Transmit power used - Verizon vs AT&T

[Joshua]

In our use case we are using the nRF9160 in eDRX mode with an eDRX interval of 40.96sec. 

I'm noticing that the power required to transmit a message varies widely between AT&T and Verizon.  Both networks require about 9 seconds to transmit the message and return to sleep. 

On Verizon after the initial transmit, the nRF9160 remains at a fairly constant ~45mA for the reminder of the time.  

On AT&T after the initial transmit, the nRF9160 current varies between ~100uA and ~45mA.  It appears that the timing is about 280ms sleep, then 80ms on which repeats for the reminder of the 9seconds. 

The average power on AT&T is therefore much lower and being a battery powered device this is important. 

Attached are two screen captures of the current into the device when sending a packet.  Note that the sample speed of this capture is not fast enough to fully capture all points, but you can clearly see the difference I'm talking about. 

Is this expected behavior?  

Are there settings available to adjust this behavior? 

We are looking to send messages at the lowest possible power. 

[Stian Røed Hafskjold]

Hi, this is probably because of the eDRX interval in RRC connected mode (aka cDRX). I'm guessing that in the AT&T network you have a cDRX interval of 0.32 seconds which seems to be the standard, and in the Verizon network it's a lot faster. You should check with the network operator and get the parameters they are using in your region, and check if it's possible to request a different interval. Other than that it could be NB-IoT vs M1, but it looks to me that both plots are showing M1? NB-IoT has a slower transfer rate and the radio is powered on for a longer time each interval.

[Joshua]

Hi Stain,  I will reach out to Verizon and see if this is a configurable parameter.  

In general is it expected that a data transmission would take a total of about 9 seconds?  This seems like a very long time and if we are able to reduce this time it would greatly improve our battery life. 

[Stian Røed Hafskjold]

This is another network parameter. RRC connection timeout, or cDRX timeout. You can ask if this is configurable as well.

[jbrzozoski]

Is there any way to tell from the application layer what cDRX setting is in use?  We'd like to be able to see it, even if we can't control it.

[Stian Røed Hafskjold]

Sorry, that's not possible. You can do a modem trace and send it to us for analysis: https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/how-to-get-modem-trace-using-trace-collector-in-nrf-connect