nRf9160 PSM measurement

[Coyote73]

Hello, i currently evalutate LTE-M for my company and i run into a lot of trouble for starting the test. But at least i have able to do the test

I have cut a lot of code from the AssetTracker example, mainly the software connect modem to the network ( using lte_lc_init_and_connect ) and go to sleep for 10 sec (and blink some led)

After successful connexion , i call lte_lc_psm_req(true) and then use the command  AT+CPSMS? to read back that the PTAU and active time is set correctly (and it is the case). My software never send something it only go to sleep.

Application started                                                             
LTE LC config ...                                                               
recv: +CEREG: 2,"01C3","00A8FE04",7,0,0,"11100000","11100000"                   
recv: +CEREG: 1,"01C3","00A8FE04",7,,,"00001000","11100000"                     
PSM set to true                                                                 
+CPSMS: 1,,,"10100010","00000110"                                               

With such value i expect to have a  TAU every 2 minutes with an active time of 12 secondes.

BUT current measurement doesn't show this, i have run my software recording current consomption for one hour and i have the following results:

Details , board start, connect to network, set PSM and go to sleep: 

Details 2 : After sleeping 53m44s a supposed TAU is done (and active time is around 14 sec)

<Test Setup>

- DK v0.8.5 (SB43 cut) ,power supply is a 3.6V source connected on P28

- modem firmware v1.0.1

- ncs tag; v1.0.0

- current measurement tool: multimeter Agilent 34465A connected on P24 (pin 1 and 2), calibre 1A

- Sim cards tested : iBasis and Orange

-Country : France (so i suppose iBasis is roamed on Orange network)

-LTE_PCO_LEGACY = n

My questions is : 

Does the details 2 screenshot show current involved in PTAU as supposed ?

If yes, why the PTAU is effectued around 54 minutes after i put the board in sleep and not every 2 minutes as requested (and agreed with network i do the read 10 secondes after connexion) ?

Any idea that can help me to understood is welcome

[Amanda Hsieh]

Hi, 

Does the details 2 screenshot show current involved in PTAU as supposed ?

Please see this post.  

If yes, why the PTAU is effectued around 54 minutes after i put the board in sleep and not every 2 minutes as requested (and agreed with network i do the read 10 secondes after connexion) ?

If you call AT+CEREG=5 followed by AT+CEREG? you should get the actual PSM-interval from the network.

-Amanda H.

 

 

[Coyote73]

Thanks for your feedback, i have totaly messed up with CPMS command that it's only show requested value and not current value.

Now i have

+CPSMS: 1,,,"10100010","00000110"
+CEREG: 5,1,"01C3","00A8FE04",7,,,"00001000","11100000"

So 16 sec active time but periodic TAU is disabled, i will contact my network provider who as informed me that PTAU is effective on its network but in fact...seem not to be.

Regards

[Amanda Hsieh]

Yes, you are right. 

The two last values of the CEREG level 5 response are the ones related to PSM, Active-Time (the time after a transmit event when the device is reachable) and Periodic-TAU (the time between regular transmit events to keep the connection alive).

The meaning of the values can be found in 3GPP TS 24.008, section 10.5.7.4, but long story short, when they start with "111" the timers are not active, i.e. you do not have PSM activated.

-Amanda H.

[Coyote73]

I have a talk with a technical person in charge of LTE-M in France and it said that PSM is available (but my test show the opposit), so, have you any tricks to allow me to have some debug information from nrf9160 modem that i can send to him to investigate what happened and why timer is shown as disabled ?

Have you ever heard about other customer that have succefully used PSM in france ?