nRF9160 Modem NB-IOT network disconnect afterwards the notifications stopped

[optical]

Hello,

we have experienced multiple times during testing that nRF9160 Modem reported CEREG 2. After that it stopped generating any notifications and stopped connecting to the network.

The issue is not easily reproducible, so we cannot provide modem traces.

See AT notification log bellow.
Could you give us a hint, which notification to enable to determine what has happened to the modem ?

What are the cases, which would manifest by disconnecting from the network and not reporting any notification event.

20:07:30.018,000] <inf> dt_modem: Notif: %XSNRSQ: 23,1,172,0
[20:20:40.168,000] <inf> dt_modem: Notif: %CESQ: 39,1,9,1
[20:20:44.370,000] <inf> dt_modem: Notif: %CESQ: 42,2,16,2
[20:20:44.770,000] <inf> dt_modem: Notif: %CESQ: 47,2,21,3
[20:20:45.170,000] <inf> dt_modem: Notif: %CESQ: 46,2,16,2
[20:20:45.570,000] <inf> dt_modem: Notif: %XSNRSQ: 26,2,172,0
[20:20:45.975,000] <inf> dt_modem: Notif: %CESQ: 46,2,21,3
[20:20:47.069,000] <inf> dt_modem: Notif: %XSNRSQ: 29,2,172,0
[20:20:52.504,000] <inf> dt_modem: Notif: %CESQ: 46,2,16,2
[20:20:53.104,000] <inf> dt_modem: Notif: %CESQ: 48,2,21,3
[20:21:04.122,000] <inf> dt_modem: Notif: %CESQ: 44,2,16,2
[20:21:04.922,000] <inf> dt_modem: Notif: %XSNRSQ: 26,2,172,0
[20:21:05.923,000] <inf> dt_modem: Notif: %CESQ: 42,2,11,1
[20:21:07.372,000] <inf> dt_modem: Notif: %XSNRSQ: 23,1,172,0
[20:21:12.173,000] <inf> dt_modem: Notif: %CESQ: 36,1,4,0
[20:21:12.973,000] <inf> dt_modem: Notif: %XSNRSQ: 20,1,172,0
[20:21:21.384,000] <inf> dt_modem: Notif: %XSNRSQ: 17,1,172,0
[20:21:26.334,000] <inf> dt_modem: Notif: %XSNRSQ: 14,0,172,0
[20:21:27.135,000] <inf> dt_modem: Notif: %CESQ: 31,1,0,0
[20:21:28.145,000] <inf> dt_modem: Notif: %CESQ: 38,1,1,0
[20:21:28.536,000] <inf> dt_modem: Notif: %CESQ: 39,1,7,1
[20:21:28.536,000] <inf> dt_modem: Notif: %XSNRSQ: 17,1,172,0
[20:21:30.183,000] <inf> dt_modem: Notif: %XSNRSQ: 20,1,172,0
[20:21:31.004,000] <inf> dt_modem: Notif: %CESQ: 37,1,0,0
[20:21:31.604,000] <inf> dt_modem: Notif: %CESQ: 41,2,7,1
[20:21:34.071,000] <inf> dt_modem: Notif: %CESQ: 43,2,12,1
[20:21:34.071,000] <inf> dt_modem: Notif: %XSNRSQ: 23,1,172,0
[20:21:34.471,000] <inf> dt_modem: Notif: %CESQ: 47,2,17,2
[20:21:35.471,000] <inf> dt_modem: Notif: %XSNRSQ: 26,2,172,0
