How to achieve NB-IoT/LTE-M fallback in NRF9160 ?

[Manu_Devappa]

I'm Using sim card which support both LTE and NB-IoT. In some areas i can't use LTE-M and in that case i need to switch it to NB-IoT. I referred and there is fallback method which can do this. I want to know how to do that in code. Can somebody help me to figure it out please. I'm new to this game. 

[Håkon Alseth]

Hi,

 

The "lte_lc" module has a option for a fallback, but this is only on the initial connect to the network.

In order to change the network mode dynamically, this should be implemented in your application.

You could do something like this:

1. check the network state for x amount of time (For instance AT+CEREG?)

2. If state is not connected (see here: https://infocenter.nordicsemi.com/topic/ref_at_commands/REF/at_commands/nw_service/cereg_read.html?cp=2_1_7_6_1)

you can change to flight mode (AT+CFUN=4)

3. Change the systemmode (AT%XSYSTEMMODE) to your preferred mode

4. go back to online mode (AT+CFUN=1) and see if it connects on the newly selected network mode

  

Note: you can use modem_info to get some of the above mentioned notifications (from AT+CEREG) if wanted.

 

Kind regards,

Håkon