Not sure if anyone can help me. My home internet keep flapping several times per day for years. I am using Rogers modem CODA-4582U. Originally I think it's modem issue, so I changed it from Rogers, things still the same , I start to use Rogers router as modem and bough ASUS AC 5300, same thing, then I bought AC3100， still the same thing. I am wondering if any professional can take a look to see if something wrong with signal below, much appreciated your help.
@zhouzhilong can you delete the data above the Downstream Overview please, as well as the numerical string following the "CM-MAC=xx.xx.xx.xx.xx.xx" address, which is the modem's MAC address.
Looking at the signal levels, looks like you have a noise issue as some of the DOCSIS 3.0 channels are running at 64 QAM instead of 256.
The OFDM channel, which this modem runs is situated in the 300 to 500 Mhz range. Did you copy the entire table all in one go? If so, then the modem isn't running the OFDM channel as it should be, so the modem would be relying on the upper DOCSIS 3.0 channels for the downstream data.
The upstream DOCSIS 3.0 channels are a little low, but, the measure of success is whether or not those upstream channels are satisfactory when they arrive at the Cable Modem Termination System, which controls and provides data services to the modem. Those numbers aren't reported back to the modem, so the end user has to call tech support to determine if the upstream channel signal levels and signal to noise ratios are adequate at the CMTS.
If you don't have one OFDM Downstream channels running, then you have signal problems in the 200 to 500 Mhz range. If thats the case call tech support and ask the Customer Service Rep to run a signal check on the modem. Don't reboot the modem prior to the call. Leave it exactly as it is. With the OFDM channel not running, that signal check should fail automatically. My guess would be that the modem is attempting to use that OFDM channel and failing those attempts due to the cable signal issue within the OFDM frequency range, falling back on the upper DOCSIS 3.0 channels which also have signal problems. Any noticeable drop in performance is probably occurring at the start of the attempt to use the OFDM channel, followed by a switch back to the DOCSIS 3.0 channels.
Advise the CSR that you don't have a DOCSIS 3.1 OFDM channel running and that you have some DOCSIS 3.0 channels running 64 QAM instead of 256 QAM. Those channels are located around 590 Mhz. So, what ever the problem is in the 200 to 500 Mhz band is going as high as 600 Mhz. That should grab the techs attention and force him or her to actually look at the data instead of relying on a simple go / no go check.
There simply isn't enough data presented to be able to understand what the problem is in that 200 to 600 Mhz band, so, you will need a tech to check your external cable and connectors. An automatic failure of the signal check should result in the CSR arranging for a tech visit at your convenience to resolve the problem.
When that is done, can you repost that entire table, from the Downstream Overview title, all the way to the bottom of the bottom OFDM/OFDMA section.