nRF9160 stuck in CEREG reject cause 15

[MJD093]

Hi,

I have an issue with the nRF9160 getting stuck in CEREG response 4 (Unknown). When I look into the full CEREG status, I can see that the EMM reject cause is 15 (Cause #15 – No suitable cells in tracking area). This will continue forever as the device seems to have no method of finding a different cell to connect to.

I know that there are cells in my area that I can in fact connect to as a power on reset will find a connectable network in under 30 seconds with a CESQ RSRP of around 20-26. I would like to know is there a method of purging the known cell tower from the modem so that it will not attempt to reconnect with the tower that is sending the rejection? My application swaps between LTE and GPS so the modem characteristics (CFUN, XSYSTEMMODE, MAGPIO, CGDCONT) are being reset between each swap but the previously connected cell is what the device locks onto once LTE is active again.

[2020-02-24 16:59:26] Socket status: 5:11, No more processes
[2020-02-24 16:59:26] Sending AT command: AT+CEREG?
[2020-02-24 16:59:26] Modem response: +CEREG: 1,4
[2020-02-24 16:59:26] OK
[2020-02-24 16:59:26] 
[2020-02-24 16:59:26] Socket status: 18:11, No more processes
[2020-02-24 16:59:26] Failed to receive "+CEREG: 1,5" from modem
[2020-02-24 16:59:26] Requesting Advanced CEREG
[2020-02-24 16:59:26] Radio Scheduler had error with task: 3:-3
[2020-02-24 16:59:27] Sending AT command: AT+CEREG=5
[2020-02-24 16:59:27] Modem response: OK
[2020-02-24 16:59:27] 
[2020-02-24 16:59:27] Socket status: 5:11, No more processes
[2020-02-24 16:59:27] Sending AT command: AT+CEREG?
[2020-02-24 16:59:27] Modem response: +CEREG: 5,4,"A45D","07CBF70B",9,0,15,"11100000","11100000"
[2020-02-24 16:59:27] OK
[2020-02-24 16:59:27] 
[2020-02-24 16:59:27] Socket status: 65:11, No more processes
[2020-02-24 16:59:36] Sending AT command: AT+CEREG=1
[2020-02-24 16:59:36] Modem response: OK
[2020-02-24 16:59:36] 
[2020-02-24 16:59:36] Socket status: 5:11, No more processes
[2020-02-24 16:59:36] Sending AT command: AT+CEREG?
[2020-02-24 16:59:36] Modem response: +CEREG: 1,4
[2020-02-24 16:59:36] OK
[2020-02-24 16:59:36] 
[2020-02-24 16:59:36] Socket status: 18:11, No more processes
[2020-02-24 16:59:36] Failed to receive "+CEREG: 1,5" from modem
[2020-02-24 16:59:36] Requesting Advanced CEREG
[2020-02-24 16:59:36] Radio Scheduler had error with task: 3:-3
[2020-02-24 16:59:37] Sending AT command: AT+CEREG=5
[2020-02-24 16:59:37] Modem response: OK
[2020-02-24 16:59:37] 
[2020-02-24 16:59:37] Socket status: 5:11, No more processes
[2020-02-24 16:59:37] Sending AT command: AT+CEREG?
[2020-02-24 16:59:37] Modem response: +CEREG: 5,4,"A45D","07CBF70B",9,0,15,"11100000","11100000"
[2020-02-24 16:59:37] OK
[2020-02-24 16:59:37] 
[2020-02-24 16:59:37] Socket status: 65:11, No more processes
[2020-02-24 16:59:44] Sending AT command: AT%XVBAT
[2020-02-24 16:59:44] Modem response: %XVBAT: 4395
[2020-02-24 16:59:44] OK
[2020-02-24 16:59:44] 
[2020-02-24 16:59:44] Socket status: 19:11, No more processes
[2020-02-24 16:59:44] iVBatt: 4395
[2020-02-24 16:59:46] Sending AT command: AT+CEREG=1
[2020-02-24 16:59:46] Modem response: OK
[2020-02-24 16:59:46] 
[2020-02-24 16:59:46] Socket status: 5:11, No more processes
[2020-02-24 16:59:46] Sending AT command: AT+CEREG?
[2020-02-24 16:59:46] Modem response: +CEREG: 1,4
[2020-02-24 16:59:46] OK
[2020-02-24 16:59:46] 
[2020-02-24 16:59:46] Socket status: 18:11, No more processes
[2020-02-24 16:59:46] Failed to receive "+CEREG: 1,5" from modem
