The Docsis Addendum

8:30AM -- A few more details are circulating about Docsis 3.x, a purported annex to the current Docsis 3.0 specs that will take a long-term look at enhancing cable's skinny upstream path. The effort may also begin to stoke a fight between Cisco Systems Inc. (Nasdaq: CSCO) and other incumbent cable modem termination system (CMTS) vendors and Broadcom Corp. (Nasdaq: BRCM), with its new idea that aims to bring PON-like speeds to hybrid fiber/coax (HFC) networks.

Cisco execs hinted at the Docsis updates last week, but, so far, CableLabs isn't saying much, only that it is "continually looking at emerging technologies and updates to our specifications including the Docsis 3.0 specification." Cisco, meanwhile, issued a statement on Friday clarifying that it had merely "advocated for the creation of a new version of the Docsis specifications." (See The Cable Show 2012: To Docsis 3.0 & Beyond! and Cisco Hints at What Comes After Docsis 3.0.)

But they're all up to something, whether it ends up being called Docsis 3.1 or something else. Another Docsis vendor (we won't say who because it appears that CableLabs is trying to suppress talk of any new work around D3) confirmed there is some sort of Docsis 3.x project afoot, while a different source indicated that it's also being labeled under the acronym of ARM, though I haven't been able to track down what it stands for yet.

But they're both in the same neighborhood, with the discussion largely centering on higher frequency modulations (for example, 256QAM or 1024QAM) to generate more bits per hertz, while also lifting the current cable upstream ceiling -- perhaps to 200MHz or 300MHz.

I was helpfully reminded that Docsis 3.0 already defines 64QAM and offers some bandwidth expansion via the inclusion of the "mid-split," a bandwidth remapping procedure that would expand the upstream to 5MHz-85MHz from the current 5MHz-42MHz. There doesn't seem to be a lot of interest in a "Top Split," which would put additional upstream capacity above 1GHz, which, I'm told, would be extremely painful to deploy and would require a hefty guard band that would end up wasting 100MHz or more of spectrum. (See CableLabs Eyes a Super-Sized Upstream .)

Upstream of the future
And what is under discussion now takes a very long-term, phased approach to cable's upstream, because, I'm also told, the mid-split should give cable enough upstream capacity -- in 1GB spurts with sustainable links of 100 Mbit/s -- to last a decade or more based on future upstream traffic projections, at least for residential services. "The mid-split should not be looked at as a temporary band-aid," a source says.

Now, this is also being discussed as the Institute of Electrical and Electronics Engineers Inc. (IEEE) works on a new standard called EPON Protocol Over Coax (EPoC). While some engineers have claimed that EPoC can live harmoniously with Docsis and the emerging Converged Cable Access Platform (CCAP) architecture, there seems to be a battle brewing behind the scenes about which approach will push cable forward -- will it center on enhancements to Docsis, or this EPoC project that originated out of Broadcom? (See Countdown's on for EPON Protocol Over Coax and The Case for EPON-Over-Coax & CCAP Coexistence.)

And some of that tension may spill out at The Cable Show this week. We hear that this tech panel -- "The Gigabit Network: New Possibilities in HFC" -- on Tuesday will present details of a jointly developed whitepaper from Arris Group Inc. (Nasdaq: ARRS), Cisco and Motorola Mobility LLC (all competitors, mind you) that offers some vendor alignment on whatever this Docsis 3.x idea is (although I doubt they'll label it as such) or at least to offer the industry a recommendation about how to proceed. That recommendation's also expected to offer some veiled (or outright) resistance to EPoC, which could threaten their hold on the cable access market.

And based on how this shakes out, we'll learn who has more power here -- one of cable's primary silicon suppliers or its key OEM partners. Of course, what the cable operators want will trump all, but it certainly tees up what's sure to be a feisty debate in Boston this week.

— Jeff Baumgartner, Site Editor, Light Reading Cable

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