nRF9160 don't see the NB-IoT networks

[Vladimir Aparin]

I alredy run the assert tracking about 4 months ago on preliminary firmware.

Now I updated the modem firmware to v1.0.0 and compiled the last stable AT Client project from repositary.

Now I can't see any networks at all (AT+COPS=? shown nothing) and as resul i can connect and register anywhere.
At the same time the network is present and the SIM is working - uBlox SARA-R410 on the same table working fine.

I tried some samples from the repositary and got the same result - the nRF9160 can't connect to the network!

What's may going wrong? How to fix it.

[MJD093]

If you updated the modem's firmware recently to the latest version, you must specify what LTE specification you wish to use. Have you remembered to use the AT%XSYSTEMMODE command to set the Modem to NB-IoT mode?

Please describe how you are using the AT Client to access the NB-IoT network. Also provide some UART logs of the at_client commands and responses your device is outputting.

[Vladimir Aparin]

***** Booting Zephyr OS v1.14.99-ncs2 *****

The AT host sample started

AT%XSYSTEMMODE=0,1,0,0
OK

AT+CFUN=1
OK

AT+CEREG=2
OK

AT+COPS=?

[MJD093]

How long after setting CFUN=1 are you calling COPS=?

At+CEREG? is a better debug command for network attachment as it provides information on eNodeB attachment and the current state of the modem in the attachment process. Could you provide the response of that command?

[Vladimir Aparin]

In 5 seconds approximatelly.

See the log about

***** Booting Zephyr OS v1.14.99-ncs2 *****

The AT host sample started

AT+CFUN=1
OK

AT+CEREG?
+CEREG: 0,4,"FFFE","FFFFFFFF",7

OK

AT+CEREG=2
OK

AT+COPS=?
AT+CEREG?

[Vladimir Aparin]

I see that it's required to read CFUN status and got 1 before works onward.

I configured the bands (B3, B8, B20) but I still see the 0 (unknown) in answer.

***** Booting Zephyr OS v1.14.99-ncs2 *****

The AT host sample started

AT%XCBAND
%XCBAND: 0

OK

AT%XCBAND=?
%XCBAND: (1,2,3,4,5,8,12,13,14,17,18,19,20,25,26,28,66)

OK

AT%XBANDLOCK=1,"10000000000010000100"
OK

AT%XCBAND
%XCBAND: 0

OK


AT%XCBAND=?
%XCBAND: (3,8,20)

OK

AT+CFUN?
+CFUN: 4

OK

AT+CFUN=1
OK

AT+CFUN?
+CFUN: 1

OK

AT+COPS?
+COPS: 0

OK

AT+COPS?
ERROR

AT+COPS?
+COPS: 0

OK

AT+CEREG=2
OK

AT+COPS?
+COPS: 0

OK

AT+CEREG?
+CEREG: 2,2,"FFFE","FFFFFFFF",7

OK

AT+CEREG?
+CEREG: 2,2,"FFFE","FFFFFFFF",7

OK

[MJD093]

Ok, attachment to a network isn't likely happen that quickly. I have seen the attachment take several minutes in poor reception areas. You need to give the module at least a minute before testing if it has made a connection. It is not necessary to read the status of CFUN, CFUN must be set to 1 in order for the modem to activate but you do not need to read the status of CFUN for the modem to attach. I wouldn't worry too much about band selection, this should be automatic as the device will default to scanning all LTE bands.

An additioanl question, are you testing this inside a building or in the open air, away from structures? From my own personal testing with the pca10090 DK, the reception will be quite low inside a structure, usually lower than -110dBm