No LTE-M connection when moving from EU to US.

[Moustapha DIENG]

Hello,

I'm working with an nRF9160 using SDK 1.6.1.
I'm using only LTE-M and have set a connection timeout to 75 seconds.

One of my products has left France and arrived in the USA but couldn't establish a connection while another device could.

I have some questions regarding this issue:

1. Is my 75-second timeout sufficient to allow the modem to detect the change in country and perform a scan of the enabled bands
   (all 17 bands supported by the nRF9160 are enabled)?
   The SIM I'm using changes its IMSI when it receives an MCC update from the modem to enable connection in the new country.

2. How long does the modem's scan of the 17 bands take? i.e., B1, B2, B3, B4, B5, B8, B12, B13, B14, B17, B18, B19, B20, B25, B26, B28, and B66.

3. If I reduce the number of enabled bands, how much time can I save on the scan, and is there a formula for this time based on the number of bands enabled?

4. What are the best practices to maximize the chances of connecting in a new country?
   I've seen the %XCOUNTRYDATA command, how can it benefit me?
   
   

Thank you in advance for your assistance.

For your information, I'm using Zephyr via SDK 1.6.1.

[JONATHAN LL]

What modem firmware does the device have?


Also do you have the option to get a modem trace? this will give us insight to what is happening and we will be able to pinpoint what is the problem a lot faster. 

Regards,
Jonathan

[Moustapha DIENG]

Hello, 

We use modem version 1.3.0.

No, I don't have physical access to the product, it's molded in resin.

All I can do is apply an OTA update. That's why I was wondering if you could give me some stats on the time it takes to scan the modem's 17 bands. That way I can adjust my timeout accordingly.

Concerning the traces, is there a way to have them in the logs of my zephyr application without going through the Trace Collector software (as I don't have physical access to the board)?

Best regards.

[Moustapha DIENG]

I forgot to mention that we use sims from 1Global (Truphone) with the reference SIM-S-IO3-MFF2-2-LP.

[JONATHAN LL]

Thanks for the extra details. 

Is my 75-second timeout sufficient

Likely a no, 75 is quite short and for new location\sim the time might be several minutes. 

I've seen the %XCOUNTRYDATA command, how can it benefit me?

It will priorities the bands used in the country so its more likely that it will connect to the band in use in the are it is in sooner. 
Se https://devzone.nordicsemi.com/f/nordic-q-a/105091/nrf9160---lte-m-takes-a-long-time-for-first-connection  for some extra explanation. 
So %XCOUNTRYDATA is a good place to start. 

If I reduce the number of enabled bands, how much time can I save on the scan, and is there a formula for this time based on the number of bands enabled?

Looking in to this

Regards,
Jonathan