[20:21:36.071,000] <inf> dt_modem: Notif: %CESQ: 49,2,22,3
[20:21:36.472,000] <inf> dt_modem: Notif: %XSNRSQ: 29,2,172,0
[20:21:37.497,000] <inf> dt_modem: Notif: %XSNRSQ: 32,3,172,0
[20:21:37.897,000] <inf> dt_modem: Notif: %CESQ: 53,2,28,4
[20:21:38.297,000] <inf> dt_modem: Notif: %XSNRSQ: 35,3,172,0
[20:21:39.497,000] <inf> dt_modem: Notif: %CESQ: 48,2,26,3
[20:21:40.544,000] <inf> dt_modem: Notif: %CESQ: 43,2,21,3
[20:21:40.945,000] <inf> dt_modem: Notif: %XSNRSQ: 32,3,172,0
[20:21:48.394,000] <inf> dt_modem: Notif: %XSNRSQ: 29,2,172,0
[20:21:48.415,000] <inf> dt_modem: Notif: %CESQ: 38,1,16,2
[20:21:51.910,000] <inf> dt_modem: Notif: %XSNRSQ: 26,2,172,0
[20:21:53.711,000] <inf> dt_modem: Notif: %CESQ: 41,2,22,3
[20:21:55.536,000] <inf> dt_modem: Notif: %CESQ: 36,1,17,2
[20:21:56.535,000] <inf> dt_modem: Notif: %CESQ: 36,1,12,1
[20:21:57.610,000] <inf> dt_modem: Notif: %CESQ: 39,1,18,2
[20:22:04.130,000] <inf> dt_modem: Notif: %XSNRSQ: 29,2,172,0
[20:22:04.330,000] <inf> dt_modem: Notif: %CESQ: 42,2,23,3
[20:22:06.530,000] <inf> dt_modem: Notif: %CESQ: 38,1,18,2
[20:22:10.372,000] <inf> dt_modem: Notif: %CESQ: 42,2,23,3
[20:22:13.791,000] <inf> dt_modem: Notif: %CESQ: 38,1,18,2
[20:22:14.191,000] <inf> dt_modem: Notif: %CESQ: 37,1,13,1
[20:22:14.991,000] <inf> dt_modem: Notif: %XSNRSQ: 26,2,172,0
[20:22:17.593,000] <inf> dt_modem: Notif: %CESQ: 36,1,8,1
[20:22:18.393,000] <inf> dt_modem: Notif: %XSNRSQ: 23,1,172,0
[20:22:18.993,000] <inf> dt_modem: Notif: %CESQ: 32,1,3,0
[20:22:19.836,000] <inf> dt_modem: Notif: %CESQ: 34,1,9,1
[20:22:22.845,000] <inf> dt_modem: Notif: %CESQ: 34,1,4,0
[20:22:23.671,000] <inf> dt_modem: Notif: %XSNRSQ: 20,1,172,0
[20:22:28.901,000] <inf> dt_modem: Notif: %CESQ: 33,1,9,1
[20:22:29.317,000] <inf> dt_modem: Notif: %CESQ: 31,1,4,0
[20:22:33.823,000] <inf> dt_modem: Notif: %XSNRSQ: 17,1,172,0
[20:22:36.831,000] <inf> dt_modem: Notif: %XSNRSQ: 14,0,172,0
[20:22:37.655,000] <inf> dt_modem: Notif: %XSNRSQ: 11,0,172,0
[20:22:38.535,000] <inf> dt_modem: Notif: +CSCON: 0
[20:22:38.846,000] <inf> dt_modem: Notif: %CESQ: 47,2,20,2
[20:22:38.846,000] <inf> dt_modem: Notif: %XSNRSQ: 29,2,174,0
[20:22:38.846,000] <inf> dt_modem: Notif: +CEREG: 5,"BC48","0006DA21",9,,,"11100000","00101000"
[20:22:38.925,000] <inf> dt_modem: Notif: %CESQ: 49,2,25,3
[20:22:39.086,000] <inf> dt_modem: Notif: +CSCON: 1
