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A little background first - my COX account is for 500 Mbps, and with the Gateway speed tests on the COX website were somewhat greater than 500 Mbps.  However, we experienced daily issues with the WiFi, having to reboot the Gateway at least once almost every day.  Our laptops and other devices would lose connection frequently. 

So, I recently replaced my COX Panoramic Gateway with an Arris SB8200 cable modem connecting to a TP-Link Deco X55 (AX3000) mesh system (3 nodes).  The setup was easy and our devices don't seem to have any issues connecting.  However, download speed tests (WiFi) are now showing 80 Mbps (upload ~11 Mbps).  A wired test with my laptop connected directly to a Deco node showed only a slightly higher download speed of 85 Mbps.

According to COX my modem was provisioned properly and it all looks good on their end. 

So I sent a detailed report to TP-Link support, including all information they requested (various speed tests, network topology, firmware version, etc.).  They responded the same day with:  "Unfortunately, we can assume that your modem might be the one causing unstable and speed issue to your Deco and other devices.”   They also indicated that because a speed test conducted with the laptop directly connected to the modem via cable showed less than 100 Mbps, then my laptop could only accommodate up to 100 Mbps speed.  This of course completely ignored the fact that previous speed tests using the same laptop were 500 Mbps or greater.

As for the SB8200 modem, the lights have always showed the following:

Power:     Green

Receive:  Blue

Send:       Green

Online:     Green

The TP-Link Deco "home” unit is placed right next to the modem.  A second unit is two rooms away (~25 feet), and a third is downstairs at the opposite end of the house from the modem (~55 feet).

I read in a similar post in this forum that any splitters should be removed from the coax cable.  A splitter was added to the line coming into the house for a small TV (currently not connected).  Please note that the measured download speeds prior to the splitter being put on the line were the same as I'm seeing now.  

From the Web Manager, the values for the Downstream and Upstream bonded channels fall within the acceptable ranges. 

I'm at a loss as to what to do now.  Any assistance would be greatly appreciated.

 

Thanks!

 

 

Hello mdcleary76

                              Thank you for the clear and brief explanation on the issue. Basically, Slow speed, intermittent connection or no internet access occurs usually out of cable signal level, out of acceptable range and it will be resolved after the power level are adjusted by the service provider. So for this we need to check the cable signal level to confirm what causing this issue to proceed further.  There are some important things that should be within a specific range in order for the internet to work properly.

First, the SNR should be above 33 on all of them.

The downstream power should always be between -15 and +15. The closer to 0 the better connection.

Finally, your upstream power should always be between +45 and +51

On all of those values you should not have more than 3 decibels (or dB) between the lowest and the highest

By having the values in less than that, your device will have interrupted connection, slow or no connection at all. 

                       The lights on the modem are proper but the Send: Green and Green: Upstream channel is connected in DOCSIS 3.0 mode.
                                                                                                                                      Blue*: High-speed Internet connection with upstream channels in DOCSIS 3.1 mode.

Blue - Indicates DOCSIS 3.1 operation (high-speed Internet access) which may not be available in all location.  Check with your service provider for availability in your area. 

So just confirm with your Internet service provider to check on this and if still same issue you can take a tech visit from your service provider to check the lines using test modem.


 

 

The following describes the range of values for the Downstream and Upstream Bonded Channels for my  modem.

  • SNR values range from 39.7  to 41.1     So all values are above 33, and there are 1.4 decibels between the lowest and highest values.
  • Downstream power ranges from -2.2 to -5.1     There are 2.9 decibels between the lowest and highest.  So the downstream power is between -15 and +15

            *** Note that there is one downstream channel that is different from all the others, and is listed last. It has a channel ID of 159, Modulation is shown as “Other”, Power is -1.1, SNR is 40.8 dB. 

  • Upstream Power is +48.0  or +49.0 for all four channels.

 

So, except for the one odd channel,  all of the values are within the proper ranges.

 

 

 

 

An actual screensnip is easier to read. 

Also, when you connected the pc directly to the modem, did you check to see if the connection was at gigabit speeds? To often I see a sketchy cable between modem/router or modem/pc that defaults to the 10/100mbps speed and not gigabit. 

I’d check that. 

As well as when the deco is connected that its connected at gigabit speeds. 

The SB8200 has two ports, one of which is connected to the "main” deco unit.  If I connect my laptop 2nd directly to the second port (brand new cable), I get even slower download speeds (~50 or so Mbps).  The light on this port blinks yellow, so that indicates it's at 10/100.   If I instead connect it directly to the main deco unit, I get up to about 95 Mbps.  This is somewhat more than I get wirelessly (usually around 90 Mbps or so). 

My laptop is 10 years old, so of course my network adapter is not the latest tech, so perhaps I shouldn't expect too much. 

Even so, I still don't understand why when I was using a COX gateway (modem & router combined), a speed test run on the COX website showed over 500 Mbps.  Now it's showing numbers in the low 80's at best. 

Anyway, I appreciate the responses.  Also, here is a screenshot of the status:

 

 

I still don't have a solution for this.  I went to COX a few days ago, and everything looked right from their end.  I received an email today asking me to select the "best answer”,  but I'm afraid I haven't found the answer yet.  I managed to get my download speeds up a bit by buying a USB WiFi dongle (since my computer is old), but it's still not where expected.  If I ever get it figured out I'll post it here.

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