Neighbor cell measurement VS Radio technology

[Vincent44]

Hello,

I have a question concerning the neighbor cell measurement feature on my nRF9160.

After some tests, it seems to be sensitive to the operation mode. For example, on the prototype sitting on my desk, in an urban area:

nrf_modem_at_printf("AT%%XSYSTEMMODE=1,1,0,2") // Prefered NB-IoT
nrf_modem_at_printf("AT+CFUN=1") ;
params.search_type = LTE_LC_NEIGHBOR_SEARCH_TYPE_GCI_EXTENDED_COMPLETE ;
params.gci_count = 5 ;
lte_lc_neighbor_cell_measurement(&params);

Gives me a result in ~250 sec

nrf_modem_at_printf("AT%%XSYSTEMMODE=1,1,0,0") // Prefered Auto
nrf_modem_at_printf("AT+CFUN=1") ;
params.search_type = LTE_LC_NEIGHBOR_SEARCH_TYPE_GCI_EXTENDED_COMPLETE ;
params.gci_count = 5 ;
lte_lc_neighbor_cell_measurement(&params);

Gives me a result in ~60 sec

On both cases, I am getting similar results with 2 different MCC-MNC. I suspect that there are indeed two operator providing LTE-M and NB-IoT in my location, but I can not be sure ...

Question is : Does the neighbor search scan for all available cells, LTE-M and NB-IoT, no matter on how XSYSTEMODE was set ?

If so, is there a way to distinguish LTE-M from NB-IoT cells ?

Thanks.

[Simon D-M]

Hi,

Does the neighbor search scan for all available cells, LTE-M and NB-IoT, no matter on how XSYSTEMODE was set ?

the AT command is structured as follows : 

%XSYSTEMMODE=<LTE_M_support>,<NB_IoT_support>,<GNSS_support>,<LTE_preference> (link to the doc)

So if you only set the "preference" it will check for both. But if you remove unset of the "support" it will only look for the remaining protocol.

If so, is there a way to distinguish LTE-M from NB-IoT cells ?

You should be able to see what your device is using with the Cellular Monitor application (from nRF connect for desktop) under the "ACT" field.

If you don't know how to use this app, I would recommend you taking the Cellular IoT Fundamental course on DevAcademy. It is briefly explained here.

You should also be able to get that information with the AT-command "AT+CEREG?". If you don't know how to use the AT-commands, it is also explained in the DevAcademy course (here).

Best regards,

Simon D-M

[Vincent44]

Hello,

Thanks for your response.

Maybe my question was not very clear.

I am not trying to force the device to use LTE-M or NB-IoT to connect to the network. I am also not trying to retreive the info of which network the device is currently connected to.

What I am trying to acheive is a list of surrouding cell towers, using the neighbor search feature.

- Will I get the same results, no matter of XSYSTEMMODE ? For example, I noticed that AT+COPS=? works differently wether NB-IoT or LTE-M is prefered.

- In the results, how can I distinguish NB-IoT cells from LTE-M cells ?

[Simon D-M]

Hi Vincent,

I'm sorry for the delay and the misunderstanding.

Vincent44 said:

Will I get the same results, no matter of XSYSTEMMODE ?

No, the function lte_lc_neighbor_cell_measurement(&params) is a wrapper that uses the AT command %NCELLMEAS. This AT command needs to have the modem enabled with +CFUN which depends on the %XSYSTEMMODE configuration.

Vincent44 said:

In the results, how can I distinguish NB-IoT cells from LTE-M cells ?

If you want to get both lists, I would recommend calling the function twice. Once allowing the modem only LTE-M and once with NB-IoT.

Best regards,

Simon Donnet-Monay