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Modem open after ended transmission

thireo

Dear Devzone

I have an NB-IoT application running on a Thingy:91, that wakes up every two minutes and sends a small package over TCP to a remote server.  
I'm using a Keithley DMM6500 to measure the current consumption, and from that it is clearly visible that the modem doesn't not power down after sending the data. The current consumption is high (~30+mA) for at least 20 seconds after transmission has been completed. This of course ruins the average current consumption.
I have tried using different Power Saving Modes (PSM) with an active time as low as possible (a couple of seconds). The PSM mode is accepted by the network, but does not change the described behaviour. I have also tried different network vendors but without success.

I see similar behaviour when using the Asset Tracker example project.

Is this intended behaviour?

Modem firmware: 1.1.0

Best Regards, Andreas (Thireo)

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  • 0

    Hi,

     

    The current consumption is high (~30+mA) for at least 20 seconds after transmission has been completed

    PSM has two components, one requested TAU (the sleep period) and the requested active time (active time after TAU).

    The lowest period for both these are different for every network provider. In norway, I get this back from AT+CEREG? (enable PSM intervals by issuing AT+CEREG=5 first):

    +CEREG: 1,"76C1","014A0305",7,,,"00100001","00000110"

    *edit: this was initially parsed wrong, as I read CEREG return Active time as TAU (and vice-versa)* 

    Incorrect parsing:

    This translates to 1 hour sleep (001 00001 -> GPRS timer 3), and 6 seconds (000 00110 -> GPRS timer 2) of active time after TAU.

    Correct parsing:

    +CEREG: 1,"76C1","014A0305",7,,,"00100001","00000110"

    00100001 is the active time, 001 = minute, 1 * 1 minute is your active time.

    00000110 is the TAU (sleep period), 000 = 10 minutes, 10 min * 6 = 1 hour, is the sleep period.

    *edit finished*

    If you have a larger active time, try to request a lower active time by setting "CONFIG_LTE_PSM_REQ_RAT="00000110"" in your prj.conf file.

    This will then request 6 seconds, but note that this is ultimately driven by the network, so be sure to check your returned PSM intervals using AT+CEREG=5 and AT+CEREG?.

     

    Kind regards,

    Håkon

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  • 0

    Hi,

     

    The current consumption is high (~30+mA) for at least 20 seconds after transmission has been completed

    PSM has two components, one requested TAU (the sleep period) and the requested active time (active time after TAU).

    The lowest period for both these are different for every network provider. In norway, I get this back from AT+CEREG? (enable PSM intervals by issuing AT+CEREG=5 first):

    +CEREG: 1,"76C1","014A0305",7,,,"00100001","00000110"

    *edit: this was initially parsed wrong, as I read CEREG return Active time as TAU (and vice-versa)* 

    Incorrect parsing:

    This translates to 1 hour sleep (001 00001 -> GPRS timer 3), and 6 seconds (000 00110 -> GPRS timer 2) of active time after TAU.

    Correct parsing:

    +CEREG: 1,"76C1","014A0305",7,,,"00100001","00000110"

    00100001 is the active time, 001 = minute, 1 * 1 minute is your active time.

    00000110 is the TAU (sleep period), 000 = 10 minutes, 10 min * 6 = 1 hour, is the sleep period.

    *edit finished*

    If you have a larger active time, try to request a lower active time by setting "CONFIG_LTE_PSM_REQ_RAT="00000110"" in your prj.conf file.

    This will then request 6 seconds, but note that this is ultimately driven by the network, so be sure to check your returned PSM intervals using AT+CEREG=5 and AT+CEREG?.

     

    Kind regards,

    Håkon

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