Parameter meanings in 2022-05-04 LPWAN Coverage doc, PSM and eDRX columns?

[tedhavelka]

Hello Devzone,

My name is Ted, and I recently came across a 2022 May 4 LPWAN Coverage document on one of Nordic Semi's technical guides.  The specific guide is titled iBases ESIM International Coverage Update.  But I am confused by the meaning of the value pairs in the right most four columns.  Looks like these are in units of seconds, which makes sense for at least the two columns number 9 and 10 from left, where "PSM T3412 and T3324" appears above these columns.

What do these values represent?  Are these maximum supported timer periods, and shorter periods are possible?  In what way do these values define which periodic Tracking Area Update (periodic-TAU), Active Time and eDRX values we can expect to be granted in our given geographies?

Some background to these questions:

I've posted some related tickets to this question recently:  87176, 87451, 87734, but I am still having trouble obtaining any non-zero T3412 and T3324 timer values.  I'm working in a large metropolitan area with population of roughly two million, between Seattle and the Bay Area on United States west coast.  At least one of the major Mobile Network Operators listed in the United States rows of the LPWAN coverage document operates in our city.  Given this I surmise that at least for LTE-M type network registration I should be able to see my nRF9160 based device be granted some valid periodic-TAU and Active Time values.

Per ticket 87451 I am performing the AT command sequence to first turn off modem, then request a PSM, then turn modem on:

AT+CFUN=0

AT+CPSMS=1,,,"00010010","00001111"   . . . periodic-TAU of 180 minutes, active time ( 2 sec * 15 ) = 30 seconds

AT+CFUN=1

Entering these commands by hand there is plenty of delay, so I am confident the modem is off by the time I enter my PSM values to request from the MNO.  I check modem status and granted values as per the above linked Devzone tickets, namely by issuuing AT+CFUN?, AT+CEREG=5 followed by AT+CEREG?, AT%XMONITOR.  Command AT+CGDCONT? tells me whether my device registered with any network or not.  I almost never see either full name or short name of the MNO, two parameters which AT%XMONITOR returns.

I have tried multiple different values for periodic-TAU and Active Time.  I'm searching for ones which local MNO will grant.

Command AT+CEREG? consistently returns "11100000", "11100000" as its last two fields.  This looks like bad news to me.  Until I can learn correct AT command sequence, and confirm or disconfirm local network provider support I cannot enjoy the battery-enabling low power support touted as one of the nRF9160's greatest design features.  All clarifying help to these questions appreciated!

- Ted

[Albrecht Markus Schellenberger]

Hello Ted,

tedhavelka said:

If I must operate without PSM, could I still achieve a daily average current draw less than 10 uA?

I unfortunately will not be able to give you a universal answer here, as this depends on a lot of factors, starting with the environment the nRF9160 is surrounded with and how well functionality of the application is adapted to the respective use case.

PSM and thus, optimising power consumption is a challenging topic. It can not be fully investigated on paper in advance, so testing and verification along the way is required. As already mentioned, a good starting point could be to talk to the carrier to receive concrete details about if and how PSM is allowed for connecting devices in different tracking areas.

Since iBasis is a MVNO, meaning UE’s with their SIM card will connect to a carrier based on a roaming contract, talking to the carriers itself should be considered as well. Possibly, they can offer you a subscription that suits better to your specific use case.

tedhavelka said:

Best I open another Devzone ticket to ask about this fallback strategy, when PSM is not available?

Yes, you are welcome to do so.

Regards,

Markus