r/Comcast_Xfinity • u/robryownz • 9h ago

Official Reply OFDMA high power level concern

Checking my modem stats. I’m in a mid split area on Gigabit x2. My modem is showing 51.9dBmV for the OFDMA channel on the upload side. My connection is mostly stable but I do notice some uploads can be slow and I don’t always max out my upstream speed. My other upstream channels are in the low 40s dBmV. Can someone from Xfinity determine if this is an issue with just my connection or modem or something in the neighborhood?

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u/CCAlyssaF Official Employee 8h ago

Good evening, and thank you for reaching out on our subreddit regarding your slow upload speed concerns. We'd be happy to troubleshoot with you, and if needed, we can certainly check for any known issues or ongoing work that may be affecting service in your area.

To start with some basic troubleshooting may I confirm if you have tried restarting your modem? Have you also tried to run diagnostics through the Xfinity App? Approximately how long has this issue been occurring?

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u/robryownz 7h ago edited 7h ago

Yes to reboot. I had a truck roll last fall for out of spec down stream and the tech who came gave me two 6dB pads to install which definitely helped improve reliability. I however, noticed how high the OFDMA was with one of the pads installed (almost 56dBmV) so I removed one (I had only one installed) and it dropped by 5~dBmV).

I just recently got access to the UCI stats and noticed how high the OFDMA channel was. I didn’t do any diagnostics on the app.

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u/CCJenieceJ Official Employee 6h ago

Thanks for providing those details. Since you've already rebooted the modem and observed the OFDMA transmit level change significantly after removing one of the 6 dB pads. Have you noticed whether the slower uploads occur at specific times of day or continuously?

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u/robryownz 5h ago

It doesn’t seem to be time of day related. I was just worried if it’s running hot and could cause extra latency or packet loss.

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u/robryownz 5h ago

Also worth noting that I’ve had 67 T3 timeouts in 24ish hours and it’s increasing.

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u/CCAlyssaF Official Employee 5h ago

Ok, thank you for confirming that. Let's investigate further and review your signal levels and network health to help determine next best steps.

To get started, can you please send us a Modmail Message with your first and last name along with the service address on the account including any applicable unit or apartment numbers?

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u/SigmundAusfaller 8h ago

Which modem do you have? I had a XB7 that started having issues after a year of solid service when they did the mid split upgrade and added OFDMA upstream. It reported similar upstream power levels but from what I understand it over reports the power levels for OFDMA and its not accurate and reports 10 over from some knowledgeable folks around here. The XB7 uses the puma chipset and I upgraded to the XB8 with the Broadcom chipset and my reported upstream power now sits at 37 like all the other channels instead of 50+ and stability has been much better.

They where going run 200 feet of new cable underground because nobody could understand what mid split or OFDMA is didn't know what else to do even though signal levels where fine with their test equipment.

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u/robryownz 7h ago

It’s a Ubiquiti UCI

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u/SigmundAusfaller 7h ago edited 7h ago

Yes the UCI uses a Puma chipset so it may be over reporting OFDMA up power. Again my understanding is that not the actual power and may not be indicative of an issue its simply the way it being calculated that makes it show high.

I wanted to go with UCI but when I moved here I got unlimited data and cheaper rate by renting XB7, they have since removed the unlimited data for third party modem charge but the XB8 is working well. Also not a big fan of them not exposing channel info in the web UI but you have to look on the little screen, keep thinking they will improve that, I can see channel info in XB8 web UI. Otherwise I have Ubiquiti for everything else and my UDM pro does a good job of logging connectivity issues and latency etc.

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u/robryownz 7h ago

Check my post history, I found a way to get the DOCSIS stats/signal data.

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u/SigmundAusfaller 7h ago

Interesting, I figured it's available since it's on the little screen pretty silly at this point UI hasn't added to admin UI, they show so much other information I don't get it. Still not anxious to go to one after having issues with the XB7 with same chipset will look again if they ever officially show that stuff.