[20:22:39.908,000] <inf> dt_modem: Notif: %CESQ: 54,2,28,4
[20:22:39.908,000] <inf> dt_modem: Notif: %XSNRSQ: 32,3,176,0
[20:22:41.497,000] <inf> dt_modem: Notif: %CESQ: 49,2,24,3
[20:22:42.501,000] <inf> dt_modem: Notif: %CESQ: 50,2,19,2
[20:22:42.908,000] <inf> dt_modem: Notif: %CESQ: 56,2,23,3
[20:22:45.501,000] <inf> dt_modem: Notif: %CESQ: 51,2,20,2
[20:22:46.310,000] <inf> dt_modem: Notif: %CESQ: 52,2,25,3
[20:22:47.110,000] <inf> dt_modem: Notif: %CESQ: 49,2,18,2
[20:22:47.711,000] <inf> dt_modem: Notif: %CESQ: 54,2,21,3
[20:22:48.311,000] <inf> dt_modem: Notif: %CESQ: 59,2,25,3
[20:22:49.147,000] <inf> dt_modem: Notif: %CESQ: 53,2,22,3
[20:22:50.111,000] <inf> dt_modem: Notif: %CESQ: 48,2,17,2
[20:22:50.511,000] <inf> dt_modem: Notif: %XSNRSQ: 29,2,176,0
[20:22:53.713,000] <inf> dt_modem: Notif: %XSNRSQ: 26,2,176,0
[20:22:53.913,000] <inf> dt_modem: Notif: %CESQ: 45,2,10,1
[20:22:55.114,000] <inf> dt_modem: Notif: %XSNRSQ: 23,1,176,0
[20:22:55.314,000] <inf> dt_modem: Notif: %CESQ: 41,2,5,0
[20:22:57.518,000] <inf> dt_modem: Notif: %XSNRSQ: 20,1,176,0
[20:22:59.158,000] <inf> dt_modem: Notif: %CESQ: 45,2,10,1
[20:22:59.527,000] <inf> dt_modem: Notif: %CESQ: 49,2,16,2
[20:22:59.927,000] <inf> dt_modem: Notif: %XSNRSQ: 23,1,176,0
[20:23:01.333,000] <inf> dt_modem: Notif: %XSNRSQ: 26,2,176,0
[20:23:05.943,000] <inf> dt_modem: Notif: %XSNRSQ: 29,2,176,0
[20:23:06.165,000] <inf> dt_modem: Notif: %CESQ: 48,2,21,3
[20:23:06.544,000] <inf> dt_modem: Notif: %CESQ: 53,2,24,3
[20:23:06.943,000] <inf> dt_modem: Notif: %XSNRSQ: 32,3,176,0
[20:23:07.744,000] <inf> dt_modem: Notif: %CESQ: 48,2,20,2
[20:23:11.744,000] <inf> dt_modem: Notif: %CESQ: 53,2,23,3
[20:23:12.544,000] <inf> dt_modem: Notif: %XSNRSQ: 35,3,176,0
[20:23:13.959,000] <inf> dt_modem: Notif: %CESQ: 58,2,21,3
[20:23:14.959,000] <inf> dt_modem: Notif: %CESQ: 53,2,19,2
[20:23:18.972,000] <inf> dt_modem: Notif: %CESQ: 48,2,18,2
[20:23:19.172,000] <inf> dt_modem: Notif: %XSNRSQ: 32,3,176,0
[20:23:20.972,000] <inf> dt_modem: Notif: %CESQ: 50,2,23,3
[20:23:22.972,000] <inf> dt_modem: Notif: %CESQ: 55,2,22,3
[20:23:22.972,000] <inf> dt_modem: Notif: %XSNRSQ: 35,3,176,0
[20:23:27.172,000] <inf> dt_modem: Notif: %CESQ: 56,2,27,3
[20:23:28.181,000] <inf> dt_modem: Notif: %CESQ: 52,2,22,3
[20:23:30.583,000] <inf> dt_modem: Notif: %CESQ: 57,2,26,3
