Testing both NB-IoT and LTE-M

RE: Testing both NB-IoT and LTE-M

Vincent44 — Mon, 24 Apr 2023 07:31:02 GMT

Hello,

I asked but did not get any response. It seems that the issue is due to the bad coverage in my area. At least, that's what has been suggested by Bouygues.

I have to say that I don't fully understand, since the iBasis SIM works perfectly fine in LTE-M. But it might be due to some agreements between service providers.
Anyway, I don't have much time to spend on this particular issue right now, so I will close this ticket. Thanks.

RE: Testing both NB-IoT and LTE-M

Didrik Rokhaug — Thu, 20 Apr 2023 11:48:13 GMT

Hello,

Did you manage to solve your problems?

Did you ask Bouygues what they require of LTE-M devices?

Best regards,

Didrik

RE: Testing both NB-IoT and LTE-M

Didrik Rokhaug — Tue, 11 Apr 2023 14:18:48 GMT

Hello again, and sorry for this taking a while, but Easter came in the way.

Do you know what Bouygues' M1 (LTE-M) subscription assumes (or could you ask them)? For example, what FGI bits must be set (in the UECapabilityInformation)? Do they expect the UE has IMS capability?

Best regards,

Didrik

RE: Testing both NB-IoT and LTE-M

Didrik Rokhaug — Fri, 31 Mar 2023 16:41:59 GMT

Does your application use UART1 (or SPI1 or TWI/I2C1)?

The trace from the at_client is fine, but the trace from your application seems to be missing parts, similar to your first trace.

You didn't set the system mode in the at_client trace (though that might have been bad instructions from me), but it starts by trying to connect to some LTE-M networks, before ending up connecting to an NB-IoT network in the end.

The first connection attempt (LTE-M) is to Bouygues Telecom. The connection attempt goes as expected until the network asks for the devices capabilities. After the device responds, the network stops communicating (it closes the RRC connection). However, it does not give a reject cause.

The device then tries to connect again a few times, both to the same cell, and to a different one (still Bouygues Telecom), but the same thing happens.

After a total of 6 connection attempts, it gives up, and tries to search for other networks. In the end, it tries to connect to Altice, but is rejected with "PLMN not allowed".

Next, it tries Orange, but is rejected with "EPS services not allowed in this PLMN".

Both of these rejects can probably be explained by missing roaming agreements between the operators.

It then switches over to NB-IoT, where it finds a cell from Bouygues Telecom, and this time it is able to connect.

I will have to ask the modem team why the network releases the device after it sends its capability information. However, due to Easter, it might take longer than normal to get a response.

In case you are interested, here is the communication between the device and the different networks: devzone.nordicsemi.com/.../trace-_2D00_-AT-Commands.pcapng

RE: Testing both NB-IoT and LTE-M

Vincent44 — Fri, 31 Mar 2023 10:06:19 GMT

Thanks Didrik.

Attached the test requested.

I also re-run a trace on my custom app, it might give some addition info ?

devzone.nordicsemi.com/.../trace-_2D00_-AT-Commands.bin devzone.nordicsemi.com/.../AT_2D00_log.txt devzone.nordicsemi.com/.../trace-_2D00_-My-App.bin

RE: Testing both NB-IoT and LTE-M

Didrik Rokhaug — Thu, 30 Mar 2023 15:45:51 GMT

[quote user="Vincent44"] Is trace supposed to be readable by non-Nordic people ?[/quote]

If you use the Trace Collector v2, you can convert the trace to a Wireshark .pcap. This will let you see the communication between the device and the network and server. It can even do this live, so you can see the communication happening in real-time.

However, there is more information that what Wireshark will show in the .bin files. That information is not readable for non-Nordic people though.

[quote user="Vincent44"] I hope I made this properly[/quote]

The trace seems a bit short, and I couldn't see any connection attempts from the modem. However, I do see some communication with a network, so there seems to be some information missing.

However, I can confirm that it did find a cell from Bouygues Telecom.

Could you try to take a new trace?

If you are using a DK, you can use this .hex file, which I have configured correctly: devzone.nordicsemi.com/.../72343.merged.hex

It is the at_client, so you will have to send the AT commands manually.

If you do use it, I am particularly interested in the output from these commands (they enable notifications from the modem, and will not give information directly):

AT+CEREG=5
AT%MDMEV=1
AT+CMEE=1
AT+CNEC=24
AT%CESQ=1

It would be nice if you could run those commands before you start the modem with AT+CFUN=1

RE: Testing both NB-IoT and LTE-M

Vincent44 — Wed, 29 Mar 2023 06:54:59 GMT

Attached the trace. I hope I made this properly. Is trace supposed to be readable by non-Nordic people ?

Operator is Bouygues Telecom (France), which provided me some test M2M SIM card.

Thanks.

devzone.nordicsemi.com/.../trace_2D00_2023_2D00_03_2D00_29T06_2D00_47_2D00_23.613Z.bin

RE: Testing both NB-IoT and LTE-M

Didrik Rokhaug — Tue, 28 Mar 2023 12:39:06 GMT

Hi,

Could you take a modem trace?

That will let us see what communication happens between the device and the network, which should give us an idea of why it cannot connect.

Also, what SIM card/operator are you using?

Best regards,

Didrik