NRF9160 not connecting ESM/EMM errors

[9160-DEV]

Hello,

I have an NRF9160DK board and a custom board running the SLM application that are exhibiting similar behaviour.  Both boards work fine with the supplied iBasis SIM.  When I use some purchased SIMs from the operator Vodafone I cannot get past "searching" (CEREG: 2) - I've left it a couple of hours and no success.  The Vodafone SIMS worked when I last tried them a couple of months ago, the signal strength is currently good (-90dBm) and Vodafone report no issues on their NB-IoT network according to their coverage map.

The notification output from the SLM contains:

+CNEC_ESM: 29,0                         User authentication failed

+CNEC_EMM: 19                            ESM Failure

I have contacted my supplier who have asked to check the APN settings.  I don't think it is getting far enough through the network connection process for this to take affect though.  Isn't APN after network connection?

Does anyone have any advice or experience that may assist me resolving this via the suppliers support?

Thank you.

[Achim Kraus]

According your trace

+CEREG: 2,"2421","07D4E21F",9,0,19  

the modem connects to base station 513250 using NB-IoT and gets rejected.

Cellmapper.net shows that Vodafone (PLMN 23415) base station in Gillingham.

For the other +CEREG cellmapper doesn't know the base stations.

Maybe that helps.

[9160-DEV]

Thank you for looking at the trace.

I don't know if I'm reading it 100% correctly, but the EMM reject causes appear to change depending on the towers shown by +CEREG, eg EMM 15, 26, 29.  See below. 

+CEREG: 2,"2421","07C18A1F",9
+CNEC_ESM: 29,0
+CNEC_EMM: 19

+CEREG: 2,"2421","07C18A1F",9,0,19
+CNEC_EMM: 15

+CEREG: 2,"B951","00363015",9,0,15
+CNEC_EMM: 15

+CEREG: 2,"0390","07CA806E",7,0,15

+CEREG: 2,"241F","07B68F15",9
+CNEC_ESM: 26,0
+CNEC_EMM: 19

+CEREG: 2,"2421","07C18A1F",9
+CNEC_ESM: 29,0
+CNEC_EMM: 19

In the same trace I have "No Suitable Cells"(15) and "ESM Failure"(19), plus "User Authentication Failed"(29) and "Insufficient Resources" (26).

Is the user authentication error likely to be a low level SIM issue rather than AT+CGAUTH mistake?

Vodafone shows "Good" NB-IoT coverage using their coverage mapper tools online, and no tower issues in the area (even if there were, it seems to be changing between towers so would have thought that wouldn't be an issue?

The output of AT+COPS=? is

+COPS: (1,"","","23415",9),(1,"","","23430",9)

The first is Vodafone and the second one EE.  When I ran it again I've also seen a third operator O2.

[9160-DEV]

Thank you for this resource.  The base stations it finds when I have run it again are all surprisingly far away (5-6 miles) minimum.

[Achim Kraus]

You're welcome.

"surprisingly far away (5-6 miles) minimum."

on the countryside that should still work. Otherwise you may try out testing closer to the towers ;-).

[9160-DEV]

No change unfortunately, just better RSRP/RSRQ.

Do all towers support NB-IoT for a given provider, or is it the case that the NRF9160 polls each tower it finds until one appears that supports it?  I've driven to four local 'big' towers and the same result at each.