CableLabs Eyes Multi-Gigabit Upstream for HFC

‘Full Duplex’ Tech Will Bring Data Symmetry to DOCSIS 3.1
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DOCSIS 3.1, cable’s next-gen IP platform for HFC networks, originally targeted capacities of 10 Gbps down by at least 1 Gbps upstream, but a new “Full Duplex” approach aims to close that gap and enable MSOs to deliver symmetrical multi-gigabit broadband -- without having to make the leap to fiber-to-the-premises (FTTP) technology.

CableLabs said it considered wireless Full Duplex technology to enable symmetrical IP capabilities during the early days of DOCSIS 3.1 specs development, but determined then that it was not yet ready for prime time. Fast-forwarding to today, and the cable R&D group believes it has developed a Full Duplex-based approach that will allow DOCSIS 3.1 to evolve to support the technology and boost upstream capacity by 10 times.

CableLabs unveiled a Full Duplex DOCSIS technology last week at the organization’s Winter Conference in Orlando, according to this blog post by two CableLabs execs --  Belel Hamzeh, VP wireless, R&D, and Dan Rice, SVP, R&D.

"Our design and analysis shows that the existing Physical and MAC layer protocols in DOCSIS 3.1 technology can largely support this new symmetric service," they wrote.  When operating in Full Duplex mode, cable’s upstream and downstream traffic “use the same spectrum at the same time, doubling the efficiency of spectrum use," they explained. 

Existing technologies, they said, typically use either Frequency Division Duplexing (FDD) or Time Division Duplexing (TDD). Via FDD, for example, upstream and downstream traffic operate separately in dedicated parts of the spectrum. In today’s DOCSIS networks, the lower portion of the spectrum is dedicated for upstream, and the upper portion is used for downstream. As for TDD, the upstream and downstream traffic share the same spectrum, but take turns using it – as WiFi or DSL does today.

“A DOCSIS 3.1 Full Duplex network provides the peak speeds and flexibility of TDD solutions, but one-ups both TDD and FDD with double the capacity,” the CableLabs execs wrote.

The Full Duplex approach envisioned for DOCSIS will use a combination of passive HFC and the self-interference cancellation and intelligent scheduling that's present in DOCSIS 3.1.

“Its approach significantly increases upstream data capacity in order to enable symmetric multi-Gigabit broadband data services for consumers and the enterprise,” they wrote. “These developments are expected to yield DOCSIS 3.1 network performance of up to 10 Gbps symmetrical on 1 GHz HFC networks, with the potential for even higher performance by utilizing spectrum that is currently available for future expansion above 1 GHz.”

As an “incremental evolution” of DOCSIS 3.1, it will also be backward compatible and coexist with previous-generation DOCSIS network deployments, they claimed, noting that Full Duplex DOCSIS is a prime example of a “CableLabs 2.0” vision that’s focused on innovation projects.

Among next steps, CableLabs will work with a team made up of members and vendors to help the industry further validate and mature the technology.

Nbn, a government-owned entity tasked with bringing next-gen broadband to millions of homes and businesses in Australia that will use D3.1 for the HFC portion of its gameplan, praised the development.

“Although it is still very early days the arrival of Full Duplex DOCSIS 3.1 is extremely exciting news for nbn and a real game-changing moment in the ultra-fast broadband market,” Dennis Steiger, CTO of nbn Australia, said in a statement. “We will be working closely with CableLabs to track the development of this technology and are excited about the potential this offers for the 4 million premises that will receive their nbn services via our HFC network.”

He noted that it’s only been possible to deliver multi-Gigabit symmetrical broadband using FTTP, but the new Full Duplex development means “HFC is now right up there in terms of being able to deliver these kinds of speeds.”

This video posted by CableLabs sheds more light on the Full Duplex DOCSIS initiative: