nRF91 no cellular service power consumption

[droberson]

To preface:

• Board: Custom with nRF9151 module
• nRF Connect SDK / Toolchain: 3.1.0
• Modem Firmware 2.0.3
• PSM enabled
• Propriety PSM enabled (Enables fallback for when cell network doesn't support / grant regular PSM)
• eDRX disabled
• RAI enabled
• Carrier: Verizon

Hello,

I am testing modem power consumption in the scenario where the modem does not have cellular service (CEREG: 4). Essentially, I am disconnecting the antenna from our board to simulate this scenario. A shield box would also achieve the same results. These are my current measurement results:

This is on a custom board so the currents won't match a nRF9151DK exactly, but the takeaway is that the modem stays in a periodic high-current on state while searching for a network indefinitely it seems. I have only monitored this condition for 10-15 minutes with the power profiler kit 2. Based on the above, I have a few questions:

1. Does Nordic employ any power saving techniques when the nRF9151 module doesn't have cellular service (Out of coverage)? If so, what are they?

2. If the answer to #1 is no, then I assume it is up to the developer (me) to implement my own power saving techniques in the event of no cellular service?

Thanks,

Derek

[Øyvind]

Hello Derek, 

1. Does Nordic employ any power saving techniques when the nRF9151 module doesn't have cellular service (Out of coverage)? If so, what are they?

Yes, we do have some functionality that could be perfect for your use-case: Feature configuration %FEACONF - Disable paging reception in cells without usable service. From the documentation: 

This feature can be used to stop the modem from remaining on a cell that does not permit service. When allowed networks are not found, the modem transitions to a power saving state and runs the configured periodic searches until an acceptable network is detected. This helps reduce battery usage under limited service conditions.

Please have a look at that functionality and let me know how that works in your test case?

Kind regards,
Øyvind

[droberson]

Hey Øyvind,

Thanks for your reply! That is a neat and useful feature, but I don't think it applies to my specific test case. To confirm, I tested this feature by adding AT%FEACONF=0,4,1 to my modem power on routine. My current measurement results are exactly the same as without this configuration as seen below.

I queried the modem to make sure FEACONF=0,4,1 is set, and this is what I get:

ATCMD_PROC: (cli) Executing: AT%FEACONF=1,4
ATCMD_PROC: (cli) Response: %FEACONF: 4,1

I also confirmed I am running mfw_nrf91x1_2.0.3.

Looking at the name of this feature in the AT command document, it says "Disable paging reception in cells without usable service". This implies that it addresses the condition of when the modem is connected to a cell (tower) that doesn't have active service. The condition I am testing is when the modem is not connected to any cell and thus doesn't have service.

Am I missing something?

Thanks,

Derek

[droberson]

Hey Øyvind 

Any comment on my last reply?

Thanks

Derek

[Øyvind]

Hi Derek, my sincere apologies for the late reply.  My answer did not get sent last week.

Our modem team points out that AT%FEACONF will improve the power saving in very low signal conditions where it’s easy to lose the serving cell. Also, adding Periodic cell search configuration AT%PERIODICSEARCHCONF will provide ready made configs for ultra low power. i.e. 

• AT%FEACONF --> Improves power efficiency in scenarios with very weak signal strength, where the serving cell can easily be lost.

• AT%PERIODICSEARCHCONF --> Provides predefined configurations for ultra-low-power operation by controlling periodic cell search intervals, and designed for cases where no cells or service are available.

Data profile %XDATAPRFL (tied to above mentioned periodicsearch), i.e. more generic command that adjusts various modem operations based on the requested setting.
Note:  XDATAPRFL command modifies the PERIODICSEARCH settings based on the selected profile

AT+CFUN=2 -  Sets the device to receive only functionality. Can be used for operations that do not require TX, such as network search for connection readiness, Evaluating connection parameters %CONEVAL, Environment evaluation %ENVEVAL, and Neighboring cell measurement and notification %NCELLMEAS

• Supports network search, selection, and notifications while in Rx-only mode.

• Enables +CEREG and %MDMEV SEARCH STATUS reporting.

• Allows all AT commands that do not require transmission capability.

• Adds support for AT%NCELLMEAS and improves AT%CONEVAL performance in this mode.

Consider CFUN=4 (Flight Mode) if the ULTRA_LOW_POWER configuration does not meet requirements IF e.g. ULTRA_LOW_POWER configuration example is not meeting the requirements: AT%PERIODICSEARCHCONF=0,0,0,1,"0,10,40,,5","1,300,600,1800,1800,3600"'

This sets modem search intervals before entering power-save cycles.
Note: Flight mode shutdown must be handled by the application. Additional app-side logic is required if minimizing current consumption is critical.

Let me know how that works for you!

Kind regards,
Øyvind

[droberson]

Hey Øyvind,

No worries, thanks for the update! This is very good information, thank you. I tested XDATAPRFL using the "Ultra-low power" mode and current consumptions are much better (Less periodic searching). I see that this can be further tuned with the PERIODICSEARCHCONF command. I will discuss this with our customer in a meeting later this week. Assuming I have no additional questions at that time, I will close this ticket.

Thanks!

Derek

[Øyvind]

Hi Derek, happy to help! Please reopen this ticket by posting your questions, if you have any :) 

Kind regards,
Øyvind