FDX/Unified DOCSIS

fmd · 2025-02-13T20:05:09+00:00

While we wait for the announcement that N+X deployment has officially begun... Unified is the new version of FDX that has downstream going all the way to 1.8 GHz (currently limited by old taps). The return still stops at 684 MHz. Comcast has presented this spectrum layout to begin with: This is sufficient to offer symmetrical 2 Gbps. When more of the legacy channels go away, higher speeds can be offered. 3.1 modems that get FDX-L (limited) firmware can use the FDX channels.

videomatic3

CommunityMember I always punch in the neighbors address that doesn’t have comcast. Easier to find promotional pricing. Reddit solved everything this morning at 4am. They are great.

badtlc4

videomatic3 That seems to be the only reliable Xfinity support location.

kirkyg

smilingbob
Yea this is listening to customers and transparent simple pricing structure to comcast sigh. I was finally given the option to select 5 year pricing in mid splits area, was only allowed to upgrade from 1gb to 2gb plan to lock in that price, and at the end of the process i can see in my account says the ‘contract’ price will expire in 5 years. Its the same game just pricing more aggressively in the near term because they are losing customers so fast their head is spinning.

Greed will be the downfall of this company…

kmax

kirkyg Yeah, back when I dumped the phone and tv because they wouldn’t offer me a promo. That was during the height of ARPU days. Hell I was quad play. They couldn’t do anything.

So dropped phone,tv. Backed the internet down to 800 or whatever. Then waited a month and hit reddit up and then they were able to give me a promo because there was room to move up from 800 to 1000. Talk about games, and they lost a few hundred in recurring monthly revenue during the process.

fmd

CableLabs has published the updated revision of 4.0 that includes “Unified”, so it’s now officially in there.

hex0101

fmd So if Comcast wants to deploy 1.8 Ghz FDX instead of 1.2 Ghz FDX, will they need all new amps/LE’s and several years to swap out the amps again? XB10 does appear to support 1.8 Ghz. Not sure if it can use FDX up to 1.8 Ghz or only 1.2, with 1.3-1.8 being standard downstream/upstream channels only.

I imagine this will become more important over time as Comcast decides to roll out faster speeds or add capacity to the network as customers use more bandwidth. 8K streaming, etc. Think 10-15 years ahead from now.

cypherstream

hex0101 they already have to hit up every amp, le and node again for regular FDX after just putting in mid split. They just overbuilt a lot of our area with brand new mid split stuff just to have to hit it up again at some point.

That’s the advantage of HFC. Never ending work. Jobs, jobs, jobs.

fmd

hex0101 The 1st gen FDX hardware only goes to 1.2 GHz, but 2nd gen (Unified) goes to 1.8 GHz. XB10 supports Unified, so it is required to support 1.8 GHz in FDX mode.

kirkyg

hex0101 8k will never be a thing. Pixel density is too tight for humans to reasonably sit close enough to tvs to watch content in 8k. 4k is it with any existing technology we know today.

hex0101

cypherstream Wouldn’t surprise me if mid split areas sit for a few years while sub-split areas go directly to FDX today.

MacLeech

cypherstream That’s the advantage of HFC. Never ending work. Jobs, jobs, jobs.

Telecom is like road work, it’s always never ending work. Always a need for more bandwidth, in more locations. Backhoes, squirrels, car accidents, and fires.

It’s all good though, it’s kept me employed and busy for over a decade. I don’t see the upgrades for any of it, especially fiber, ending anytime soon. All that edge capacity needs backhaul.

SpottedCat

cypherstream

cypherstream they already have to hit up every amp, le and node again for regular FDX after just putting in mid split.

I’m surprised they put the effort in to upgrade to mid-split and didn’t just put in the amps that would be able to handle FDX down the line. Did the amps just not exist at the time?

My node was upgraded to mid-split in 2023, which wasn’t even that long ago.

Man-of-Leisure

cypherstream That’s the advantage of HFC. Never ending work. Jobs, jobs, jobs.

Meanwhile, most fiber is already doing 8Gb on XGS-PON now

Google Fiber is doing 20Gb on 25G-PON now

Ziply Fiber is doing 50Gb residential using some type of Ethernet over fiber, since 50G-PON wasn’t available yet.

Meanwhile, Comcast is slowly upgrading to 2Gb with 250Mb upload lol

Man-of-Leisure

MacLeech Telecom is like road work, it’s always never ending work.

Fiber much less so.

Upgrading from GPON to XGS-PON to 25G-PON to 50G-PON is far easier, cheaper, and faster than all of these DOCSIS upgrades.

That’s what’s scaring the cable companies. Once the fiber is in place to compete with them, it can be upgraded with faster speeds much more rapidly than the cable companies can respond.

Cable is just now finally rolling out 2Gb speeds in response to 2Gb which has been available on fiber for many years now. Fiber has already moved on to 8Gb and beyond now, while cable is still trying to catch up to 2Gb.

It could be another decade until DOCSIS is doing 8Gb widely at this rate.

hex0101

SpottedCat FDX amps were still being tested in the lab in 2023, the first N+0 node with FDX went live in September 2023. There was still a long way to go.

CommunityMember

SpottedCat I’m surprised they put the effort in to upgrade to mid-split and didn’t just put in the amps that would be able to handle FDX down the line. Did the amps just not exist at the time?

My node was upgraded to mid-split in 2023, which wasn’t even that long ago.

