PSM TAU and AT

[Mohammad Amin]

Hi, 

1. I have been trying to measure the current consumption of the development board of nRF9160 in PSM mode, however, until now I could have not understood the role of TAU and AT on the current consumption. According to "3GPP TS 24.008 Table 10.5.163a/3GPP TS 24.008" that is mentioned in the AT commands document, if bits 8-6 of Tracking area update(TAU) are set to "010", the timer unit will be 10 hours, however, the spikes time difference that I see does not change that much compared to the time when it is set to "001" which is one hour. I also am not sure about the role of AT too. Can anyone please explain this to me?

2. Is this possible to see if the nRF9160 is connected to the network through LTE or LTE-M?

3. I am using iBASIS and HOLOGRAM  IoT SIM cards that connect exactly to the same operator( Rogers), however, iBASIS shows a lot more power consumption than the HOLOGRAM. Why is this happening?

This is one of the current measurements I got:

[Sigurd]

Hi,

1)

For measuring current in PSM mode, I would recommend taking a look at this blog post.

The TAU is a mandatory procedure to do after waking up from PSM.

If you start to send data, while in PSM mode,  the device will wake up from PSM.

Also note that some networks does not support PSM yet!

I also am not sure about the role of AT too

What do you mean ? the role of AT commands ?

2)

through LTE or LTE-M?

The system mode is either NB-IoT or LTE-M, see this link.

 3)

a lot more power consumption than the HOLOGRAM

 How much difference ? Also see this comment. Are you on the same network for both sim cards? If it's a different network operator with the HOLOGRAM sim, it could be that only that network support PSM ?

[Mohammad Amin]

Hi, Thanks for responding.

1. I am using MQTT_simple example and I added "err=lte_lc_edrx_req(true)" to it right after "modem_configure" function. This example uses polling in a while loop to see if any data is received or not.

Does the device wake up from PSM after each polling? Do I need to enable PSM after each polling again?

I tried to enable PSM after each polling and then go to sleep using " k_sleep" and "k_cpu_idle", however, my power consumption has increased. I guess because every time for requesting PSM a large power is consumed. In this case, what are my options? Is only calling "err=lte_lc_edrx_req(true)" once before the while loop enough or I need to call it every time after each polling?

I checked this link and nmeasured the current based on the instructions and it works for me, however, in this tutorial in order to reduce the floor current, the serial peripheral has been disabled both from SPM and the main project. But I want to disable serial and other peripherals in the code whenever I want because I may need to interact with other sensors once in a while and therefore for that time I need the serial to be on. Is this possible to disable serial through the code and then go to sleep? I read this and this topic and it seems other ones want to disable the peripherals in the code too and no one answered them.

2. Thanks for the clarification.

3. Both HOLOGRAM and iBASIS connect to the same network(Rogers in Canada) but their power consumption is completely different and HOLOGRAM shows a lot less power consumption.

[Carl Richard]

Hi Mohammad!

We just ran into a somewhat similar issue, it's not resolved yet, but I can maybe provide some helpful info! We also use the iBasis card and have discovered that it forces the <Requested active time> value to 0, effectively disabling PSM. 

You can check if there is a difference in the PSM modes of your different providers by using the AT command AT+CPSMS? after activating PSM. (as stated in the AT Command documentation). It will return the parameters used.

Hope you can utilize this!

For reference: we are situated in Norway, so it could be a different situation.

- Carl

[Mohammad Amin]

Thanks. I used other sim cards and it seems they enter PSM mode.