is being developed in working groups and will be completed "in the near future," Hamzeh said, according to the article.

The PHY layer completion signals that full duplex has reached the "'advanced maturity stage,' enabling vendors to push ahead with their product development," Multichannel News wrote.

If product development goes as expected, "operators could start deploying the technology commercially by the end of 2019," Light Reading reported in August.

We asked Hamzeh what kinds of equipment upgrades customers will need to take advantage of the update to DOCSIS, and we'll provide an update if we get one. Last year, Hamzeh wrote that CableLabs' "design and analysis shows that the existing Physical and MAC layer protocols in DOCSIS 3.1 technology can largely support this new symmetric service."

But that doesn't mean you'd get 10Gbps out of an existing modem. Cisco demoed a proof-of-concept in May, with a downstream rate of 890Mbps and upstream of 680Mbps. Cisco explained that the ultimate goal with full duplex is to use 576MHz of shared spectrum, but "today’s cable modems 'top out' at an upstream spectral location of 204MHz," of which 96MHz was used in the demo.

When contacted by Ars, CableLabs said customers will need "a Full Duplex DOCSIS modem in the household" to get symmetrical 10Gbps speeds. Cable companies will be able to use "existing coaxial infrastructure," but will also need a full duplex-capable "remote PHY or remote MAC PHY node," CableLabs said.

The Nokia-owned Bell Labs said in May 2016 that it achieved 10Gbps symmetrical cable speeds in the lab using a slightly different system that it calls XG-Cable.