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.

fmd

meerkathalon The power levels seem valid, so the modem is seemingly able to range on the channels (they are not being blocked), but elevated noise could prevent further communication.

Talking about levels… jsterling’s FDX upstream is 11-15 dB lower than the regular upstream. That seems odd. 🙂

Did you ask them for the fix, or did it just get applied?

crucialcolin

bigcoda did they ever complete the work on your street?

It seems like all they were doing in my neighborhood was a replacing old doughouses. They did the same throughout much of Roseville, CA in fact. I haven’t seen crews working at all in the city for at least two weeks now. Even the in house Xfinity maintenance techs I sometimes see around have disappeared. I now doubt they were working on FDX prep but just fixing some stuff (Better housing ventilation, couple node splits, etc) to better match Xfinity’s current mid-split standards.

Then the big FDX node I saw crews installing on Pleasant grove blvd was actually for road construction(The city is widening the roadway). So that explains that activity. Xfinity had to relocate their equipment first. It was probably faster/less downtime for crews to install all new vs actually moving everything that had been in place.

videomatic3

meerkathalon
youre probably maxing out the 4 atdma and 1 ofdma channel, nice.

Moffetts

crucialcolin If you’re referring to the node strapped to a telephone pole, that was an NC4000 and Comcast doesn’t even use those for midsplit.

crucialcolin

Moffetts If you’re referring to the node strapped to a telephone pole, that was an NC4000 and Comcast doesn’t even use those for midsplit.

No this was a brand new Commscope node being put into position for a large Amphenol ground doughouse to fit over it as I was driving down the blvd. It was kind of neat watching them work while I was stuck in traffic. All of our utilities are already underground in my city.

bigcoda

crucialcolin did they ever complete the work on your street?

Nope, it’s been real quiet around my area for the whole month of August. Some of the little flags, that they use to mark the underground utilities, went missing at one of the old amp location. I’m assuming the homeowner removed them, when they cut there grass? I’m hoping they didn’t forget my street, and activity will pick up after labor day weekend. Exactly three years ago in September, was when they replaced the nodes for Mid-Split, keeping my fingers crossed. The area about four block over, were the replaced the nodes & amps. Went back to showing Mid-split speeds, after initially dropping to Sub-Split, after the upgrades.

crucialcolin

bigcoda Exactly three years ago in September, was when they replaced the nodes for Mid-Split, keeping my fingers crossed. The area about four block over, were the replaced the nodes & amps. Went back to showing Mid-split speeds, after initially dropping to Sub-Split, after the upgrades.

Yeah it was the same time frame for me with the mid-split upgrade completed in 2024.

I’m not holding my hopes up for FDX since all activity ceased in the area and I haven’t gotten any network upgrade notices yet. There also hasn’t been any routine overnight maintenance either of late which in of itself is a bit weird. But anyways I figure any FDX upgrade would come early this September otherwise they will wait it out another year. Time is now running out.

jsterling

meerkathalon

So when they first rolled out the FDX all 4 OFDMA locked fine and then 3 of them just stopped working like 2 months later. Since I had a local escalation contact due to the downstream issues I reached out to him and a line tech came and messed with the node for a few hours but it still didn’t lock and then they performed some non-physical maintenance overnight a couple days later and it resolved it.

I noticed the power levels on my upstream being super low on the OFDMA as well as they were always like that and they said that’s normal. Upload has never really been an issue in this FDX adventure, it’s been the downstream. Even the band-aid is crap in my opinion. The fact that if you reboot it takes a minimum of 12 hours for the band-aid to return seemingly but the speeds barely reach 2Gig and I’m seeing uncorrectables which would indicate the band-aid just isn’t that stable.

hex0101

MAINTENANCE FINALLY FIXED MY SIGNAL LEVELS

Previous Levels
Upstream was 54.5 TX on the QAM’s, and 48.8 on the OFDMA.
Probably changed the tap value, no more 26 value!

Still have the signal loss from the splitter, so these signals at the modem are really good!
Being directly connected to the plant would increase things to +4.0-4.8, and I could get the upstream down another 4db. Actually would be similar on the downstream side to what I had before on sub-split with analog optics and the minibridger.

No AT&T crews today at least nearby, be funny in both companies ran into each other. Would have happened had Xfinity swapped this tap value on Wednesday.
They did tell me by the end of the month, PON will be live.

Hopefully the next few taps down the line (rear easement) are not running with too low of signal.

All done with plant modifications!
Back to normal status!

No minibridgers/line extenders (amplifiers) were added to finally address the signal levels. Tap value swap most likely! There was another outage about 50 minutes after the tap swap though. Could have been swapping tap values at the node/further upstream from my tap or adjusting tilt on the RPD.

fmd

hex0101 So the total power is now ~60 dBmV. The “FDX goal” is to not exceed 55 dBmV (total) for the channels below 85 MHz. You will be close to that without the splitter.

