The Case for EPON-Over-Coax & CCAP Coexistence

DENVER -- Cable Next-Gen Broadband Strategies -- Cable's access network may be taking different angles on how to address the future demands of residential and business services, but cable engineers insist that those efforts -- Converged Cable Access Platform (CCAP) and EPON Protocol Over Coax (EPoC) -- will be complementary, not competitive.

EPoC is "definitely complementary" to CCAP, said Jorge Salinger, Comcast Corp. (Nasdaq: CMCSA, CMCSK)'s VP of access network architecture, last week. "EPoC gives us an alternative to having to deploy fiber to every premises." His remarks come at the 1:49 mark in the video below.

While CCAP is a super-dense device that combines the functions of the cable modem termination system (CMTS) and edge QAM to help put all of cable's residential services under the IP umbrella, EPoC is a budding IEEE Communications Society standard that aims to bring PON speeds to hybrid fiber/coax (HFC) and primarily target business-class services. (See EPON-Over-Coax Starts Its Standards Journey .)

Comcast has already issued a request for proposal for CCAP equipment as it prepares for some small-scale deployments later this year. (See Comcast Issues CCAP RFP .)

John Chapman, a Cisco Systems Inc. (Nasdaq: CSCO) fellow and CTO of the company's cable access business unit, said during his keynote that Docsis still has plenty of gas in the tank and uses different components, but agrees that EPoC and CCAP should play nice together because they addresses different market opportunities although they will live in different neighborhoods on the cable frequency spectrum. "It's really a usage scenario," he said. (See Does Docsis Have a 5-Gig Future? )

A CCAP device will be capable of taking in Ethernet and outputting Docsis or PON. "EPoC gives us a simplistic view on how to approach the network at the edge," Cox Communications Inc. Senior Director of Network Architecture Jeff Finkelstein said in a panel last week.

Bright House Networks has been deploying EPON for business services since 2006, and is hopeful that EPoC will give that decision some extra legs as the MSO looks to deliver big bandwidth in areas not served by fiber.

"We are already doing EPON, so it makes sense to have options there," said John Dickinson, senior director of network strategy and architecture at Bright House. "EPoC lets you place fiber where you need it, and leave coax in other areas."

Dickinson is also keen on EPoC because its goal is to become a worldwide standard that will help drive equipment prices down as volumes ramp up.

But it's still early days. While CCAP is nearing its first deployment cycle, the same for EPoC likely won't be said for at least a couple of years. [Ed. note: We'll have an update on EPoC's progress at the IEEE soon.]

— Jeff Baumgartner, Site Editor, Light Reading Cable

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Mr Finance 12/5/2012 | 5:38:07 PM
re: The Case for EPON-Over-Coax & CCAP Coexistence So what is this tech really? given the term EPON refers to optical and this is seemingly still delivered over coax the term seems to be entirely marketing. Is there at least any sharing of upper protocol stacks with telco epon standards and more importantly what are the physical layer tricks used v the latest docsis variants. Are these tricks (that will mainly drive chip costs) substantially faster, cheaper or more spectrum efficient than next gen docsis standards. If not then what does this tech have going for it other than a hyped and seemingly incorrect name?
Jeff Baumgartner 12/5/2012 | 5:38:05 PM
re: The Case for EPON-Over-Coax & CCAP Coexistence

When boiled down, this is about trying to modulate EPON signals on coax, with the stated goal of providing symmetrical 10Gbit/s speeds over HFC networks. The cable guys want it because they would like to deliver PON speeds to businesses without always having to pull fiber all the way to the premisis. This is coming out of the IEEE EPON standards group, but I'd have to check with them to see if there's any sharing of upper protocol stacks, or ask someone from the EPoC working group to chime in here. JB



msilbey 12/5/2012 | 5:38:04 PM
re: The Case for EPON-Over-Coax & CCAP Coexistence

Interesting. I hadn't even processed the fact that they're going through the IEEE first.

Regarding the goals of EPoC, sure it makes sense to aim for more speed without dragging fiber end to end, but the engineering feats to make EPoC work - and in conjunction with traditional residential services as you say - must be monumental. It's surely not simple or elegant, and the efforts at optimization seem to grow more complex every day. At some point I wonder when the complexity has to fold in on itself and create new problems.

But - in the meantime, MSOs are saving money and keeping cable engineers employed. Can't argue with that. 

