nRF9151: Network scanning behaviour

[klaasg]

Hi.

We are doing automatic network attaching on nRF9151. This is how the flow looks:

1. AT%XBANDLOCK=2,...
2. AT+CFUN=1
3. AT+COPS=0

We do this until we get registered or we get %MDMEV: SEARCH STATUS 2. According to the documentation, this means that the network search is completed.

But for some configurations, like only using one band, this is suspiciously fast. Example: around 7 seconds for band 20.

Are we always sure that all PLMNs and all frequencies are scanned? Or does the modem do optimisations, like the ones described in the documentation of AT%PERIODICSEARCHCONF or AT%XDATAPRFL. We don't currently use these commands because we're always triggering searches and not doing anything periodically.

Thank you!

[Øyvind]

Hello,

But for some configurations, like only using one band, this is suspiciously fast. Example: around 7 seconds for band 20.

Are you doing this every time your device powered on? Suspiciously fast in what way? Do you have a band lock on band 20 alone?

Are we always sure that all PLMNs and all frequencies are scanned?

All frequencies, yes. PLMN are not included in scan. Note that the modem handles search / scan as per 3GPP. It will store data in memory when suitable networks are found. 

We don't currently use these commands because we're always triggering searches and not doing anything periodically.

What exactly are you trying to achieve?

Kind regards,
Øyvind