Edit, to elaborate. The modem has a power budget of 65 dBmV (both 3.1 and current 4.0 modems). The goal is to use max 55 dBmV for the legacy upstream and 64.5 dBmV for the full duplex upstream (65 dBmV when you add them). These numbers are also used by the specification.

The legacy upstream may use more, but it has to steal it from the full duplex upstream.

meerkathalon

meerkathalon Well, the tech they sent today was an absolute waste of my time. The first thing he says is “symmetrical is fiber only”. I said, no this is FDX. He wasn’t even familiar with it and was insistent that I don’t have it.

He plugged his tool into the plate and speed tested it. Then shows me that the upload speed is 450 and says “see it’s not here”. Never looked at the spectrum or the channels.

cypherstream

meerkathalon wow they don’t even train their techs? Not the first time those of us on the forum know more than the employee.

hex0101

meerkathalon He plugged his tool into the plate and speed tested it. Then shows me that the upload speed is 450 and says “see it’s not here”. Never looked at the spectrum or the channels.

XM2 Signal meters are only DOCSIS 3.1, so the tech was testing mid-split. XM4 meter is DOCSIS 4.0. XM2 meter was the stop-gap solution, as it is DOCSIS 3.1 High-Split capable.

meerkathalon

Like I said, the first thing he told me was “symmetrical is fiber only.” I explained no, I have it on my plan. He then checked his tablet and saw my account reflects 2000/2000 Mbps. After I explained that it’s FDX, without even looking at the settings, he insisted “that’s not installed here yet.” Dude basically showed up, ran a quick speed test, and left. Zero effort put into checking which channels were locking or unlocked. I legitimately knew more than this guy. I can see the 3 unlocked OFDMA on the freaking modem but he didn’t even look at it on his device.

cypherstream

meerkathalon I hope you aren’t charged for the service call. If you are, fight it on Reddit support.

hex0101

cypherstream eventually with enough tech visits to your premises within a 30 day period, a supervisor is supposed to be dispatched instead. I think the threshold was 3 tech visits within a 30 day period. 3rd visit would have been a supervisor.

These days, I’m not sure how things are done.

Moffetts

meerkathalon The pitfalls of being on the bleeding edge… I had similar struggles after mid split was rolled out and the techs just not getting it.

bigcoda

crucialcolin But anyways I figure any FDX upgrade would come early this September otherwise they will wait it out another year. Time is now running out.

Exactly three years later in September, looks like Comcast is going to start rolling out FDX network upgrades on my street. Apparently crews must have had snuck in, and replaced one of the amps down the street on Friday, when I was at work. I didn’t notice it till Saturday, because a car was blocking the amp. The other two doghouses further down the street, with the underground utilities marked. Which I assume have amps in them also, still haven’t been touched. From what I’ve been seeing, any time they upgrade to the new CommScope amps, around Stockton. They also swap out the whole doghouse, with one of these new taller ones, compared to some of the old ones around Stockton. I have pictures of the old vs new doghouse, I’m not sure what brand these are? Comcast also sent me a Email, confirming there are going to be doing upgrades in my area on Monday September 14. Hopefully you will see some action in your area, now that Labor is over.

crucialcolin

bigcoda nice!

Yeah that’s a different housing for sure. I wouldnt know what it is. Typically Comcast uses either Amphenol or Channel Communications housings but maybe they have a third supplier in some areas.

So far no emails for me. Nothing is marked on any of the streets anymore since they changed out a bunch of housings / did prep for a node split(which may be changed over by now). I would assume they would remark everything if they were going to come back through to swap amps? Also there are still some line extenders in place throughout various portions of the neighborhood that’s not already on FDX. It’s also only been two years between first receiving mid-split upgrades and now here. I wonder if they will wait for three years here as well 🤔

bigcoda

crucialcolin Yea It’s hard to tell what Comcast is doing, when it comes to these Mid-Split, and FDX upgrades sometimes. They seem to be all over the place, and do things different from one area to another. You got some areas that went straight to FDX from Sub-Split, and other areas that haven’t been touched, still on Sub-Split. And some people reporting they have the FDX nodes & amps in place for two years, but only have Mid-Split available.

I currently only have the 300 Mbps plan. But it’s going to be interesting, if these old Taps from the 80’s and 90’s can handle the 2 Gb symmetrical speeds, that some people will have in my neighborhood. My drop from my house to the Tap is also pretty old. I think the last time it was replaced, was in the late 90’s or early 2000’s? My original drop from my house to the tap, was dual RG59 from the A/B switch days.

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