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  • Case ID: 325834
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SLOW REGISTERING ON CELL

babos

Hi,

I have a SIM card that connects via MQTT from an nrf9160 to a server. (using mqtt sample)

The cell search is slow, but once it connects (after a long time), it stays connected until the next reboot. Would it be possible to lock onto the band it connects to, so that it can reconnect immediately upon reboot without having to wait for a long time?


Babos

ncs 2.5.2 sdk 2.3.0 modem 1.3.3

  • 0

    Hi,

    How long time does it take to get connected?

    What system mode (LTE-M and/or NB-IoT) do you have enabled, and what are you connected to?

    In general, the making sure you use the correct system mode, restricting which bands are enabled, manually specifying the PLMN and using the %XCOUNTRDATA AT command can help speed up the network search.

    However, you should be careful when restricting which bands are enabled or which PLMN the modem will search for. If you disable the bands where the networks are deployed, or you limit the search to a PLMN that does not have coverage where the device is, the device will not be able to connect to any networks, even if there are other around.

    The %XCOUNTRYDATA AT command is also a bit limited, as it only modifies how the search is done, but it does not override anything. So if e.g. the SIM card mandates that the device first tries to find a specific network, it does not help (much) that you have said that it should look for another network.

    Once you have connected to a network, you can use the AT+CFUN=0 to store the network parameters to modem flash. This information can then be used in subsequent connections, so that the modem doesn't have to start searching from scratch every time. Note that AT+CFUN=0 will also disconnect you from the network, so while it is very useful during development (use e.g. the at_client, connect to the network, store the parameres to flash, and enjoy the benefits). However, it is a bit less convenient to use for deployed products. Another thing to keep in mind is that if you use it too often, you will eventually wear out the flash in the modem, so it is best not to use it all the time.

    Best regards,

    Didrik

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