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  • Case ID: 236974
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How long should nRF9160 stay in CEREG mode 4 on startup?

Jonathan

When I start my nRF9160 modem (AT+CFUN=1) it can sit in CEREG mode 4 (unknown) for a couple of minutes, before it switches to 2 (searching) then 1 (registered).

Is that normal? Is there any way to speed it up?

It is running modem firmware 1.0.1.

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    One thing we stumbled on was that our application was re-forcing a bunch of modem settings on every power up, but some of them would cause the modem to lose warm-start info it had saved previously.  Specifically, we found that sending "AT+COPS=0" on every power-up before going online would trigger a full sweep and auto-select which could take minutes.  If we skipped that, the modem would retain warm-start info under some conditions (not entirely clear to me when) and would often be able to get online in less than 5 seconds.

    If we query the COPS setting it still shows 0 and the modem will still jump between operators if it loses connection, but it can remember who it connected to previously and re-use that as a first attempt on the next power cycle.  The first connect in a new location will still take minutes, but for our product that is less likely to happen.

    As a matter of curiosity, can anyone from Nordic comment on when the modem will save information like this for use after reboot?  Our application doesn't normally go to CFUN=0, so I'm pretty sure that's not triggering it. Yet, our devices connect very quickly and appear to have saved sometime.

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    One thing we stumbled on was that our application was re-forcing a bunch of modem settings on every power up, but some of them would cause the modem to lose warm-start info it had saved previously.  Specifically, we found that sending "AT+COPS=0" on every power-up before going online would trigger a full sweep and auto-select which could take minutes.  If we skipped that, the modem would retain warm-start info under some conditions (not entirely clear to me when) and would often be able to get online in less than 5 seconds.

    If we query the COPS setting it still shows 0 and the modem will still jump between operators if it loses connection, but it can remember who it connected to previously and re-use that as a first attempt on the next power cycle.  The first connect in a new location will still take minutes, but for our product that is less likely to happen.

    As a matter of curiosity, can anyone from Nordic comment on when the modem will save information like this for use after reboot?  Our application doesn't normally go to CFUN=0, so I'm pretty sure that's not triggering it. Yet, our devices connect very quickly and appear to have saved sometime.

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