Modem open after ended transmission

RE: Modem open after ended transmission

Håkon Alseth — Tue, 11 Feb 2020 14:09:36 GMT

Hi Andreas,

Thank you for being this patient. I dug deeper into this, and soon figured out that I needed to consult experts.

I have asked the developers and designers internally, and there is a RRC idle + release happening after the tracking area update performed after the T3412 (sleep timer) expires and before the T3324 (active timer) starts. The time you're in this RRC Idle, ie before the RRC release is issued, is a value set by the eNB (network). Any active time will be executed after this. Judging from the plots, it looks like approx. 30 seconds is the specific period in the network you're connected to.

Kind regards,

Håkon

RE: Modem open after ended transmission

thireo — Tue, 11 Feb 2020 10:29:16 GMT

I have just done the following with a Telenor IoT SIM-card and using the AT client sample application.

AT+CFUN=1 - Power on modem
AT+CPSMS=1,,,"00100001","00000001" - request 2 seconds active time and 1 hour Tau.
AT+CEREG=5 - Enabling reporting
AT+CEREG? - Poll for report.

See the attached image for the response.

RE: Modem open after ended transmission

Håkon Alseth — Tue, 11 Feb 2020 10:03:39 GMT

Hi Andreas,

In the telenor network here in norway, I cannot get such a low active time as you currently have. It is therefore very important that you check the PSM intervals that are set by the network (not just requested by the nRF).

By setting AT+CFUN=1, then inputting your PSM settings via AT+CPSMS=1,,,"TAU","ACTIVE-time", you should soon get a PSM from the network.

Using AT+CEREG=5 to enable reporting the PSM intervals, and check with "AT+CEREG?"

Kind regards,

Håkon

RE: Modem open after ended transmission

thireo — Tue, 11 Feb 2020 09:41:09 GMT

Hi Håkon

I double checked if GPS is being enabled, by polling the system mode. I can confirm, that it is not being enabled.

Oh okay, I misunderstood you then. I'm still unsure how I should test with the AT_client application.

I have just tested with both SIM-cards and they show similar results.

Best regards,
Andreas

RE: Modem open after ended transmission

Håkon Alseth — Tue, 11 Feb 2020 09:02:59 GMT

Hi Andreas,

[quote user="thireo"]Could you give me some pointers as to how I'm supposed to send data via AT commands. I have yet to find any information regarding this, in the datasheets for NRF9160.[/quote]

You cannot trigger sending or receiving IP data using the AT commands that the modem exposes.

I wanted to see if this happens due to the application triggers sending of data, or if this is a returned active time in PSM that differs.

You mention that you have two SIM cards from different vendors (Telia and Telenor). Do both of these behave similar?

Kind regards,

Håkon

RE: Modem open after ended transmission

thireo — Tue, 11 Feb 2020 08:52:42 GMT

Hi Håkon

No GPS is not enabled. At least not that I'm aware of. In prj.conf systemmode is set to "CONFIG_LTE_NETWORK_MODE_NBIOT".
The build generated .config file for zephyr seems to confirm my assumption:
"# CONFIG_LTE_NETWORK_MODE_LTE_M is not set
# CONFIG_LTE_NETWORK_MODE_LTE_M_GPS is not set
CONFIG_LTE_NETWORK_MODE_NBIOT=y
# CONFIG_LTE_NETWORK_MODE_NBIOT_GPS is not set"

Could you give me some pointers as to how I'm supposed to send data via AT commands. I have yet to find any information regarding this, in the datasheets for NRF9160.

Best regards,
Andreas

RE: Modem open after ended transmission

Håkon Alseth — Mon, 10 Feb 2020 11:42:54 GMT

Hi Andreas,

Are you enabling the GPS? That will also draw 30 to 40 mA (depending on what the CPU is up to)

Could you try the same setup with at_client and see if this also behaves similar?

There are delays in terms of when asset_tracker sends data, especially when GPS is enabled, as the GPS only runs when in PSM or eDRX mode.

Kind regards,

Håkon

RE: Modem open after ended transmission

thireo — Thu, 06 Feb 2020 10:49:13 GMT

Hi Håkon

I have just double checked the results from my CEREG requests. It responds with:
+CEREG: 5,1,"61B4","02781248",9,,,"00000001","00000110"

Which from my interpretation should equal to 2 seconds active time and 3600 seconds sleep period.

Enabling LTE control debugging seems to confirm this:
"[00:04:11.449,127] <dbg> lte_lc.lte_lc_psm_get: TAU: 3600 sec, active time: 2 sec"

Best regards,
Andreas

RE: Modem open after ended transmission

Håkon Alseth — Thu, 06 Feb 2020 10:36:05 GMT

Hi Andreas,

Thanks for the detailed scope.

It looks like your current active time is approx. 30 seconds.

Does this correlate with the return from CEREG?

I see now that I have flipped the former return values from CEREG.

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

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

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

Kind regards,

Håkon

RE: Modem open after ended transmission

thireo — Thu, 06 Feb 2020 08:47:57 GMT

Hi Håkon

I finally got the DMM6500 to do what's supposed to. Please see the attached figure for a complete cycle.

And yes, I'm still seeing unwanted behaviour.

Best regards,
Andreas

RE: Modem open after ended transmission

Håkon Alseth — Wed, 05 Feb 2020 15:35:38 GMT

Hi Andreas,

Hard to see how long that RX period is, as the instrument does not log before 0854, but it seems to already be 6 seconds.

You still see unwanted behavior?

Kind regards,

Håkon

RE: Modem open after ended transmission

thireo — Wed, 05 Feb 2020 12:16:16 GMT

Hi again

I had some trouble getting the data from the measuring unit. But it seems you may be right regarding the TX peaks. The picture below depicts the modem idle current of ~30mA, a TX peak and afterwards the modem off period. The measurement was done with the PSM RPTAU set to 1 hour.

Best regards,
Andreas

RE: Modem open after ended transmission

Håkon Alseth — Tue, 04 Feb 2020 13:07:23 GMT

Do you have a detailed view of the current consumption? TCP will do a 3-way handshake, and nb-iot is not the speediest transport layer, so it would be interesting to see if there's any TX peaks.

Could you try to set the PSM RPTAU (sleep) interval higher, let's say 30 minutes? If you set 2 minutes, and start an application timer of 2 minutes, you might get into a scenario where the application timer drifts in time (lets say 2 minutes and 10 sec), where you get two TAU back-to-back.

To avoid this scenario, a workaround is to set the PSM high. Or set the application timer below the PSM TAU interval.

Kind regards,

Håkon

RE: Modem open after ended transmission

thireo — Tue, 04 Feb 2020 12:38:43 GMT

Hi Håkon

The requested TAU is set to two minutes (0b10000100) and active time is set to 6 seconds (0b0000011). Both have been confirmed and acknowledged by the network. By polling AT+CEREG and by enabling LTE_LINK_CONTROL_LOG_LEVEL_DBG in Zephyr.

The Thingy:91 is located in Denmark and is using a Telia/Telenor NB-IoT SIM-card provided. They have also confirmed that no restrictions are set for PSM on their network.

Best regards,
Andreas

RE: Modem open after ended transmission

Håkon Alseth — Tue, 04 Feb 2020 11:40:11 GMT

Hi,

[quote user=""]The current consumption is high (~30+mA) for at least 20 seconds after transmission has been completed[/quote]

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