[20:23:31.182,000] <inf> dt_modem: Notif: %XSNRSQ: 38,3,176,0
[20:23:32.983,000] <inf> dt_modem: Notif: %CESQ: 52,2,25,3
[20:23:33.589,000] <inf> dt_modem: Notif: %CESQ: 48,2,20,2
[20:23:33.788,000] <inf> dt_modem: Notif: %XSNRSQ: 35,3,176,0
[20:23:34.588,000] <inf> dt_modem: Notif: %XSNRSQ: 32,3,176,0
[20:23:38.389,000] <inf> dt_modem: Notif: %XSNRSQ: 29,2,176,0
[20:23:38.589,000] <inf> dt_modem: Notif: %CESQ: 44,2,15,2
[20:23:41.389,000] <inf> dt_modem: Notif: %CESQ: 47,2,20,2
[20:23:42.589,000] <inf> dt_modem: Notif: %CESQ: 45,2,15,2
[20:23:43.789,000] <inf> dt_modem: Notif: %XSNRSQ: 26,2,176,0
[20:23:44.990,000] <inf> dt_modem: Notif: %CESQ: 45,2,10,1
[20:23:46.191,000] <inf> dt_modem: Notif: %XSNRSQ: 23,1,176,0
[20:23:48.673,000] <inf> dt_modem: Notif: %CESQ: 40,2,5,0
[20:23:49.056,000] <inf> dt_modem: Notif: %XSNRSQ: 20,1,176,0
[20:23:49.456,000] <inf> dt_modem: Notif: %CESQ: 38,1,0,0
[20:23:50.856,000] <inf> dt_modem: Notif: %XSNRSQ: 17,1,176,0
[20:23:52.929,000] <inf> dt_modem: Notif: %XSNRSQ: 14,0,176,0
[20:23:53.224,000] <inf> dt_modem: Notif: +CSCON: 0
[20:23:55.964,000] <inf> dt_modem: Notif: %CESQ: 45,2,10,1
[20:23:55.964,000] <inf> dt_modem: Notif: %XSNRSQ: 28,2,172,0
[20:23:55.964,000] <inf> dt_modem: Notif: +CEREG: 5,"B7FC","0014CD1F",9,,,"11100000","00101000"
[20:23:59.864,000] <inf> dt_modem: Notif: %CESQ: 52,2,8,1
[20:23:59.864,000] <inf> dt_modem: Notif: %XSNRSQ: 23,1,179,0
[20:24:01.987,000] <inf> dt_modem: Notif: +CSCON: 1
[20:24:02.789,000] <inf> dt_modem: Notif: %XSNRSQ: 26,2,179,0
[20:24:03.189,000] <inf> dt_modem: Notif: %CESQ: 57,2,9,1
[20:24:04.189,000] <inf> dt_modem: Notif: %CESQ: 53,2,4,0
[20:24:09.019,000] <inf> dt_modem: Notif: %XSNRSQ: 23,1,179,0
[20:24:09.354,000] <inf> dt_modem: Notif: +CSCON: 0
[20:24:09.627,000] <inf> dt_modem: Notif: %CESQ: 64,3,22,3
[20:24:09.627,000] <inf> dt_modem: Notif: %XSNRSQ: 39,3,191,0
[20:24:09.628,000] <inf> dt_modem: Notif: +CEREG: 5,"BC48","00071020",9,,,"11100000","00101000"
[20:24:10.149,000] <inf> dt_modem: Notif: +CSCON: 1
[20:24:10.150,000] <inf> dt_modem: Notif: %CESQ: 58,2,26,3
[20:24:10.221,000] <inf> dt_modem: Notif: +CSCON: 0
[20:24:10.586,000] <inf> dt_modem: Notif: %CESQ: 255,0,255,0
[20:24:10.586,000] <inf> dt_modem: Notif: %XSNRSQ: 127,0,32767,255
[20:24:10.586,000] <inf> dt_modem: Notif: +CEREG: 2