Jeff Baumgartner 12/5/2012 | 5:38:04 PM
re: The Case for EPON-Over-Coax & CCAP Coexistence

I still view RFoG as a niche, nice to have option for new housing developments or plant extentions in rural areas. It was a nice thing to have when builders insist on fiber, but the housing market went in the tank. Plus RFoG doesn't offer much in the way of a speed increase...it's nice and clean, but it  replicates Docsis, VoIP and RF video services on fiber while letting the MSO preserve the backoffice, headends and use of the traditional CPE gear l(set-tops, cable modems/EMTAs, etc.).

  Guess I'm not as confused about one of the primary  goals of EPoC -- to bring  PON speeds to businesses over existing HFC networks and avoid the expense of pulling fiber all the way to the premises. The trick will be  coexisting with all those residential services that also occupy other portions of cable's spectrum. Guess they could go end-to-end PON someday, but then you're talking about a lengthy transition because there's a significant non-PON legacy infrastructure that will serve customers for years and years to come.  But, you're right, EPoC will give HFC more legs, if they can make this work. We'll see... it's still pretty early (the working group is still defining the objectives of EPoC)  and I think BRCM has only produced some prototypes of what's in mind  here. But I think they are doing right by trying to make this a global standard via the IEEE at the get-go, versus starting it at CableLabs and then working it through the SCTE and then onto the IEEE. JB

msilbey 12/5/2012 | 5:38:04 PM
re: The Case for EPON-Over-Coax & CCAP Coexistence

It is rather confusing. We had RF over glass and now modulation of EPON signals over coax. With all the effort spent trying to make different delivery protocols and access networks work together, it's a wonder nobody throws up their hands and just does end-to-end PON. 

And yet, cable continues to make HFC work. While buying itself more and more time to make a shift that seems perpetually 5 years down the road. 

msilbey 12/5/2012 | 5:38:03 PM
re: The Case for EPON-Over-Coax & CCAP Coexistence

Ah yes, I've heard rumblings that some MSOs are looking at spectrum above 1 GHz. So far I believe Cox is the only major operator to go even that far. 

Note too that the upstream is shown only in the 5-42 MHz range, despite discussion of extending that up to 85 MHz. Hmm.

Jeff Baumgartner 12/5/2012 | 5:38:03 PM
re: The Case for EPON-Over-Coax & CCAP Coexistence

You are right about the complexity... even when you consider just&nbsp;the potential spectrum planning that it would involve.&nbsp; This is just an example deployment scenario, but here's how EPoC and cable's&nbsp; legacy services *could* coexist on the same swath of spectrum: <img alt="" height="171" src="http://img.lightreading.com/2012/01/216207/9174.jpg" width="500">

(image source: IEEE)

Interesting that this example shows activation of spectrum well above 1GHz. JB

Jeff Baumgartner 12/5/2012 | 5:38:02 PM
re: The Case for EPON-Over-Coax & CCAP Coexistence

You are right about that... upstream is pretty thin right now and there's nowhere enough to go around for all of this as-is; But, as you stated,&nbsp;MSOs are starting to look at mid-splits and even top splits to help open that up a bit... and I don't recall any of those scenarios &nbsp;being anything less than messy. But necessity is the mother of invention, as they say. I just wonder how long we've got before&nbsp;this becomes a real&nbsp;necessity. &nbsp;JB



Duh! 12/5/2012 | 5:38:02 PM
re: The Case for EPON-Over-Coax & CCAP Coexistence

See the note.&nbsp; "This is one illustrative example of spectrum provisioning.&nbsp; There are many other examples...."

But to the point, there is a difficult conundrum here.&nbsp; Upstream bandwidth is a limiting factor, especially for more symmetrical services.&nbsp; Yet the high/low split at 42-55 MHz is embedded into every passive and every active in the network and in the premises.&nbsp; If you go to an 85 MHz high/low split, you're replacing everything except the coax.&nbsp; If you add upstream bandwidth above a GHz, legacy actives and passives will be able to coexist, but filters become much more complex.

No easy answers.&nbsp; But keeping cable engineers employed is definitely a good thing.


msilbey 12/5/2012 | 5:38:01 PM
re: The Case for EPON-Over-Coax & CCAP Coexistence

My understanding is that a lot of the products coming out are now supporting 5-85 MHz for the upstream. I wonder how quickly those products will fill the landscape as operators upgrade hardware for other reasons. &nbsp;-- and here I acknowledge that I know just enough to be dangerous.&nbsp;

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