[2020-02-24 16:59:46] Requesting Advanced CEREG
[2020-02-24 16:59:46] Radio Scheduler had error with task: 3:-3
[2020-02-24 16:59:47] Sending AT command: AT+CEREG=5
[2020-02-24 16:59:47] Modem response: OK
[2020-02-24 16:59:47] 
[2020-02-24 16:59:47] Socket status: 5:11, No more processes
[2020-02-24 16:59:47] Sending AT command: AT+CEREG?
[2020-02-24 16:59:47] Modem response: +CEREG: 5,4,"A45D","07CBF70B",9,0,15,"11100000","11100000"
[2020-02-24 16:59:47] OK
[2020-02-24 16:59:47] 
[2020-02-24 16:59:47] Socket status: 65:11, No more processes
[2020-02-24 16:59:56] Sending AT command: AT+CEREG=1
[2020-02-24 16:59:56] Modem response: OK
[2020-02-24 16:59:56] 
[2020-02-24 16:59:56] Socket status: 5:11, No more processes
[2020-02-24 16:59:56] Sending AT command: AT+CEREG?
[2020-02-24 16:59:56] Modem response: +CEREG: 1,4
[2020-02-24 16:59:56] OK
[2020-02-24 16:59:56] 
[2020-02-24 16:59:56] Socket status: 18:11, No more processes
[2020-02-24 16:59:56] Failed to receive "+CEREG: 1,5" from modem
[2020-02-24 16:59:56] Requesting Advanced CEREG
[2020-02-24 16:59:56] Radio Scheduler had error with task: 3:-3
[2020-02-24 16:59:57] Sending AT command: AT+CEREG=5
[2020-02-24 16:59:57] Modem response: OK
[2020-02-24 16:59:57] 
[2020-02-24 16:59:57] Socket status: 5:11, No more processes
[2020-02-24 16:59:57] Sending AT command: AT+CEREG?
[2020-02-24 16:59:57] Modem response: +CEREG: 5,4,"A45D","07CBF70B",9,0,15,"11100000","11100000"
[2020-02-24 16:59:57] OK
[2020-02-24 16:59:57] 
[2020-02-24 16:59:57] Socket status: 65:11, No more processes
[2020-02-24 17:00:01] Reset variables
[2020-02-24 17:00:01] Changing uControl_Word state
[2020-02-24 17:00:01] IDLE state
[2020-02-24 17:00:01] Event NBIOT_COMPLETE Triggered!
[2020-02-24 17:00:01] Changing uControl_Word state
[2020-02-24 17:00:01] GPS state
[2020-02-24 17:00:01] Sending AT command: AT+CFUN=4
[2020-02-24 17:00:01] Modem response: OK
[2020-02-24 17:00:01] 
[2020-02-24 17:00:01] Socket status: 5:11, No more processes
[2020-02-24 17:00:01] Sending AT command: AT%XSYSTEMMODE=0,0,1,0
[2020-02-24 17:00:01] Modem response: OK
[2020-02-24 17:00:01] 
[2020-02-24 17:00:01] Socket status: 5:11, No more processes
[2020-02-24 17:00:01] Sending AT command: AT%XMAGPIO=1,1,1,1,7,1574,1577
[2020-02-24 17:00:01] Modem response: OK
[2020-02-24 17:00:01] 
[2020-02-24 17:00:01] Socket status: 5:11, No more processes
[2020-02-24 17:00:01] Sending AT command: AT+CFUN=1
[2020-02-24 17:00:01] Modem response: OK
[2020-02-24 17:00:01] 
[2020-02-24 17:00:01] Socket status: 5:11, No more processes
[2020-02-24 17:00:01] Socket created
[2020-02-24 17:00:01] Socket ID 1232491587
[2020-02-24 17:00:01] Fix retry err: 0:11 No more processes
[2020-02-24 17:00:01] Fix interval err: 0:11 No more processes
[2020-02-24 17:00:01] nmea mask err: 0:11 No more processes
[2020-02-24 17:00:01] GPS start err: 0:11 No more processes
[2020-02-24 17:00:01] Changing uControl_Word state
[2020-02-24 17:00:01] GPS state
[2020-02-24 17:00:01] Tracking: 2 Using: 0 Unhealthy: 0
[2020-02-24 17:00:01] Scanning [|]
[2020-02-24 17:00:01] Seconds Since GPS Search Start 0
[2020-02-24 17:00:01] 
[2020-02-24 17:00:02] Tracking: 0 Using: 0 Unhealthy: 0
[2020-02-24 17:00:02] Scanning [/]
[2020-02-24 17:00:02] Seconds Since GPS Search Start 1
[2020-02-24 17:00:02] 
[2020-02-24 17:00:03] Tracking: 0 Using: 0 Unhealthy: 0
[2020-02-24 17:00:03] Scanning [-]
[2020-02-24 17:00:03] Seconds Since GPS Search Start 2
[2020-02-24 17:00:03] 

...................

