Upstream bandwidth has always been the Achilles heel of cable networks. But since bandwidth demand is so heavily weighted in the downstream direction, the industry has largely ignored the problem in favor of extending downstream capacity to accommodate gigabit- and multi-gigabit-per-second speeds.

Now Comcast Corp. (Nasdaq: CMCSA, CMCSK) is ready to reevaluate the situation.

Speaking on a panel at Gigabit Cities Live, Vice President of Network Architecture Robert Howald acknowledged that he expects Comcast will look to solve the upstream challenge with more spectrum.

"There's a limit to what you can do in 5-to-42," said Howald, referring to the spectrum range currently used for upstream bandwidth. On the other hand, by extending that spectrum range to 85MHz, he added, "[you] can do multiple hundreds of megabits speeds."

Hundreds of megabits isn't the same as a gigabit, but Howald questioned whether gigabit capacity is really needed in the upstream. He seemed to suggest that a mid-split at 85MHz might be enough upstream expansion, and that a higher split at 200MHz -- which some operators in Europe are considering -- would be overkill. Howald added that Comcast crunches the numbers regularly to try to determine when and where expanding the upstream could make sense. (See Comcast Puts DOCSIS 3.1 Live in the Field.)

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Cox Communications Inc. 's Senior Access Architect, Ony Anglade, was less definitive than Howald. Asked about going with a mid-split, Anglade said "It's part of the analysis." But he added that Cox hasn't made a decision.

Meanwhile, Comcast and Cox continue to make progress with DOCSIS 3.1 development, which they plan to use as a supplement to fiber-to-the-home rollouts for delivering downstream gigabit speeds. As has been previously stated, Howald confirmed that 2016 will be a big year for commercial DOCSIS 3.1 deployments at Comcast. (See Comcast Preps 2-Gig Service… Over Fiber.)

Anglade noted that Cox is likely to go into major deployments in 2017. And Gerry Ford with Interactive Broadband Consulting Group LLC (IBB) predicted that mid-market operators will likely follow suit in 2018. In the near term, one of the big challenges for DOCSIS 3.1 deployments is finding ways to test new D3.1 equipment. However, CEO Cyrille Morelle of testing company VeEX Inc. said that his company is preparing to be ready with new tools for a DOCSIS 3.1 field trial in August.

"There's a myth out there that you need fiber to do a gigabit, and that's just not true," said Howald referring to downstream network capacity.

Getting to gigabit speeds in the upstream is another story, but extending the spectrum range to 85MHz may still get HFC networks as far as they need to go.

— Mari Silbey, Senior Editor, Cable/Video, Light Reading