LTE connection drops after two minutes


I am currently working with an APU2C4 and I am trying to connect to an LTE network using the Telit LM940. I communicate with LM940 using uqmi commands and I am able to connect to the network but the connection usually drops after two minutes.

As AT commands are not at my disposal in the APU, I connected the modem to my computer, which is running Windows, in order to check what was going on. To my surprise, no new networks were shown in my taskbar when I connected the modem. Fortunately, this problem is solved by disconnecting, waiting some minutes and connecting again and when the modem is working the connection never drops on Windows.

When the modem is not working on Windows, I obtain the following output:

+CREG?: 0,2

+COPS?: 0

+CGATT?: 0

And when the modem works on Windows, I obtain this other:

+CREG?: 0,1

+COPS?: 0,0,””,7

+CGATT?: 1

The weird thing is that if I connect the modem back to the APU after it has run successfully on Windows, the connection is stable for more than two minutes, approximately 15, but afterwards it disconnects.

I have checked the APN hundreds of times and everything seems to be correct.

Could you give an idea why the Telit LM940 doesn’t work in the APU?

Thanks in advanced!