Arris S33 gigabit speed issues, upstream power low, Xfinity says it's the modem, Arris disagrees

I have an Arris s33 modem, and my download speed is capped at roughly 400 Mbps. When I first installed this modem, along with a new Wifi 6 network, I was getting regular download speeds of 800-900 Mbps. Then, after a day of no connections, and spotty internet, I am now stuck at speeds less than 400 Mbps. I have had a tech out to the house twice, they have replaced the line to my house, and have confirmed that my speed is definitly capped at 400ish Mbps with this modem. Line quality is "Excellent" according to the last tech visit. While at my house, the last tech called Xfinity while he was here, and even though my modem is "compatible" with their gigabit speeds, Xfinity said my modem was to blame for the slow speed. He said their response was to "try one of the Xfinity modems or another brand". So, I chat with Arris, and they said the upstream power levels are too low. I have one company blaming the other, and can't seem to get a straight answer as to why my speeds are so low. The modem is less than 3 months old, and other than trying another brand of modem, I don't know how to resolve this.

Upstream power levels are between 38 dBmv and 40.9. dBmv. Arris says they should be between 45 dBmV to 61 dBmV

So, is the upstream power really the issue, or is the Arris modem just not compatible with Xfinity Gig internet?

Responses

jeff7117

Regular Visitor

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3 Messages

4 years ago

To add to this post, my modem log is filled with these errors:

CM-STATUS message sent. Event Type Code: 24; Chan ID: 159; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 1.;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;

CM-STATUS message sent. Event Type Code: 16; Chan ID: 159; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 1.;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;

(edited)

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mike929

Frequent Visitor

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6 Messages

4 years ago

so, was this ever resolved? I have this modem and pay for 1200 download speed and don't even get half that - 200-280. I have replaced the cable modem thinking it was the issue and it did not resolve anything.

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S

sason

Visitor

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1 Message

4 years ago

I'm experiencing the same issue of only receiving 400Mbps while on a 1200Mbps plan. I'm also seeing the following messages in my modem's event logs:

24/5/2021 12:14:57	6	CM-STATUS message sent. Event Type Code: 16; Chan ID: 48; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 3.;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
24/5/2021 12:16:18	6	CM-STATUS message sent. Event Type Code: 24; Chan ID: 48; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 3.;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;

(edited)

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XfinityBrie

Administrator

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672 Messages

Hi there all. Below I've listed what are considered acceptable power levels for Xfinity.

• Downstream Power Level: -10dBmV to +10dBmV is acceptable for modems. -7dBmV to +7dBmV is the ideal range and is also the specified range for telephony modems.

• Downstream Signal to Noise Ratio (SNR): This number should be at least 35dB. Higher is better. Anything less than 35dB and you will probably have slow transfers, dropped connections, etc.

• Upstream Power Level: This should be between 35dBmV and 55dBmV. If your levels are beyond this range, you will likely see frequent disconnects or modem reboots.

• Upstream Signal to Noise Ratio (uSNR): Above 31dB is acceptable. Higher is better. Note: you will need to contact customer support to find out this value as it is not available via the cable modem status page.

• Upstream Receive Power: Ideally this number should fall within the -2dBmV and +2dBmV range. Note: you will need to contact customer support to find out this value as it is not available via the cable modem status page.

• In Channel Frequency Response (ICFR): The ICFR should be no higher than a 2dBmV. Note: you will need to contact customer support to find out this value as it is not available via the cable modem status page.

When testing speeds, we recommend doing so directly to the modem with an ethernet cable. If the speed coming from the modem are not processing in an acceptable range, a technician can double check the speed coming directly from the tap. If that speed is accurate, we would refer you to the device manufacturer for additional troubleshooting.

Using Approved Third-Party Equipment for Xfinity Internet and Xfinity Voice

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4 years ago

0

EG

Expert

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110.8K Messages

@ComcastBrie wrote: • Upstream Power Level: This should be between 35dBmV and 55dBmV.

I have found that the maximum upstream power is 51dB (like it used to be all along) before customers start having connectivity problems. 55 is out of spec ! Comcast has disabled the extended upstream power feature for modems a while back. That feature allowed for 55dB power levels.

I am not a Comcast Employee.
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4 years ago

U

user_994523

Visitor

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1 Message

4 years ago

Any resolution to this? I have same issue with S33 and Xfinity. The back and forth blame game is causing me to explore dumping both Arris and Xfinity.

1

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EG

Expert

•

110.8K Messages

@user_994523

Please create a new topic of your own here on this board detailing your issue. Thanks. 5-month-old dead thread now being closed.

I am not a Comcast Employee.
I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.

Was your question answered? Please mark an Accepted Answer! tick

4 years ago

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Your Home Network

jeff7117

Arris S33 gigabit speed issues, upstream power low, Xfinity says it's the modem, Arris disagrees

jeff7117

mike929

sason

XfinityBrie

EG

user_994523

EG

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