Does the modem turn on some functions periodically?

[duxinglang]

I am testing the power consumption of my client board, turning off all external functions and only remaining connected to the NB network.  During the test, about every 30 minutes, there is a brief and large increase in power consumption. Is the Modem performing network related operations?  During initialization, I have set the modem to PSM mode with the following parameters:  

# PSM
CONFIG_LTE_PSM_ENABLE=y
# Set Periodic-TAU timer to 10 minutes and Active-Time to 20 seconds.
CONFIG_LTE_PSM_REQ_RPTAU="10101010"
CONFIG_LTE_PSM_REQ_RAT="00001010"

It seems that the Modem does not follow this set interval for network operations. Why?  

[Didrik Rokhaug]

Hi,

It is hard to say anythig with certainty without seeing some logs or power profiling, but here is what I believe is what happens:

When in PSM, the modem will sleep until either the application sends some data, or it is time for the next Periodic Tracking Area Update (TAU).

These TAUs are necessary for the device to stay connected to the network, and to see if there is any incoming data.

While the device can request a specific Periodic TAU interval and Active Time, it is up to the network to decide if the device is granted PSM, and for how long.

In this case, the network has probably given you a 30 minute Periodic Tau interval, instead of the 10 minute interval requested by the device.

You can see what values the network gives you with the +CEREG (level 5), or %XMONITOR AT commands.

Best regards,

Didrik

[duxinglang]

Sorry，Sorry, I forgot to include the power screenshot of my PPK test, like this:  

I can confirm that currently the application does nothing to actively invoke network Settings or transfer data .

[Didrik Rokhaug]

The picture is a bit too zoomed out to really say what is going on, but my guess is that you see the periodic TAUs, and that the network has given you a period of 30 minutes.

You can use the AT commands I mentioned to verify this.

[duxinglang]

Thank you for your answer. I tried it with the AT command and the result is exactly the same:

%XMONITOR: 1,"","","46000","1D29",9,8,"0D1E2D42",11,3684,46,38,"","00000100","11100000","00111110".

The TAU time did change to 30 minutes and the active time to 8 seconds.  This leads to another problem: if my terminal needs to display the NB signal of the environment in real time, but the modem returns rrp is 255 during 30 minutes, how can I solve this problem?