Cannot connect to T-Mobile NB-IoT on NRF9160

[lbeckwit]

Hello!

I have been trying to connect to T-Mobile's NB-IoT network using a NRF9160DK with a Twilio Narrowband sim, but have been unsuccessful so far. I have been able to successfully run applications on LTE connections using both a Twilio sim on T-Mobile's network as well as with an iBasis sim, but when I switch to NB-IoT it does not work properly. I am located in northern VA near DC and T-Mobile does have NB-IoT coverage here.

I was looking over past threads and found this one: https://devzone.nordicsemi.com/f/nordic-q-a/61681/nrf9160-doesn-t-connect-over-nb-iot-ibasis-and-t-mobile-works-fine-on-cat-m, which seems to conclude that T-Mobile does not allow Nordic boards to connect to their network. However that was 2 years ago.

Does anyone know if T-Mobile allows Nordic boards to connect to their NB-IoT network, and if not are there any other services in the US that work for NB-IoT?

Thanks!

[Burt]

I am trying to connect to T-Mobile using the "Twilio and T-Mobile present Narrowband" SIM card. It is a no go. I tried adding the LWM2M Carrier Library to my asset_tracker_v2, but that was just useless code bloat (requiring me to make use of the external flash on my custom nRF9160 card). My reading of your documents suggests that there is no need to add that library to my code image, so I guess it is not surprising it was no help. I am adding to a ticket that was opened two years ago, so hopefully in that time you have worked with Twilio to come up with a usable procedure. Soracom SIMs work fine for T-Mobile NB-IoT, but we have some Twilio SIMs designed specifically for T-Mobile NB-IoT except that they don't work for me. Please help. Thanks.

Burt Silverman

ps if it could be solved by adding the LWM2M carrier library, then what information has to be programmed? I tried using the LWM2M Carrier Shell but one thing is that it seemed to only know about LTE-M rather than NB-IoT. Also, any attempts to make a custom setting seemed to disappear when I replaced the Carrier Shell application with asset_tracker_v2. Thanks, again.

[Charlie]

Hi Burt,

Any chance to test with an T-Mobile SIM card? As you know, T-Mobile is the final local network service provider. If the device works with both T-Mobile and Soracom SIMs using NB-IoT network, I did not see the reason why "Twilio and T-Mobile present Narrowband" SIM card does not work if it has no problem, because nRF9160 device are standard LTE-M/NB-IoT compliance device, and it has pass certification requirement with local network operator in most regions, so we do not need talk with every network operator(especially MVNO) to make sure the device works with their network. 

If you still want to use "Twilio and T-Mobile present Narrowband" SIM card, check with Twilio first in case they already notified this issue, and I will provide any assistant we can offer to help. 

Best regards,

Charlie

[Burt]

Thank you, Charlie. I have opened a ticket with Twilio. Something strange is going on in the business end of things. Twilio has become part of Kore Wireless. I discovered it is not possible to purchase new NB-IoT SIMs, but only their Super SIMs which only work on LTE-M. Whereas they once provided an NB-IoT starter developer's kit, T-Mobile no longer does. Or maybe it was Twilio that provided the kit--in any case, it is no longer available. On GitHub it looks like Twilio hasn't done anything in five years. I will open a ticket with T-Mobile and ask if they are providing SIMs for their network. It may be time to toss the Twilio SIMs in the garbage can and stick with the Soracom SIMs.

Burt