Comcast speed test shows 4Gbps upsteam and downstream over cable

Comcast, the largest U.S. provider of gigabit broadband Internet services, has demonstrated internet speeds greater than 4 gigabits per second (Gbps) in both directions over a cable network.

The test was conducted on Broadcom’s full duplex DOCSIS 4.0 chip, which will support future multi-gigabit upload and download speeds. By full duplex, it means that the upstream speed is the same as the downstream speed. Normally, most people can get access to a gigabit per second download speeds, but uploading crawls at maybe 20 megabits per second.

The test is part of Comcast’s long-term plan to reach 10G, or 10 gigabits a second full duplex, over its hybrid-fiber coaxial (HFC) network. The HFC network uses the blazing fast fiber-optic network technology as well as coaxial cables that come into our homes.

Supported by the research arm of the cable industry, Cable Labs, Comcast is creating its 10G Platform as a multi-year, global technology initiative that will dramatically increase speed and capacity over HFC networks. During the pandemic, this kind of internet speed is critical, as Comcast saw its traffic rise 32% in 2020.

Behind the trial

Above: Comcast has been laying a lot of cable.

Image Credit: Comcast

This trial begins to lay the groundwork for network operators like Comcast to deliver multigigabit download and upload speeds over  connections that are already installed in hundreds of millions of homes worldwide. Cable operators in the U.S. have already installed networks that pass 85 percent of U.S. homes.

The Broadcom chip is expected to become the world’s first production silicon to be developed using the DOCSIS 4.0 Full Duplex standard, which represents an evolutionary leap forward in the ability to deliver ultra-fast speeds over HFC networks. One of the most important breakthroughs in the DOCSIS 4.0 standard is the ability to use network spectrum more efficiently, allowing operators to dramatically increase upstream speeds without sacrificing downstream spectrum to do so, Comcast said.

A key advantage of DOCSIS 4.0 Full Duplex is that it establishes a foundation for operators to deliver multigigabit speeds over their existing networks to the connections already in hundreds of millions of homes around the world, without the need for massive digging and construction projects.

Comcast technologists in Philadelphia and Denver conducted the test by installing the Broadcom SOC in a simulated network environment to track the performance of its Full Duplex DOCSIS features – including echo cancellation and overlapping spectrum – which combine to support substantial improvements in network throughput. In the test environment, the research team demonstrated the ability of the system-on-chip (SoC) to deliver upstream and downstream throughputs of greater than 4 gigabits per second (Gbps). Future optimization is expected to drive even greater capacity.

Comcast’s vision

Above: Inside Comcast’s CTC in Philadelphia.

Image Credit: Comcast

Elad Nafshi, senior vice president of next generation access networks at Comcast Cable, said in an email to GamesBeat that the performance of the Broadcom chip exceeded expectations. He said the SoC was built by Broadcom, and the test was designed and executed by Comcast network engineers in Philadelphia and Denver, with the support of technology partners at Broadcom.

“More broadly speaking, the developments we’re seeing today on 10G are the result of global collaboration between operators, technology makers and standards bodies,” Nafshi said.

Last October, Comcast technologists were able to deliver 1.25 Gig symmetrical speeds over a live, all-digital network by leveraging advances in Distributed Access Architecture, Remote PHY digital nodes, and a cloud-based virtualized cable modem termination system platform (vCMTS).

Even as Comcast works to test and deploy Full Duplex DOCSIS to enable multigigabit upload and download speeds in the future, the company is leveraging the technologies from the October trial, along with DOCSIS 3.1 in the upstream, to increase speed and capacity in the near term. In my area, I can pay for a gigabit downstream connection.

“Comcast has been working to develop the technologies that power 10G since well before it was formally introduced in January 2019,” he said. “[We] played a key role, along with industry partners, in developing the DOCSIS 4.0 Full Duplex standard. The lab test itself was the result of several weeks of construction, preparation and design by Comcast network engineers in Philadelphia and Denver.”

He added, “We don’t have any news to share at this point about new product and service offerings, but we’ve been excited and impressed by the pace of innovation with technologies like distributed access architecture, virtualization and DOCSIS 4.0. We’re very confident that the mix of speeds we make available today are more than fast enough to meet and exceed our customers current needs. We’re continuing to move forward with testing and development of this technology, because we know the future will bring even greater demand, and we want to be ready for whatever comes.”

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