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Need my upstream fixed; Arris S33; slow upstream (30 vs 300Mbps)
Had Xfinity install internet service yesterday, everything is working good except my downstream speed is slower than expected. I'm on the 2Gbps plan with rated speeds of 2000 Mbps down, 300 Mbps up. My average speed test results are showing 2,330 Mbps downstream and only 31 Mbps upstream.
The technician that performed the installation yesterday hooked up his equipment in place of my modem and he got 311 Mbps upstream, showing that the issue is with my modem configuration/internet profile. The technician said that a ticket would need to be opened to have this issue investigated further to have my profile/configuration updated, etc.
Modem is an Arris S33 that is certified for Xfinity and supports up to 2.33 Gbps - it provides 32x SCQAM/2x OFDM for downstream channels; 8x SCQAM/2x OFDMA upstream channels.
My modem's configuration is showing full utilization of the downstream channels, however the upstream is being limited to only 4x SCQAM bonded channels. Support online suggested that the power levels are also a bit low for my upstream (averaging 40-41 dBmV) and should be at least 45 to 51-60 dBmV (range depending on number of channels).
I've performed numerous resets, factory resets, reconnections, etc. Still getting the same results from speed tests directly from the modem wired (2.5Gbps Ethernet).
Any help with this issue would be greatly appreciated!
Accepted Solution
BruceW
Gold Problem Solver
•
26K Messages
1 month ago
The upstream power levels are fine. Arris' recommended levels are, to use the technical term, crazy.
The S33 modem is compatible with 2 Gbps internet speed, but is not compatible with the new higher upload speeds. Only a few retail devices are. See the "Next Gen" list at the top of the "All Compatible Devices" link near the bottom of https://www.xfinity.com/support/devices (at the moment it points to https://assets.xfinity.com/assets/dotcom/projects/cix-4997_compatible-devices/2024.09.18%20Full%20List%20of%20Compatible%20Devices.pdf, but this changes from time to time).
Also see:
For faster upload you need one of Comcast's newer rental gateways (XB6, XB7, XB8) or one of the few retail devices shown in the "Next Gen Speed Tier" group with an upload speed rating in the "All Compatible Devices" PDF:
The Reddit link (if they ever get the page back online) lists the approved devices (although that list is out of date) as well as other requirements for faster upload speeds.
Realize that although Comcast calls some devices "Compatible" and some "Recommended", for all but a few devices those designations only mean "compatible/recommended for use with their Internet service", and not necessarily approved for the new upload speeds.
Comcast could make all of this much simpler and clearer, but they have chosen not to do so.
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