[2020-02-24 17:01:53] 
[2020-02-24 17:01:54] Tracking: 0 Using: 0 Unhealthy: 0
[2020-02-24 17:01:54] Scanning [|]
[2020-02-24 17:01:54] Seconds Since GPS Search Start 112
[2020-02-24 17:01:54] 
[2020-02-24 17:01:55] Tracking: 0 Using: 0 Unhealthy: 0
[2020-02-24 17:01:55] Scanning [/]
[2020-02-24 17:01:55] Seconds Since GPS Search Start 113
[2020-02-24 17:01:55] 
[2020-02-24 17:01:56] Interrupt tripped!
[2020-02-24 17:01:56] Tracking: 0 Using: 0 Unhealthy: 0
[2020-02-24 17:01:56] Scanning [-]
[2020-02-24 17:01:56] Reading Status Register
[2020-02-24 17:01:56] SPI Interrupt: 0x21
[2020-02-24 17:01:56] Deactivate
[2020-02-24 17:01:56] Disabling UART
[2020-02-24 17:01:56] Disabling SPI
[2020-02-24 17:01:56] Seconds Since GPS Search Start 114
[2020-02-24 17:01:56] 
[2020-02-24 17:01:57] Event DEACTIVATE Triggered!
[2020-02-24 17:01:57] Changing uControl_Word state
[2020-02-24 17:01:57] PRESLEEP state
[2020-02-24 17:01:57] Halting GPS Scan, INT1 shutdown
[2020-02-24 17:01:57] Shutting down GPS
[2020-02-24 17:01:57] Enabling Sleep mode, switching to NB-IoT
[2020-02-24 17:01:57] Sending AT command: AT+CFUN=4
[2020-02-24 17:01:57] Modem response: OK
[2020-02-24 17:01:57] 
[2020-02-24 17:01:57] Socket status: 5:11, No more processes
[2020-02-24 17:01:57] Sending AT command: AT%XSYSTEMMODE=0,1,0,0
[2020-02-24 17:01:57] Modem response: OK
[2020-02-24 17:01:57] 
[2020-02-24 17:01:57] Socket status: 5:11, No more processes
[2020-02-24 17:01:57] Sending AT command: AT%XMAGPIO=1,1,1,1,5,791,849
[2020-02-24 17:01:57] Modem response: OK
[2020-02-24 17:01:57] 
[2020-02-24 17:01:57] Socket status: 5:11, No more processes
[2020-02-24 17:01:57] Sending AT command: AT+CGDCONT=0,"IP","ep.inetd.gdsp"
[2020-02-24 17:01:58] Modem response: OK
[2020-02-24 17:01:58] 
[2020-02-24 17:01:58] Socket status: 5:11, No more processes
[2020-02-24 17:01:58] Sending AT command: AT+CFUN=1
[2020-02-24 17:01:58] Modem response: OK
[2020-02-24 17:01:58] 
[2020-02-24 17:01:58] Socket status: 5:11, No more processes
[2020-02-24 17:01:58] Enabling Sleep mode
[2020-02-24 17:01:58] Changing uControl_Word state
[2020-02-24 17:01:58] IDLE state
[2020-02-24 17:01:59] Sending AT command: AT+CEREG=1
[2020-02-24 17:01:59] Modem response: OK
[2020-02-24 17:01:59] 
[2020-02-24 17:01:59] Socket status: 5:11, No more processes
[2020-02-24 17:01:59] Sending AT command: AT+CEREG?
[2020-02-24 17:01:59] Modem response: +CEREG: 1,4
[2020-02-24 17:01:59] OK
[2020-02-24 17:01:59] 
[2020-02-24 17:01:59] Socket status: 18:11, No more processes
[2020-02-24 17:01:59] Failed to receive "+CEREG: 1,5" from modem
[2020-02-24 17:01:59] Requesting Advanced CEREG
[2020-02-24 17:01:59] Radio Scheduler had error with task: 3:-3
[2020-02-24 17:01:59] Sending AT command: AT+CEREG=5
[2020-02-24 17:01:59] Modem response: OK
[2020-02-24 17:01:59] 
[2020-02-24 17:01:59] Socket status: 5:11, No more processes
[2020-02-24 17:01:59] Sending AT command: AT+CEREG?
[2020-02-24 17:01:59] Modem response: +CEREG: 5,4,"A45D","07CBF70B",9,0,15,"11100000","11100000"
[2020-02-24 17:01:59] OK
[2020-02-24 17:01:59] 
[2020-02-24 17:01:59] Socket status: 65:11, No more processes
[2020-02-24 17:02:09] Sending AT command: AT+CEREG=1
[2020-02-24 17:02:09] Modem response: OK
[2020-02-24 17:02:09] 
[2020-02-24 17:02:09] Socket status: 5:11, No more processes
[2020-02-24 17:02:09] Sending AT command: AT+CEREG?
[2020-02-24 17:02:09] Modem response: +CEREG: 1,4
[2020-02-24 17:02:09] OK
[2020-02-24 17:02:09] 
[2020-02-24 17:02:09] Socket status: 18:11, No more processes
[2020-02-24 17:02:09] Failed to receive "+CEREG: 1,5" from modem
[2020-02-24 17:02:09] Requesting Advanced CEREG
[2020-02-24 17:02:09] Radio Scheduler had error with task: 3:-3
[2020-02-24 17:02:09] Sending AT command: AT+CEREG=5
[2020-02-24 17:02:09] Modem response: OK
[2020-02-24 17:02:09] 
[2020-02-24 17:02:09] Socket status: 5:11, No more processes
[2020-02-24 17:02:09] Sending AT command: AT+CEREG?
[2020-02-24 17:02:09] Modem response: +CEREG: 5,4,"A45D","07CBF70B",9,0,15,"11100000","11100000"
[2020-02-24 17:02:09] OK
[2020-02-24 17:02:09] 
[2020-02-24 17:02:09] Socket status: 65:11, No more processes
[2020-02-24 17:02:19] Sending AT command: AT+CEREG=1
[2020-02-24 17:02:19] Modem response: OK
[2020-02-24 17:02:19] 
[2020-02-24 17:02:19] Socket status: 5:11, No more processes
[2020-02-24 17:02:19] Sending AT command: AT+CEREG?
[2020-02-24 17:02:19] Modem response: +CEREG: 1,4
[2020-02-24 17:02:19] OK
[2020-02-24 17:02:19] 
[2020-02-24 17:02:19] Socket status: 18:11, No more processes
[2020-02-24 17:02:19] Failed to receive "+CEREG: 1,5" from modem
[2020-02-24 17:02:19] Requesting Advanced CEREG
[2020-02-24 17:02:19] Radio Scheduler had error with task: 3:-3
[2020-02-24 17:02:19] Sending AT command: AT+CEREG=5
[2020-02-24 17:02:19] Modem response: OK
[2020-02-24 17:02:19] 
[2020-02-24 17:02:19] Socket status: 5:11, No more processes
[2020-02-24 17:02:19] Sending AT command: AT+CEREG?
[2020-02-24 17:02:19] Modem response: +CEREG: 5,4,"A45D","07CBF70B",9,0,15,"11100000","11100000"
[2020-02-24 17:02:19] OK
[2020-02-24 17:02:19] 