Note that one of the large parts of mid-split, DAA nodes and vCMTS[0], prepares for a potential (if the equipment and techs are available, and both are going to be constrained for a while) to move more quickly to FDX.

I believe that someone posted in the old DSLR that some plants took the opportunity to swap older amps and housings for Starlines (and especially if they were going to have to replace the amps anyway because they were not able to support mid-split frequencies) so those housings would be FDX ready (once it was known the Starline housings were going to be the target).

[0] Which is a huge change (and sometimes consolidation of locations) of the headend equipment.

cypherstream

SpottedCat A press release came out in our local newspaper in May 2022 that Comcast was going to expand into our township, and we were one of the first subdivisions to get it. Funny because I moved here in 2010 and when I left my apartment I told Comcast I was sorry to leave because they just did this huge HD channel expansion and I was beta testing 100mbps docsis 3 at the time.

From May 2022 to late 2024 Comcast did a lot of new overbuilding and edge out expansions. But in 2022 when the conduit was being put in, FDX amps didn’t exist. They also didn’t do Node+0 or FTTH, despite spending all that labor right then and there. The last mile is the hardest to get to all fiber, but in our greenfield when the ditch witch was out and all the conduit was going in… they just didn’t want to use that as an opportunity.

I do think its Node+2 though. Theres MB-120’s and BLE-120’s along with 3 Harmonic nodes in my development. Two populated power supplies and one Power supply cabinet they placed but nothing in it.

Meanwhile my operator SECV is doing FTTH. In fact I saw a fiber tap in front of an Italian restaurant we like. A tech I know for them says my area should get the fiber lit in 2026.

SpottedCat

hex0101 Wow, things move faster than I thought. Hopefully Comcast is willing to upgrade their infrastructure again so soon.

CommunityMember

hex0101 FDX amps were still being tested in the lab in 2023, the first N+0 node with FDX went live in September 2023. There was still a long way to go.

And the first field test[0] of a prototype FDX amp was not until September-ish 2024. Production quantities of the FDX amps and associated equipment for wider deployment were not expected until early 2025 (and even then, the supply will be constrained for quite some time).

[0] Lab testing is an important step, but nothing compares to being deployed in the field, where the most interesting things are encountered (in theory, the lab testing over the decades has improved to simulate the known/expected field impairments, but people in white coats are not the same as real plants). The old adage has always been that in theory, theory and practice is the same, and in practice, it is not.

videomatic3

SpottedCat
I think they planned to and are upgrading so quickly

kirkyg

videomatic3 only reason is because until they have fdx they don’t have a competitive product with att fiber. The funny part is the fiber hw only needs new termination equipment and cpe to exponentially expand toward 25g. It’s a tough road ahead for docsis.

kmax

Man-of-Leisure Meanwhile, Comcast is slowly upgrading to 2Gb with 250Mb upload lol

They are in panic mode I imagine. Warms the heart.

hex0101

Man-of-Leisure Ziply Fiber is doing 50Gb residential using some type of Ethernet over fiber, since 50G-PON wasn’t available yet.

This is cool, basically since every home has their own fiber strand back to the PFP, Ziply can change a home’s fiber strand over to Ethernet for 10 and 50 Gig customers (dedicated fiber), and change it back to PON for 5 gig and below speed tiers. No outside plant changes needed in the neighborhood, you only need extra fiber from the CO to be available at the PFP.

kirkyg

Man-of-Leisure docsis dYs are numbered.. The only thing that’s working for them is near term use cases for 10+gbps are few. It’ll take some years before we can use all that bandwidth at scale.

swilliams

Man-of-Leisure It could be another decade until DOCSIS is doing 8Gb widely at this rate.

What’s the physical ceiling of RG6? Is 8Gb even physically possible?

badtlc4

Man-of-Leisure Fiber upgrades are actually costing MORE than companies were expected. at&t, verizon, GF have all run into this uncomfortable reality.

Stuff

Man-of-Leisure You state that fiber has moved on to 8Gb and beyond. Can you please let Verizon know this? They only are offering 1Gb in my area so Comcast Xfinity wins with 1.2Gb in the advertising space.

Man-of-Leisure

swilliams What’s the physical ceiling of RG6?

It just carries RF signals, so whatever frequency they can achieve without signal loss.

swilliams Is 8Gb even physically possible?

Yeah, DOCSIS 4.0 supports up to ~ 9.5Gb down, ~ 6Gb up with ESD at 1.8GHz downstream, 684MHz upstream.

But that requires shutting off QAM TV entirely, and moving everything to OFDM/A.

CableLabs mentioned they’ve already tested 3GHz, and even 6GHz and beyond, which would support download speeds of 25Gb, 50Gb, and more.

It’s likely that the higher frequencies would only work well over shorter distances, so it may end up requiring Node+0 or eventually fiber to the tap.

badtlc4

swilliams RG-6 doesnt really have a known hard limit. It is really about signal processing and how far you can go with certain speeds. There are data centers that can pump terabit/s through RG-6.

fmd

swilliams Ron Hranac talks about top frequency vs attenuation in this article: https://broadbandlibrary.com/the-untapped-capacity-of-coaxial-cable/

Two takeaways: 1) Coax can go pretty high (actual frequency response must be measured). 2) You don’t get both. Increase the top frequency and you lose on distance, and vice versa.

Capacity… That depends on the modulation. It may be lowered on very high frequencies to deal with the high signal loss (one way to deal with 1.8 GHz, depending on amplifiers and the spacing between them).

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