LTE-M consuming way to much power to transmit 100 bytes UDP every 15 seconds, please help me understand why.

[EDLT]

I'm using the UDP sample from SDK 1.8.0 with the following modifications:

• No PSM
• No eDRX
• Send 100 bytes every 15 seconds

This is on the nrf9160-DK board.

I suspect I can improve power consumption by disabling RRC idle mode, but I cannot find any documentation on how to do this.

I am unsure of the actual cDRX timing parameters as what seems like DRX events are sporadic.

Here are some power profile images and a modem trace if that's helpful.

The above image shows large period of almost continuous activity after the TX event for ~5 seconds and then iDRX activity until the next TX event.

This is the activity while RRC connected. 

I am seeing an average of 10mA, with 22mA during the connection period. I was expecting the average current consumption to be 2.5 - 4mA.

7723.trace-2022-02-14T21-46-37.030Z.bin

[JONATHAN LL]

Hi,


What version of NCS are you on?

Regards,
Jonathan

[EDLT]

Hi Jonathan,

Version is 1.6.1.

Since posting this I was able to make significant improvement using RAI and socket options to get an early RRC release to idle. I guess I'm surprised most by the 2nd power profile image where the signaling is almost constant and there is no discernable/regular cDRX duration and inactivity period.

[EDLT]

Jonathan,

While awaiting an answer about what determines the cDRX duty cycle, I'm wondering if there is a way to know when the modem has finished sending all its data.

When using the RAI feature, if we send more than 600 bytes or so, I notice there are two outgoing transmissions. I imagine this is because the modem was not able to send out all data before we indicated there was not more data with the RAI_NO_DATA socket option.

If we can know when all the data has been transmitted, then I can better time the use of the RAI_NO_DATA option to conserve power.