Modem Reset Loop Restriction Reset

[Sashi]

Use case:

A moving NRF9160 modem often needs to connect and retry many times in normal operation. there are some cases where they are towers, but not allowed on them. etc. As well as conditions where you are minimally connected to a tower due to poor signal, but must use whatever signal you have to send data. 

Question:

What is the recommended strategy to maintain maximum connected state on moving devices that go between different towers/ providers/states/etc over long periods of operating time of fielded hardware.    

taking into account the modem reset loop https://docs.nordicsemi.com/bundle/nwp_042/page/WP/nwp_042/intro.html where you may be traveling with a very weak signal and dropping in and out of connection often. 

Partially related to:

 RE: Is there a way to truly hard reset the nRF9160 without power cycling? 

[Sashi]

This will be very helpful. thanks

I want to understand what is the best way to handle this case
A device is placed at a location that has like 1 bar cell connection. The device can connect but the connection is poor. This device is fixed at this location and doesn't move. additionally the device is always supplied with USB power so we don't care about power consumption.  Data is sent every 1-10 minutes (programable) 

Currently, we must reboot the device externally to allow it to stay connected 24/7 once we detect that it no long can connect. 

I think we are fine with constantly toggling going off and online every minute as we need to send data, but not sure if this preferred behavior that the cell provider wants to see.    
Please advice on the best way the nrf91 should be used to handle fixed installations with unlimited power and weak signals. 

[Sashi]

additionally is is recommended, if we have an accelerometer to detect motion, that we toggle %REDMOB  between mobility and stationary mode dynamically?   This would be for a generally mobile application, but when a device stops moving it will rest there for several hours to days.   

[Charlie]

Hi Sashi,

Sashi said:

Currently, we must reboot the device externally to allow it to stay connected 24/7 once we detect that it no long can connect. 

Sashi said:

Please advice on the best way the nrf91 should be used to handle fixed installations with unlimited power and weak signals. 

For this fixed installation device, it seems reboot deice will help to improve cellular network connection according to your experience. If it is the truth, I think you can set a timer to control the reboot happens no more than 6 timers per 30 minutes. This can ensure you have at least 5 minutes interval to send data. But I would suggest work on the direction to improve connection instead of play trick with Modem Reset Loop Restriction Reset. Here are some suggestions:

1. Use NB-IoT network instead of LTE-M if possible. 
2. Modify hardware design to improve antenna performance.
3. Switch to operator with better coverage in this area, even other cellular connection method like 4G, 5G.
4. Switch to other connection technology like DECT NR+, LoRa to extend connection range or the device.

Sashi said:

if we have an accelerometer to detect motion, that we toggle %REDMOB  between mobility and stationary mode dynamically?   This would be for a generally mobile application, but when a device stops moving it will rest there for several hours to days.   

Yes, you can use the accelerometer to detect motion and dynamically toggle the %REDMOB command between mobility and stationary mode. This is particularly useful for applications where a device is generally mobile but may rest in one place for several hours to days.

The main benefits of enabling the Nordic-proprietary reduced mobility feature are:

1. Reduced Power Consumption: By limiting the swapping between cells in stationary use cases, the device can save power, which is crucial for battery-operated devices.
2. Stable Connectivity: The device stays connected to the same base station, avoiding the power consumption penalty of switching to a different base station and back. This can help maintain a stable connection, especially in scenarios where there might be a temporary drop in link quality to the closest base station.

You can use this feature if you think your application will benefit from it.

Best regards,

Charlie