PSM in SLM application using nRF9160-DK

[AndMar8]

Hi,

I'm using the SLM application and I would like to test the PSM on the nRF9160-DK but its timers seems to be aperiodic (instead of periodic).

I set it using the at command: AT+CPSMS=1,"","","10101010","00100001"

It should means:

Timer T3412 (TAU) every 10 minutes and timer T3324 which lasts 1 minute

But analyzing the +CSCON: 1, +CSCON: 0 and +CEREG:... it seems to not be periodic.

I test it for some hours and after the +CSCON: 0 the +CSCON: 1 appers always in different moment. In the following I have written the time I had to wait for the +CSCON: 1:

+CSCON: 0 --> 54 minutes --> +CSCON: 1

+CSCON: 0 --> 25 minutes --> +CSCON: 1

+CSCON: 0 --> 48 minutes --> +CSCON: 1

+CSCON: 0 --> 19 minutes --> +CSCON: 1

I expect instead:

+CSCON: 0 --> 10 minutes --> +CSCON: 1

+CSCON: 0 --> 10 minutes --> +CSCON: 1

+CSCON: 0 --> 10 minutes --> +CSCON: 1

+CSCON: 0 --> 10 minutes --> +CSCON: 1

The following lines are what I see on Termite:

AT+CEREG=5
OK
AT+CSCON=1
OK
AT+CPSMS=1,"","","10101010","00100001"
OK
AT+CFUN=1
OK
+CEREG: 2,"9129","0AAE9CA1",9,0,0,"11100000","11100000"
+CSCON: 1
+CEREG: 1,"9129","0AAE9CA1",9,,,"00011110","11100000"
+CSCON: 0
AT+CPSMS?
+CPSMS: 1,,,"10101010","00100001"
OK

1) I noticed that the timers setted with AT+CPSMS ("10101010","00100001") are different from the timers shown with +CEREG ("00011110","11100000"), should be a problem?
2) I try also setting the same timers on SEGGER in "Configure nRF Connect SDK project" with LTE_PSM_REQ_RPTAU and LTE_PSM_REQ_RAT, but I obtain the same result, any suggestions?

I'm in italy and I'm using a TIM sim card.

Thanks in advance

[Heidi]

Hi!

Firstly, note that the values you set in +CPSMS are just requests and the network can set a different value. As for the +CEREG returns, this is what they mean:

+CEREG: <stat>[,[<tac>],[<ci>],[<AcT>][,<cause_type>],[<reject_cause>][,[<Active-Time>],[<Periodic-TAU>]]]]

+CEREG: 2,"9129","0AAE9CA1",9,0,0,"11100000","11100000"
<Active-Time>: 11100000 - timer deactivated
<Periodic-TAU>: 11100000 - timer deactivated

+CEREG: 1,"9129","0AAE9CA1",9,,,"00011110","11100000"
<Active-Time>: 00011110 - 1 minute (bin11110 is dec30 x 2 seconds)
<Periodic-TAU>: 11100000 - timer deactivated

Please wait for connection status 5 - Registered roaming and see what timer values are returned then, to check what values the network set.

Also please note that there are both periodic TAU (T3412) and extended periodic TAU (T3412ext), and +CEREG will only give you the extended periodic TAU value. To see the periodic TAU value that the network has set, you have to use %XMONITOR (and mfw >=1.2.0). 

But it's still strange that the intervals vary as much as they do. Are you able to capture a modem trace? Perhaps the network is changing the period, or the UE could have connected to a different network with different parameters during your testing.

Let me know!

Best regards,

Heidi

[AndMar8]

Hi!

Thanks for the reply.

Heidi said:

Please wait for connection status 5 - Registered roaming and see what timer values are returned then, to check what values the network set.

I'm not sure that this could happen. I have a TIM sim and I'm in Italy so the connection status could be only +CEREG: 1 (Registered, home network). At least I think so.
I had the connection status 5 with the IBASIS sim but now I can't use it for some reasons.
Is it important to have the connection status +CEREG: 5 for the PSM timers?

Heidi said:

you have to use %XMONITOR (and mfw >=1.2.0)

Thanks I will check this command!

Heidi said:

Are you able to capture a modem trace?

Yes I'm able but not in this moment, I have to wait the next week. Cause the jlink of my DK is broken and I need an external jlink to program it. 

I will let you know for the modem trace.
Thanks again for the help.

best regards

[AndMar8]

Quick update...

I tried the %XMONITOR:

Ready
AT+CSCON=1

OK
AT+CEREG=5

OK
AT+CPSMS=1,"","","10101010","00100001"

OK
AT+CFUN=1

OK

+CEREG: 2,"9287","0AB352A2",9,0,0,"11100000","11100000"

+CSCON: 1

+CEREG: 1,"9287","0AB352A2",9,,,"00011110","11100000"
AT%XMONITOR

%XMONITOR: 1,"","","22201","9287",9,20,"0AB352A2",458,6290,42,27,"","00011110","11100000"

OK

The active time "00011110" in +CEREG:1 and %XMONITOR is the one that I had set directly from SEGGER (LTE_PSM_REQ_RAT). It seems that I can't change the value of the timer via AT command.

best regards

[Heidi]

Hi, from the return of %XMONITOR, it doesn't look like you are using MFW v.1.2.0 or higher.

The periodic TAU returned from %XMONITOR with MFW < 1.2.0 is the extended timer value. If possible, update the MFW and run the command again.

AndMar8 said:

The active time "00011110" in +CEREG:1 and %XMONITOR is the one that I had set directly from SEGGER (LTE_PSM_REQ_RAT). It seems that I can't change the value of the timer via AT command.

 

You requested the active time "00100001" which is bin(00001) = dec(1) and 001 means the value is incremented in the multiples of one minute, so you requested one minute. 

The active time that's been set by the network is "00011110" which is bin(11110) = dec(30) and 000 means the value is incremented in the multiples of two seconds, so they also set one minute. It's just a different way of writing it. 

You are able the request a different timer value via AT command, but again, the network can set a different value from what is requested. 

I will need a modem trace to figure out why the time periods between idle and connected mode are aperiodic. 

Best regards,

Heidi

[AndMar8]

Hi,

I update the modem firmware to version 1.2.3 and this is what I obtain:

Ready
[00:00:00.217,681] [1B][0m<inf> app: Serial LTE Modem[1B][0m
AT+CEREG=5
OK
AT+CSCON=1
OK
AT+CPSMS=1,"","","10101010","00100001"
OK
AT+CFUN=1
OK
+CEREG: 2,"9129","0AAE9CA1",9,0,0,"11100000","11100000"
+CSCON: 1
+CEREG: 1,"9129","0AAE9CA1",9,,,"00011110","11100000"
+CSCON: 0
AT%XMONITOR
%XMONITOR: 1,"","","22201","9129",9,20,"0AAE9CA1",437,6290,15,19,"","00011110","11100000","01001001"
OK

I see that the periodic-tau set with +CPSMS ("10101010") is different from the one obtained with %XMONITOR ("01001001").

I attached the bin file obtained with the modem trace.
What can I do to set correctly the TAU timer for the PSM?
7140.trace-2021-04-14T12-26-03.838Z.bin

[Heidi]

Hi!

I'm not able to download the modem trace you attached. I just see Page Not Found.

Even though you are requesting a Periodic TAU of 10 minutes, the network is free to assign another value, so that might be what is happening. 

Best regards,

Heidi