we operate several IOT connected machines that use a Teltonika RUT240 router with Olivia wireless simcards. With several machines now I have had issues with the mobile internet connection. We are running the routers with the 00.01.14.4 firmware.
Just this morning I was installing a machine with a sim card. Everything worked the way it was supposed to, the router provided internet via the sim card.
Half an hour later, the router was unable to connect to the internet. The router web interface showed that it was unable to receive any signal (0 dB). Between the mobile internet connection working and not receiving any signal, nothing was changed on the system. The location was still the same. I checked the antenna connection and router settings. All was in order. The apn is set according to the provider instructions. Rebooting the router did not fix the issue.
After running out of ideas, I replaced the sim card with another one by the same provider. Without changing anything else, the mobile connection worked, the router received a signal and I was able to connect to the machine via the sim card. This was today at 12:00.
I checked the machine again at 15:00, it was still online. One hour later at 16:00 it is offline again and has been so since.
What could be causing the router to not receive any signal? Our provider has suggested the router might be choosing the wrong operator, resulting in the 0 dB signal. Should the router not automatically select a different operator in this case?
Our provider also suggested to use the auto reboot function of the router to reboot the modem or restart the mobile connection. But if a reboot of the router does not fix the issue, the auto reboot function will not fix this either?
Updating the firmware at this point in time is not really an option, as our manufacturing is geared to work with the 00.01.14.4 firmware. So updating all our systems to a newer firmware involves quite a bit of work and change.
Any suggestions on fixes?