Does Docsis Have a 10-Gig Future?

Jeff Baumgartner
LR Cable News Analysis
Jeff Baumgartner, Senior Editor, Light Reading

BOSTON -- The Cable Show -- Engineers from Arris Group Inc. (Nasdaq: ARRS), Cisco Systems Inc. (Nasdaq: CSCO) and Motorola Mobility LLC have joined forces to refresh cable's Docsis platform and put it on a path that, they claim, could achieve a capacity of 10Gbit/s in the downstream and 2Gbit/s in the upstream.

That would blow the latest generation of Docsis 3.0 technology out of the water. Here at the show, Intel Corp. (Nasdaq: INTC) is previewing its new Puma6 family of chips, including a "media gateway" configuration that bonds 24 downstream channels and eight upstream channels -- enough to produce speed bursts of almost 1Gbit/s downstream and 320Mbit/s upstream. (See Intel's New Docsis 3.0 Chip Guns for 1-Gig .)

John Chapman, the CTO of Cisco's cable access business unit, presented the ideas here Tuesday, offering a condensed version of a 182-page paper co-authored by the vendors, which compete in the market for Docsis cable modems and cable modem termination systems (CMTSs).

The paper's stated aim was to give the cable industry recommendations on how to develop a new generation of Docsis as cable operators start to migrate all of their services to IP.

But there's a bit more to the agenda, as the vendors also have a vested interest in protecting their hold on the Docsis equipment market as other potential technical options begin to emerge, particularly EPON Protocol Over Coax (EPoC), an Institute of Electrical and Electronics Engineers Inc. (IEEE) standard in the works that's looking to bring PON-like performance to hybrid fiber/coax (HFC) networks. (See The Docsis Addendum and EPON-Over-Coax Starts Its Standards Journey .)

The Docsis vendors listed out 10 areas of consensus that, they believe, could start to redefine Docsis and create a roadmap that would enable the platform to achieve the kind of speed performance that EPoC is also shooting for. Here are a few ideas in which Arris, Cisco and Motorola are in agreement:

  • Define backwards compatibility as a goal that will let current Docsis cable modems and next-generation Docsis modems use the same spectrum.
  • To start beefing up cable's skinny upstream path using a "mid-split," a process that would expand cable's usable upstream spectrum from today's range of 5MHz to 42MHz, to 5MHz to 85MHz. Longer-term, the new specs would also define a "high-split" that would expand the upstream even further -- perhaps up to 400MHz.
  • On the downstream side, the vendors suggest operators manage that spectrum using tools like switched digital video (SDV) and H.264 and upgrade to 1GHz. Longer-term, they suggest operators raise the ceiling to 1.7GHz.
  • Move to higher orders of modulation (4096 QAM or more) that will increase the number of bits that can be transmitted on the cable plant.

Chapman didn't take any direct shots at EPoC, but did call Docsis "the most successful Ethernet-over-coax technology to date."

And he argued that Docsis can be molded into something that can handle cable's future performance requirements, so long as the industry agrees to commit to a new roadmap and set to work on it soon. "Docsis can be anything the Docsis community wants or needs it to be," Chapman concluded.

— Jeff Baumgartner, Site Editor, Light Reading Cable

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