[MJD093]

Hi Martin,

I am not traveling, I am in the same location when I see this issue. I do have bandlocking on band 20 as this is the only known band that Vodafone is operating on in the UK. I could add that command into my application but I would have to wait for the issue to appear again in order to get a read out of that command.

So, are you suggesting that bandlocking should not be done? I have seen this issue on the thingy:91 with magpios set to Band 20 frequencies so I would expect that it shouldn't be able to find anything thing else as it is detuned to other bands.

[Lukáš]

MJD093 said:

I took this same device for a drive as well later in the day. Hours after this log was taken, the device showed visual signs of being unable to reach the network until I had travelled around 5-6 miles. Note, the entire area is within NB-IoT coverage and as mentioned previously, a device reset can yield a very fast network connection even if 5,4 was detected before the reboot.

I think I have approached the same issue as you. Our device is non-stationary and we often receive reject cause 15. Then, the modem is not able to recover until restarted. We use manual COPS to our Vodafone network in the Czech Republic and also band lock for band 20. There are no other bands or NB-IoT providers in our country.

I have described more details in the ticket #243590, but due to some internal details, I had to put it private. While it happens, our CEREG looks following:

[00:30:15.176,330] <dbg> at_cmd.socket_thread_fn: Message: +CEREG: 4,"AE38","0009A120",9,0,15,"11100000","00101000"
[00:30:15.210,815] <dbg> at_cmd.socket_thread_fn: Message: +CEREG: 4,"FFFE","FFFFFFFF",9,0,15,"11100000","00101000"
[00:30:21.024,291] <dbg> at_cmd.socket_thread_fn: Message: +CEREG: 5,"FFFE","FFFFFFFF",9,,,"11100000","00101000"

[Martin Lesund]

Hi mjd093,
If you have bandlocked to the correct bands you should be OK.
Have you concluded what is the sequence to reproduce this issue?

Starting from Power ON reset.

- First device gets service (sometimes or always?)

- Then, the device is stationary, Service just gets lost at some point where it is shown as +CEREG:4 and reject indication?

Do you have a nRF91DK or a Thingy:91 where you can reproduce this issue with modem trace enabled?
Then we could analyze in detail what is going on between the modem and the network.