NRF9160 modem: How to search NB network?

I am testing the power consumption of our products and found a problem here: when the external signal is not good, the Modem will search the NB-IoT network signal at regular intervals automatically!(about once every 2 minutes, lasting for 1 minute and 20 seconds each time)  But my application didn't set this action, and I did get a connection timeout message in the NCS w_lte_LC_connect function, so who was controlling the modem to keep searching the web at regular times?

my ncs version is 1.2.0

  • Hi,

     

    The lte_lc library, which is in use in your application, has a default timeout per the configuration "CONFIG_LTE_NETWORK_TIMEOUT".

    If the config "CONFIG_LTE_NETWORK_USE_FALLBACK" is enabled, it will then try on the other mode (ie: if searching NB1, it switches to M1).

     

    If you want the modem to search for a longer period, you can adjust the above timeout configuration.

     

    Kind regards,

    Håkon

  • Yes, i had set CONFIG_LTE_NETWORK_USE_FALLBACK=n and CONFIG_LTE_NETWORK_TIMEOUT=60. As described in my picture, the program had timed out after one minute of searching, and did not switch to another mode to continue searching. I do not know why the modem atimed the search action utomatically.

  • Hi,

     

    duxinglang said:
    CONFIG_LTE_NETWORK_USE_FALLBACK=n and CONFIG_LTE_NETWORK_TIMEOUT=60.

    This means that it will search for up to 60 seconds, then turn off the modem, as per the behavior in lte_lc.c.

     

    duxinglang said:
    As described in my picture, the program had timed out after one minute of searching, and did not switch to another mode to continue searching. I do not know why the modem atimed the search action utomatically.

     What are you trying to obtain? If you want it to search for a longer period, just adjust the CONFIG_LTE_NETWORK_TIMEOUT parameter.

     

    Kind regards,

    Håkon

  • I mean, why is it that when the modem doesn't find a signal within the time I set it to, it automatically goes back to searching for a signal instead of just stopping?After all, I didn't set it up to periodically search for signals

  • Hi,

     

    duxinglang said:
    I mean, why is it that when the modem doesn't find a signal within the time I set it to, it automatically goes back to searching for a signal instead of just stopping?After all, I didn't set it up to periodically search for signals

    I am sorry, my former behavior description is not correct. 

    If it times out, and  CONFIG_LTE_NETWORK_USE_FALLBACK=n, the lte_lc library will not change the modem mode (in AT+CFUN), and rather let the application handle this specific scenario. It will still be in searching mode unless the application turns the modem off or places it in airplane mode.

     

    Kind regards,

    Håkon

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