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  • Case ID: 344489
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NRF9161 based LTE-M tracker data drops while moving – can it be optimized?

marsal

Hi everyone,

I’m using a custom board (a tracker) that can travel at speeds up to 65 km/h and transmits data regularly every 200 ms. I expect, therefore, that the inactivity timer should not be activated. While the device is in motion, I’m seeing intermittent data gaps ranging up to several seconds, which is unacceptable for our application.

Could this be caused by non-optimal cell-handover settings? I’ve attached a few logs below for reference.

Any suggestions would be greatly appreciated.

Thanks,
Martin

 

Three log fragments examples, related to data send drops:

 

17:31:57.179 +CSCON: 0

17:31:57.230 <inf> main: RRC mode: Idle

17:31:57.276 +CEREG: 1,"04D3","0DBC2351",7,,,"11100000","11100000"

17:31:57.298 <inf> main: Cell update, cell tac: 1235, cell id: 230433617

17:31:57.371 +CSCON: 1

17:31:57.429 <inf> main: RRC mode: Connected

17:31:57.539 +CSCON: 0

17:31:57.568 <inf> main: RRC mode: Idle

17:31:57.907 +CSCON: 1

17:31:57.926 <inf> main: RRC mode: Connected

***

17:37:54.095 +CEREG: 1,"04D3","0DC18750",7,,,"11100000","11100000"

17:37:54.154 [00:54:10.770,263] <inf> main: Cell update, cell tac: 1235, cell id: 230786896

***

17:38:05.373 +CEREG: 1,"04D3","0DDD4350",7,,,"11100000","11100000"

17:38:05.434 <inf> main: Cell update, cell tac: 1235, cell id: 232604496

***

 

Modem firmware: mfw_nrf91x1_2.0.2

 

Current 9161 modem initiation sequence is:

 

AT+CFUN=0

AT%XSYSTEMMODE=1,0,0,0

AT+CPSMS=0

AT+CEDRXS=0

AT%RAI=0

AT+CSCON=1

AT+CEREG=5

AT+CFUN=1

Parents
  • 0
    marsal said:
    I’m seeing intermittent data gaps ranging up to several seconds, which is unacceptable for our application.
    marsal said:
    5 Hz to an MQTT broker

    You chose MQTT. That usually queues the messages and transmit them, when transmission is possible. So, there may be a short gap in the time-stream, but not the data-stream, that's just delayed. If you add the "sensor-time" to the data, you will also be able to have the time-stream available with delays.

    I guess, you need to adapt your application to that common practice.

  • 0 in reply to Achim Kraus

    Thanks, well, my interval_between_two_subsequent_successful_mqtt_sends is between 210ms and 300ms in case that there are no cell updates, which is OK for me. When cell update comes, it raises to e.g. 1.5 sec. So the cell update seems really be the case.

    Er, I am struggling just now to catch the modem trace... Not sure if UART or RTT approach is better for me. 2.6.3.

  • 0 in reply to dejans

    Thanks, dejans, a lot!

    Well, the best case could be that the descibed changes could have improved the behavior described in the very first email.

    I have made the changes described in the previous email with trace link and only then I was recording the trace. Before the change, at the same path, I had observed number of cell switch changes with 1-2 secs data transfer breaks. In general, my question would be if the described settings are OK and/or what could be done more. Big thanks again.

  • 0 in reply to marsal

    Hi Martin,

    marsal said:
    In general, my question would be if the described settings are OK and/or what could be done more.

    Connection re-establishment is triggered due to sync loss to serving cell (T310 expiry). This is normal operation for moving UE. Data paths are suspended for time of connection re-establishment. Parameters which control re-establishment are given by the network. There is nothing which could be done from UE side to avoid this interruption. You could contact the carrier regarding network support for LTE-M handover.

    Best regards,
    Dejan

  • 0 in reply to dejans

    Let me still ask: does this meant the the network doesn't work in "Connected" mode for LTE-M (Rev14)? Or should I somehow set nrf9161 to allow this? Thanks again!

  • +1 in reply to marsal

    Hi Martin,

    There is nothing on UE side which could be done to improve your use case. Everything is up to network configuration.

    Network works in connected mode, but it could maintain connection better if it would support handover. You should contact the carrier and ask whether they support handover for LTE-M. Overall handover is controlled by the network and UE cannot do anything to trigger it.

    UE can only try connection re-establishment for recovering connection problems which might cause too long delay for data transmission with regard to your requirements.

    Best regards,
    Dejan

Reply
  • +1 in reply to marsal

    Hi Martin,

    There is nothing on UE side which could be done to improve your use case. Everything is up to network configuration.

    Network works in connected mode, but it could maintain connection better if it would support handover. You should contact the carrier and ask whether they support handover for LTE-M. Overall handover is controlled by the network and UE cannot do anything to trigger it.

    UE can only try connection re-establishment for recovering connection problems which might cause too long delay for data transmission with regard to your requirements.

    Best regards,
    Dejan

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