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!

[Charlie]

Hi Luke,

Here are the comments from our local FAE.

Ibasis doesn't support NB.
I don't have a TMO SIM. We did pass certification on both LTE M and NB. That tells me NB is working.
It is unlikely the major mvno's support NB. I believe Vodafone supports NB. The MVNO's didn't think NB was mature enough for them to negotiate for.

Maybe you can reach Vodafone if you do need to use the NB-IoT network.

Best regards,

Charlie

[lbeckwit]

Hi Charlie,

Thanks for the information. I can confirm that the SIM I am using is specifically for NB (it is the NB-IoT sim from twilio discussed here).

I can look into getting a SIM directly from T-Mobile or Vodafone.

Just to confirm - it seems like on the Nordic side everything is fine (Nordic is certified for LTE and NB, the configuration I am using is correct), so the issue is potentially with Twilio?

Thanks,

Luke

[Charlie]

Yes, I can confirm the issue is potentially with Twilio. I hope you also tested on more than one nRF9160 device.

Best regards,

Charlie

[lbeckwit]

Hi Charlie,

I have been working with Twilio on this. They reached out to T-Mobile who said that supported boards should be on the list at the following site: https://wholesale.t-mobile.com/iot-solutions/modules-chipsets-devices. I was not able to find any Nordic boards/devices on that list.

Twilio said that if the board manufacturer (Nordic) has passed T-Mobile tested they need to request that T-Mobile add the device to that page in order for T-Mobile support to investigate the issue further.

Best,

Luke

[Charlie]

Hi Luke,

Thanks for your information. I talk with an expert who has been involved in Nordic chip T-Mobile certification. I confirmed that we are certified with T-mobile US, but they are slow to update their own pages, he will ping internally again so they can get nrf9160 onto their page. He also gives me some hints about your issue:

1) Except One note to be aware of is "⁴ T-Mobile US requires LwM2M carrier library for nRF9160 modem firmware version 1.3.1 and newer.", you should also make sure your device is using the B1 version of  nRF9160. nRF9160DK started to use B1 from v1.0.0, you can find the version mark from the chip surface.

2) Any chance to test with a sim card from T-Mobile directly?

Best regards,

Charlie