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,

It looks like the network rejects the connection. I need to check with our local FAE who will be back this tuesday to learn more about the situation.

Talk to your later.

Best regards,

Charlie

[Charlie]

Hi Luke,

Just want to confirm one thing. From the modem trace, I found the following information. According to LTE Release Causes - Telecompedia, it means Twilio network does not allow the device to connect. Can you confirm it isn't just a regular 4G sim card or others that do not give access to the NB-IoT network? I suppose you understand the difference, NB-IoT needs a specific sim card with a specific profile. There are not many things that can be done on the nrf9160 side. It also would be great if you can test with an NB-IoT sim card directly from T-mobile.

+CNEC_EMM: 11
....
+CNEC_EMM: 6
....

Cause #6 – Illegal ME

Cause #11 – PLMN not allowed

 

I am still waiting for the return of the local FAE.

Best regards,

Charlie

[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