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.

Aceq2jot

@“fmd”#p126902Ii had an un announced outage last night and my OFDM is 900 Mhz and SC-QAM channels start counting from 387 MHz.. I am hopeful but my speeds tanked.
UPDATED: I have had speed troubles and resrted the modem then checked online and saw i was upgraded.

computerman2

Finally had to get Comcast Xfinity Reddit to help me obtain Mid-split upload speed, but got it now! all it took was one back end code to be added.

Working Great so far

Now just wait and see if and when in the future FDX arrives

fmd

Aceq2jot And only the one OFDM? Have you received the fix that adds more SC-QAM channels?

cypherstream

Aceq2jot Odd the speeds tanked until you rebooted the modem. They should have the ability to reboot the modems for you. Like why not use PNM to see which modems are not operating optimally after a maintenance event and send a single reboot in the middle of the night?

Tshirt

cypherstream They should have the ability to reboot the modems for you.

The fact that it didn’t reboot may indicate they weren’t finished, believed a restart was not needed (yet), or that his modem didn’t hear the reboot message.
they might have been waiting to fire up a second OFDM channel before a mass reboot.

Aceq2jot

fmd I gained a bunch SC-QAM channels. Sadly the XB10 I had took a dump so they sent me an XB8 then yesterday morning there was a reboot at 3 am of my modem. Noticed speed issues so I checked my speed on the website. The funny thing is they cant seem to see my modem as the phone app says i have two gig x 2 gig but cant find a modem and when i look online at some pages it says i am not an internet customer. I uploaded the plan speeds and my logs are below.

Aceq2jot

Tshirt It did reboot itself at 3AM according to the uptime in the log yesterday. I am on the phone with tech support and am getting an appointment to get an XB10 from the store. That is confirmed that I am on 2×2 and need a new modem which I will pick up. It is odd as from what i read on here i was expecting to see the amps disappear but the new amps they hung earlier this year are still around. 2 amps between each white node. with this being my amp one block from the FDX Node and then there is one at the other end of the block.

Moffetts

Why did you think the amps would disappear?

hex0101

Aceq2jot It is odd as from what i read on here i was expecting to see the amps disappear but the new amps they hung earlier this year are still around.

These are FDX amps already!

Only time you will see an amp disappear is when a node split is performed. Even then, not all of the amps will disappear in pretty much every case.

Aceq2jot 2 amps between each white node.

Sounds like the plant is split very well already.

Aceq2jot

Moffetts previous posts talking about Node+0. People not getting FDX until the amps disappeared. I generally read through the threads and look at what the more knowledgeable have posted so I don’t post something that has been covered. Also i have been told in previous threads that the amp pictured was not FDX capable by some members. But needless to say I thought it would happen soon as we have CenturyLink fiber and T-Mobile Fiber are going gangbusters in my area, so competition is good and I am glad I was grandfathered in on my price.

hex0101

@fmd

SNR improved.

System Uptime: 2 days 1h: 54m: 33s
Zero Uncorrectables.
Signals look clean.

All time high for me on the downstream SNR!

Moffetts

Aceq2jot It is certainly not standard procedure to take an N+2 (for example) plant and migrate it to N+0. Comcast tried this back in 2018ish in certain places and it apparently was not scalable or economical. Some new builds are N+0, and obviously some converted N+0 areas exist, but the entire point behind the R&D efforts behind the FDX amps was to allow FDX performance without redesigning existing plant for N+0.

cypherstream

hex0101 Weird all the downstream channels show XXX MHz, then you get to that OFDM and its like “90000000”.

Must be vibe coded.

meerkathalon

Aceq2jot Good luck! I’m curious to see if your XB10 will lock to all four of the OFDMA channels (or if you will have the same problem myself and others have reported).

The additional DS channels showing up after 24hrs is super odd. I wonder how that works on the backend. It would be funny if it is some cron script they had to throw together temporarily.

Moffetts

cypherstream To be fair, the OFDM channels have always shown up that way.

Aceq2jot

Sorry I did have pics but it did not upload them so here they are. Upstream and Downstream. I am picking the new modem up later this afternoon.

Update: The Xfinity webpage is all over the place showing I have two gateways. So I asked CoPilot and this is what it gave me and said that the XB10 will provision everything.

Why the XB8 causes this exact mess
The XB8 is a DOCSIS gateway.
Your new plan (2‑gig X2Gig) is an X-Class / FTTP / ONT-based tier.

When Xfinity tries to map an ONT-based plan onto a DOCSIS gateway:

The system adds a dummy gateway (the phantom second device you’re seeing).

The account may show no internet plan because the gateway profile doesn’t match the plan code.

The app may show your XB8 as offline even when it’s working.

Speed provisioning becomes inconsistent or capped.

This is a known behavior inside their provisioning system.

I
have two

Aceq2jot

Moffetts Thank you.

fmd

hex0101 All time high for me on the downstream SNR!

It’s pretty. You have higher SNR than me now.

I can’t remember who it was, but someone showed 50 dB using XB10. I think he is leading the SNR club 🙂

Aceq2jot

Here are the new logs from the XB10. Upload speeds are now around a Gig and Download speeds are around 1.5Gig. The app says i need a tech so i have an appointment T

uesday.

hex0101

Aceq2jot Watch for those extra D3.0 QAM’s, they may show up. You will know as the download speed will then hit closer to 2 Gbps.

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