Are application-level back-offs required for modem registration?

[RonanB96]

NCS 1.8.0

Modem FW 1.3.1

For other products I've worked on with cellular modems, we would add in back-offs to the firmware in the case we failed to open a PPP session after registration. This was to pass the FCC and RED certifications.

For the nRF91 we aren't calling any equivalent function to open a PPP connection, just opening sockets when we are registered.

So my question is, do we need to add any application-level backoffs or does the underlying library/modem handle this?

Our modem handling code is very close to the modem_module.c from the asset tracker v2 and using  lte_lc_connect_async without any PSM or eDRX modes enabled.

Somewhat related question, I have left the board attempting to register for long periods of time (1h+) without registering to a network but after pressing reset the board registered straight away, should we add in a modem reset after some timeout without registering to the network?

Our application is mains powered so power isn't a concern.

[JONATHAN LL]

Update:
lte_lc_connect_async() basically just sets the modem to normal mode. In this mode, modem tries to stay registered to the network and no actions from the application should be required. Depending on why modem wasn't able to register to the network in the first place, there may be a delay before modem attempts registration again. For example, if attach is rejected by the network, there may be a specific time the device needs to wait before it's allowed to attempt again.

Regards,
Jonathan

[RonanB96]

Hey Jonathan,

Regarding this:

"there may be a specific time the device needs to wait before it's allowed to attempt again."

I'm assuming this is something the modem handles internally and requires no application logic changes?

Thanks

Ronan

[JONATHAN LL]

Yes that is correct

Regards,
Jonathan