NB-IOT not connecting on nrf9161 DK

[HoovinSchoovin]

Hi, 

I have been having quite a lot of issues around connectivity and my device, all of which at this point has stemmed from MNO blocking activity from MVNO's (here and here). 

I have LTE-M working when in an areas which supports it, however, i cant ever seem to connect to the NB-IOT networks despite all my efforts. I would very much appreciate walking through the steps i have taken to check if there is anything that i am not thinking of. 

1. After booting up AT_CLIENT, I have ensured that there is a nbiot network in my area: 

> AT+COPS=?
+COPS: (1,"","","21901",9),(1,"","","21910",9)

Am i right in thinking the 9 denotes the network is nbiot?

2. I have ensured my system mode allows for nbiot

> AT%XSYSTEMMODE?
%XSYSTEMMODE: 0,1,1,0

3. I checked the sim im using, and it has nbiot where i currently am situated (Croatia)


4. After no luck, i checked some posts (here) and opted in for legacy PCO instead of ePCO (i did this with CFUN=0 then went to CFUN=1)

> AT%XEPCO=0
OK

After considerable time, the network is still not connected as shown here:

> AT+CEREG?
+CEREG: 0,2

In cellular monitor, the activity status is: "Not registered, attaching or searching". 

Below is my trace file:
trace-2024-09-02T23-02-48.261Z.mtrace

Any help or just suggestions of what to check next would be greatly appreciated. 

SDK Version: v1.6.1
Sim card: Emify (same behaviour on Onomondo too)
Location: Croatia, Dubrovnik (Same has occured in Edinburgh)
Board: NRF9161 DK

Thank you :)

[dejans]

Hi,

You could look at COPS set command. Based on the nRF9160 AT Commands Guide v2.4, COPS set command has 4 parameters which you can choose. For example, you could use it like this for NB-IoT

AT+COPS=1,2,"21901",9

According to documentation, the command configuration is stored in NVM approximately every 48 hours and when the modem is set to minimum functionality mode with the +CFUN=0 command.

Best regards,
Dejan

[HoovinSchoovin]

Hi Dejan,

Thanks for getting back to me. After trying to set the COPS, I got this. I also tried AWS sample and could not get access to internet too. 

> AT+COPS=1,2,"21901",9

OK
> AT+CFUN=0

OK
> AT+CEREG?

+CEREG: 0,4

OK

> AT+CFUN=1

OK
> AT+CEREG?

+CEREG: 0,4

OK
> AT+CEREG?

+CEREG: 0,2,"0CEE","0868235C",9

OK

** AFTER over 10m waiting**

> AT+CEREG?

+CEREG: 0,2,"0CEE","0868235C",9

OK

I've attached the cell monitor screenshot below:


Also, here is the wireshark PDF - note the "DLInformationTransfer-NB, Attach reject (PLMN not allowed)". Could this be the error? :

wireshark_sharkfin-gcjnvzvmst8T4NT2.pcapng.pdf

Any other ideas, please let me know - very much appreciate the help 

[dejans]

Hi,

You can look at AT+CEREG set command (nRF91x1 Cellular AT Commands) and try to set it to value 4 or 5. This should provide more information about the reject cause in your case.
You could also try to set automatic network selection mode (code 0) in the +COPS command.

Best regards,
Dejan

[HoovinSchoovin]

Hi Dejan, 

Thanks for those tips. 

After setting AT+COPS=0, I managed to register to the network .

+CEREG: 5,5,"9D6C","000FA3B6",9,,,"11100000","11100000"

One of the reasons why i had not explored doing that more was this article: here. 

When trying the AWS IOT core, with no changes except for adding in my broker and clientIDs (+certs), I am unable to access the network still. I am guessing this is because the code is not using the AT+COPS=0 command. Any idea how I should proceed. Should I hardcode a COPS=0 in the AWS library somewhere? 

Thanks again for your continued help. 

Kind regards, 
Sam

[dejans]

Hi Sam,

HoovinSchoovin said:

When trying the AWS IOT core, with no changes except for adding in my broker and clientIDs (+certs), I am unable to access the network still. I am guessing this is because the code is not using the AT+COPS=0 command. Any idea how I should proceed. Should I hardcode a COPS=0 in the AWS library somewhere?

Do you have a log which you could share?

Best regards,
Dejan

[HoovinSchoovin]

Hi Dejan, 

Added below:
trace-2024-09-10T19-52-59.542Z.mtrace

[Øyvind]

Hello Sam, Dejan is currently out of office and I have been asked to follow up with your ticket.

Will have a look at the information is this ticket and get back to you within tomorrow. 

Kind regards,
Øyvind

[HoovinSchoovin]

Hello, 
The issue is still persistent across many locations, including Germany. 
Essentially, i can join the network if i force connection using AT+COPS=0 while in AT client. 
The modem wont automatically connect on my aws iot application. It is stuck at +CEREG: 2,"C938","01870701",7. 

[Øyvind]

Hello, 

Looking at the modem trace provided, your device enters a reset loop. You must ensure that you do not reset your device too many times without properly disconnecting your device from the network.

The activation of the reset loop restriction starts the timer with a 30 minute period. During this time, the modem blocks all Attach attempts. After the timer has expired, the modem starts normal behavior and automatically regains LTE service for possible connections the same way as when the modem is activated without the reset loop restriction.

Kind regards,
Øyvind

[HoovinSchoovin]

Hi Øyvind, 

Thanks for getting back to me. 

I've tried to get another trace, but no matter how much i try (changing the ports for trace serial and terminal etc) a red cross comes up next to trace on the connection status. 

I get these issues

16:16:55.793

AT command AT+CPIN? failed: +CME ERROR

16:16:55.798

AT command AT+CIMI failed: : 13 +CME ERROR

16:16:55.958

AT command AT%XICCID failed: +CME ERROR:


I imagine i'm doing something wrong, but all tutorials are quite old. Are there any up to date docs or do you have any idea what might be the issue?

Thanks in advance. 

[Øyvind]

HoovinSchoovin said:

I imagine i'm doing something wrong, but all tutorials are quite old. Are there any up to date docs or do you have any idea what might be the issue?

Thanks in advance. 

What tutorials are you referring to? 

HoovinSchoovin said:

I get these issues

From my initial look these are related to an issue with your UICC/SIM card. Are you able to provide full application logs instead. Please "refresh dashboard" in Cellular Monitor.

As this is a DK, there should not be an issue with collecting modem traces with this guide.