Question regarding connection and Fallback

[Giannis Anastasopoulos]

Dear All,

In my application I need to switch on and off the modem using AT+CFUN=0 and AT+CFUN=4 respectivelly.

My question is the following. Let's assume that the device cannot find the preferred type of network and uses the fallback one. Then the modem is switched off. What will happen once the modem is back on again?

Will it try first to connect to the preffered network and then try the fallback, or will it try to connect to the previously working network first?

Thank you very much for your response

[Martin Lesund]

Hi Giannis,

I just got it confirmed internally.

The last registered network is always the highest priority when you turn ON the modem.

Note the word "registered", i.e. we have obtained full service (IP connectivity and so on).

Best regards,
Martin L.

[Giannis Anastasopoulos]

Thank you for your response. I wonder this though:

If you enable the modem and there is no network to connect to, how will the device try the fallback?
To be clear here:

Initially, one can call the lte_lc_init_and_connect(), that will try initially to connect to the preferred network and if that is not available, it will try the fallback. Then one can call the AT+CFUN=4 to go offline. And then one can call AT+CFUN=1.

At this point the modem can either connect to the last network it connected succesfully and this is very clear based on your comments. But what will happen in the case that the previous succesfully-connected-to network is no longer available (e.g. moved to a different region) while in the offline mode? Will the modem execute again the lte_lc_init_and_connect() or something similar?

So basically what I need to know is ho the modem behaves when it cannot find the previously succesfully-connected-to network.

What I know for sure is that if I call the lte_lc_init_and_connect(), every time after CFUN=1 the modem first tries the preferred network and then the fallback, so if I was in an area that only the fallback is available the modem would scan first until the time out for the preferred and then try the fallback.

Thank you very much for your assistance.