<---- Device started again and it started working fine.

[09:43:33.201,000] <inf> dt_modem: Notif: %XSIM: 1
[09:43:36.037,000] <inf> dt_modem: Notif: %CESQ: 40,2,20,2
[09:43:36.037,000] <inf> dt_modem: Notif: %XSNRSQ: 31,2,167,0
[09:43:36.038,000] <inf> dt_modem: Notif: +CEREG: 2,"AE38","000D951F",9
[09:43:37.352,000] <inf> dt_modem: Notif: %CESQ: 35,1,19,2
[09:43:39.892,000] <inf> dt_modem: Notif: %CESQ: 30,1,18,2
[09:43:39.893,000] <inf> dt_modem: Notif: %XSNRSQ: 28,2,157,0
[09:43:41.983,000] <inf> dt_modem: Notif: %CESQ: 23,1,0,0
[09:43:41.983,000] <inf> dt_modem: Notif: %XSNRSQ: 23,1,157,0
[09:43:42.650,000] <inf> dt_modem: Notif: +CSCON: 1
[09:43:42.650,000] <inf> dt_modem: Notif: %CESQ: 30,1,11,1
[09:43:43.266,000] <inf> dt_modem: Notif: %CESQ: 31,1,16,2
[09:43:44.650,000] <inf> dt_modem: Notif: %CESQ: 36,1,18,2
[09:43:44.832,000] <inf> dt_modem: Notif: %CESQ: 41,2,22,3
[09:43:45.049,000] <inf> dt_modem: Notif: %XSNRSQ: 26,2,151,0
[09:43:46.035,000] <inf> dt_modem: Notif: %CESQ: 39,1,16,2
[09:43:46.051,000] <inf> dt_modem: Notif: +CGEV: ME PDN ACT 0
[09:43:46.051,000] <inf> dt_modem: Notif: +CEREG: 5,"AE38","000D951F",9,,,"11100000","00101000"
[09:43:46.216,000] <inf> dt_modem: Notif: %XTIME: ,"22805270344480","01"
[09:43:47.443,000] <inf> dt_modem: Notif: %CESQ: 40,2,21,3
[09:43:48.476,000] <inf> dt_modem: Notif: %XSNRSQ: 29,2,151,0
[09:44:18.880,000] <inf> dt_modem: Notif: %XSNRSQ: 32,3,151,0
[09:44:47.708,000] <inf> dt_modem: Notif: %XSNRSQ: 29,2,151,0
[09:44:52.716,000] <inf> dt_modem: Notif: %CESQ: 35,1,13,1
[09:44:53.525,000] <inf> dt_modem: Notif: %XSNRSQ: 26,2,151,0
[09:44:54.908,000] <inf> dt_modem: Notif: %XSNRSQ: 23,1,151,0
[09:44:57.510,000] <inf> dt_modem: Notif: %CESQ: 38,1,18,2
[09:44:58.942,000] <inf> dt_modem: Notif: %XSNRSQ: 26,2,151,0
[09:45:06.566,000] <inf> dt_modem: Notif: %CESQ: 35,1,13,1
[09:45:25.216,000] <inf> dt_modem: Notif: %CESQ: 38,1,18,2
[09:45:29.602,000] <inf> dt_modem: Notif: %CESQ: 35,1,13,1
[09:45:31.391,000] <inf> dt_modem: Notif: %XSNRSQ: 23,1,151,0

[Hakon]

Hello,

is the modem still responsive after the notifications stop? Does the modem respond to at commands?

[optical]

I will have to reproduce the issue to confirm this. This may take some time.

In mean time could you please elaborate on following cases ?

After network disconnect occurs: 
Modem is responding on AT commands.
Modem is not responding on AT commands.

[optical]

The modem is responding to AT commands. In this state.

[Hakon]

stopped connecting to the network.

How do you know that it stopped connecting? Looking at the log, the last thing that happened was that the modem got connected. I can't see any sort of disconnect from the log. Also, if the modem is responding to at commands, what happens on 'at+cereg?'?

[optical]

[20:24:10.586,000] <inf> dt_modem: Notif: +CEREG: 2
Last log before restarting device. 
Doesn't CEREG: 2 Mean:
"2 – Not registered, but UE is currently trying to attach or searching an operator to register to" 

Therefore not connected to the network?