Broadband

High Times for DOCSIS 3.1

Comcast Says D3.1 OFDM Signals Working Well at Higher Modulations 3/10/2016 6:15 PM Eastern

Denver -- The DOCSIS 3.1 era is still in its early days, but results from the initial trials are showing that the next-gen platform is fully capable of running at higher modulations, where MSOs can pump out more bits per hertz and deliver services in a more bandwidth-efficient manner. 

 

Comcast has been testing OFDM signals on all types of plant types as it gears up for D3.1 deployments to see how higher-order network signals (1024 QAM and 4096 QAM, for example) behave, and the news so far is good.

 

“What we found is that these signals do propagate through the network very well,” Jorge Salinger, Comcast’s VP of access architecture, said Thursday at the Cable Next-Gen Technology Strategies event, put on here at The Cable Center by Light Reading.

 

That’s also been true on HFC plant that run “long cascades” of amplifiers. In many locations, Comcast has been able to run 4096 QAM without any problems in many locations, he said, noting later that DOCSIS 3.1 trials have shown verified support for multiple modulation profiles, rather than having to support the lowest-common denominator.

 

Combined, those findings should be welcome news for MSOs that intend to use DOCSIS 3.1 to deliver gigabit broadband services over HFC.

 

“Our objective is to start deploying gigabit service using DOCSIS 3.1 this year,” starting in the downstream, Salinger said, noting that 2015 was about “network readiness” for D3.1.

 

He also reiterated Comcast’s stated plan to deploy D3.1 in Atlanta and Nashville in first half of the year, and follow with launches in Chicago, Detroit, and Miami in the second half of 2016.

 

Liberty Global, meanwhile, is also taking a close look at D3.1, but its use of 8MHz-wide channels with DOCSIS 3.0 (North American DOCSIS uses 6MHz-wide channels) lets it get to 1-Gig (in the downstream) with DOCSIS 3.0.

 

The impetus to launch D3.1 for Liberty Global isn’t as great as it might be for some U.S. MSOs, but “we are in deep, deep analysis of 3.1,” Bob Greene, managing director, online entertainment at Liberty Global, said, adding that the MSO has issued RFPs for DOCSIS 3.1.

 

The shift to D3.1 is also gaining lots of attention from the test and measurement vendors. Viavi, for example, just launched a field-test unit for the new specs. VeEX has six products in production or in prototype form that support D3.1, said its president and CEO, Cyrille Morelle.

 

Though 2016 is largely seen as a year of trail and exploration for D3.1, the adoption curve “will go gangbusters” in 2017, predicted Rob Flask, Viavi’s  director of product line management.

 

Casa Systems, a maker of CMTS and CCAP network gear that expects to play a key role in D3.1 rollouts, is also seeing trial activity pickup this year, but also sees 2017 “as a big year for DOCSIS 3.1,” said Jeff Leung, Casa’s director of product management, cable products.

 

The concept for Full Duplex has been around for years, but its potential application to the cable industry is new.

 

Theoretically, Full Duplex would eliminate the need for cable operators to split the spectrum used for upstream and downstream because they could use the same spectrum for both types of transmissions. That could eliminate the need for MSOs to perform a mid-split or a high-split to allocate more spectrum to the upstream.

 

Salinger said the potential presented by the Full Duplex concept should not change operator plans to do spectrum splits. It’s simply too early to know if the technology will work as advertised when applied to D3.1.

 

“We’re not sure how complex it would be to implement,” he said.

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