Enable NB-IOT and LTE-M at the same time

[Giannis Anastasopoulos]

Dear All,

I am building an application that needs to use NB-IOT and if that is not available then use LTE-M.

I tried sending this AT Command:

AT%XSYSTEMMODE=1,1,0,2

But this returns an error.

What I noticed is that if I enable both NB and LTE-M this command returns ERROR.

So I would like to ask if there is any way to achieve the following behaviour:

Check for NB-IOT network and if there is no connection to such network turn to LTE-M

Thank you all.

[Didrik Rokhaug]

Hi.

At the moment, only one LTE mode is supported at the time. See this note from the AT command documentation:

Note: Only one supported LTE mode allowed at a time. This command is allowed only before activating the modem using the CFUN=1 command. If the mode needs to be changed, the modem must first be set to flight mode using the CFUN=4 command.

However, the lte_lc driver will by default switch mode if it is not able to establish a connection. You can control this behavior with the CONFIG_LTE_NETWORK_USE_FALLBACK and LTE_NETWORK_TIMEOUT configuration options.

Best regards,

Didrik

[Leonard_Ch]

Hello Didrik :)

I'm also considering using both the NB_IOT and LTE-M capabilities of the nRF9160 at the same time. It can be something like LTE-M active until I meet a wall the signal doesn't pass through for example, then switch to NB_IOT, or simply like the example above where I will use the option with available network . Does the NRF9160 support both modes at the same time?  

BR,

Leonard

[Didrik Rokhaug]

Hi Leonard_Ch.

Not much has happened on this front since my last reply, so the nRF91 still only supports one mode at a time.

You can of course still disconnect from the network (AT+CFUN=4), change system mode (AT%XSYSTEMMODE=...), and then try to connect to the network again (AT+CFUN=1).

But, the lte_lc library will still use the other mode as a fallback if enabled. Note that the lte_lc library only controls the initial connect, it will not monitor the connection afterward in case of loss of service.

Best regards,

Didrik