PSM TAU not triggering after set time

[MJD093]

Hi,

I am trying to test PSM settings on the nRF9160 using a custom PCB. I have set the active time to 3 minutes with a periodic TAU time of 10 minutes.

When the device enables PSM, I see the following response:

Activating PSM Mode
Opening AT Command Socket
Socket ID: 1
Sending AT command: AT+CPSMS=1,,,"10101010","10100011"
Modem response: OK

Socket status: 5:11, No more processes
Sending AT command: AT+CPSMS?
Modem response: +CPSMS: 1,,,"10101010","10100011"
OK

Socket status: 40:11, No more processes

I set the PSM timers and then read them back to check if they have been set. Both the set and read AT commands are the same values so the device should be operating under these timers but after 20 minutes I have yet to see the modem reactivate.

Am I missing something? (I would post an image of the current consumption but the forum isn't letting me do that at this time)

MJD093

[MJD093]

I did a little digging and can see what the issue is now. CEREG lvl 5 shows the network accepted response and it's being forced up to 3 hours active and 70 minutes TAU.

What effect does this have on the module?

*** Booting Zephyr OS build v2.1.99-ncs1-3-g7ddab664b04b  ***
The AT host sample started
AT+CFUN?
AT+COPS?
AT+CFUN?
+CFUN: 0
OK
AT
OK
AT+CFUN?
+CFUN: 0
OK
AT%XBANDLOCK=1,"10000000000000000000"
OK
AT+CGDCONT=0,"IP","ep.inetd.gdsp"
OK
AT%XSYSTEMMODE= 0,1,0,0
OK
AT+CFUN=1
OK
AT+CEREG?
+CEREG: 0,4,"FFFE","FFFFFFFF",9
OK
AT+CEREG?
+CEREG: 0,4,"FFFE","FFFFFFFF",9
OK
AT+CEREG?
+CEREG: 0,5,"A44F","07BF3315",9
OK
AT+COPS=3,2
OK
AT+COPS?
+COPS: 0,2,"23415",9
OK
AT%XCBAND
%XCBAND: 20
OK
AT+CGDCONT?
+CGDCONT: 0,"IP","ep.inetd.gdsp","10.21.124.101",0,0
OK
AT+CGACT?
+CGACT: 0,1
OK
AT+CESQ
+CESQ: 99,99,255,255,21,41
OK
AT+CESQ
+CESQ: 99,99,255,255,21,41
OK
AT+CPSMS?
+CPSMS: 0
OK
AT+CPSMS=1,,,"10101010","10100011"
OK
AT+CPSMS?
+CPSMS: 1,,,"10101010","10100011"
OK
AT+CPSMS?
+CPSMS: 1,,,"10101010","10100011"
OK
AT+CPSMS?
+CPSMS: 1,,,"10101010","10100011"
OK
AT+CPSMS?
+CPSMS: 1,,,"10101010","10100011"
OK
AT+CEREG?
+CEREG: 0,5,"A44F","07BF3315",9
OK
AT+COPS=3,2
OK
AT+COPS?
+COPS: 0,2,"23415",9
OK
AT%XCBAND
%XCBAND: 20
OK
AT+CGDCONT?
+CGDCONT: 0,"IP","ep.inetd.gdsp","10.21.124.101",0,0
OK
AT+CGACT?
+CGACT: 0,1
OK
AT+CEREG=5
OK
AT+CEREG?
+CEREG: 5,5,"A44F","07BF3315",9,,,"00100011","00000111"
OK
AT+COPS=3,2
OK
AT+COPS?
+COPS: 0,2,"23415",9
OK
AT%XCBAND
%XCBAND: 20
OK
AT+CGDCONT?
+CGDCONT: 0,"IP","ep.inetd.gdsp","10.21.124.101",0,0
OK
AT+CGACT?
+CGACT: 0,1
OK

[Didrik Rokhaug]

Hi.

I think you have gotten your bits turned around.

AT+CPSMS=1,,,"10101010","10100011"

Here you request a periodic TAU of 10 minutes (as you state in the original question), but the requested active time is not valid.

"101" is not a valid timer value unit for the active time. Instead, it is interpreted as 1 minute as specified by 3GPP.

 

MJD093 said:

CEREG lvl 5 shows the network accepted response and it's being forced up to 3 hours active and 70 minutes TAU.

 It shows an active time of 3 minutes (001 - value is incremented in multiples of 1 minute), and 70 minutes TAU.

The values for the units of active time and periodic TAU is different.

 

MJD093 said:

What effect does this have on the module?

 I am not entirely sure I understand what you are asking here, but I'll give it a go:

When you enter PSM, the device will be unreachable from the network for 70 minutes or until it transmits, whichever is shortest.

After the device has reconnected to the network (either to send data or for a periodic TAU) it will stay connected for 3 minutes before it again will enter PSM.

Best  regards,

Didrik

[MJD093]

Didrik Rokhaug said:

 I am not entirely sure I understand what you are asking here, but I'll give it a go:

This was in relation to the fact I believed I was seeing conflicting results for the PSM timers on the current consumption. I was seeing 3 minutes active modem drain followed by an offline modem drain when I was expecting a longer active time based on my understanding of the timer bits at that moment.

Didrik Rokhaug said:

I think you have gotten your bits turned around.

Yes it would appear so, I was unaware that the Active Time value used a different encoding to the TAU timer. Thank you for clarifying this error. I can now see that Active Time uses encoding from GPRS Timer 1 whereas the TAU timer uses GPRS Timer 3 encoding, both using different encoding for bits 8, 7, 6.

Thank you for your help in understanding what has gone wrong here.