cDRX- High current consumption

[nickagianFT]

Hi,

I've been trying to verify how much charge is needed to operate the nRF9160, so I did some measurements using the nRF9160-DK and the Power Profiler Kit II. I started with the recommended udp sample code (SDK version is 2.2.0). I could see that during the PSM mode, the consumption was as low as expected, but I found some inconsistencies regarding the eDRX phase, where the current profile looks different from what I've seen in other waveforms and tutorials (for example here https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/app_dev/optimizing/power.html) and consequently the average current draw is also higher. In the beginning, I had the iBASIS sim card and later changed to a local operator here in Denmark, in case the roaming mode was important, but I didn't see any changes in the power profile.

Have a look at this capture, which shows the whole transaction:

and then also a zoom-in to the eDRX phase:

I also have a modem trace file, if it helps: 1122.trace-2023-04-14T08-36-53.639Z.bin

My basic question is whether this behavior is just what the specific network here in Denmark does, therefore I can't do anything to improve it, or whether this is somehow hardware/software related and I can do something to bring the consumption down.

[Håkon Alseth]

Hi,

 

Thanks for sharing these details, as well as a modem trace.

The modem trace shows that these AT commands are set:

Sent AT Command: AT+CPSMS=1,,,"00000110","00000000"
Sent AT Command: AT+CEDRXS=3

This requests PSM with 0 seconds active time, and 60 minutes (6 * 10 minutes) tracking area update (TAU) timeout, which also is later accepted by the network itself, which is reflected by XMONITOR:

Rcvd AT Command: %XMONITOR: 1,"Telenor DK","Telenor DK","23802","5DE1",7,20,"027D2C0C",57,6200,53,32,"","00000000","00000110","01001001"

and the AT+CEDRXS=3 at command indicate that eDRX is disabled.

https://infocenter.nordicsemi.com/topic/ref_at_commands/REF/at_commands/nw_service/cedrxs_set.html?cp=2_1_7_3_0

 

The nRF91 uses approx. 9 seconds to initially connect to the network before you enter PSM.

 

If you are thinking of the cDRX period, that should be at the very end just before the current consumption goes to low uA area.

 

Kind regards,

Håkon

[nickagianFT]

Hi,

Thanks a lot for your answer.

Oops, I'm sorry. By mistake, I wrote eDRX but meant cDRX.

The behavior you are describing (PSM with 0 seconds active time, 60 minutes TAU timeout) is exactly what was intended. Great to confirm that the network accepted these requests.

Is this 9 seconds initial phase to connect to the network that you mention starting right after boot or a bit later, after the first short interval where the consumption drops really low?

Does that mean that all this long period in-between the long spikes the nRF91 is still trying to connect? I'm then a bit confused about how to identify the phases shown in the OPP.

I have also zoomed-in towards the end, before it goes to the uA-consumption area and it looks like this

Is this at the very end the cDRX? If yes, it looks very weird!

[Håkon Alseth]

Hi,

 

nickagianFT said:

Is this 9 seconds initial phase to connect to the network that you mention starting right after boot or a bit later, after the first short interval where the consumption drops really low?

Based on your original image, the window size is 10 seconds, and the total boot + enter PSM fits in between the window.

nickagianFT said:

Does that mean that all this long period in-between the long spikes the nRF91 is still trying to connect? I'm then a bit confused about how to identify the phases shown in the OPP.

That is your cDRX period, mixed in with the actual network traffic of the "udp" sample. The sample will do a DNS lookup and fetch NTP network time.

If you check out our power calculator:

 Online Power Profiler for LTE 

This has a preset for Telenor (Norway), which should be similar (but not exact) to how it behaves in your region.

 

Kind regards,

Håkon