LTE Link connecting is blocking?

RE: LTE Link connecting is blocking?

Simon — Wed, 13 Nov 2019 09:41:10 GMT

I got a reply:

"Delays in these new logs are caused by SIM Refresh.
In most logs only the third profile is able to register, first two got reject with cause #14 or #15.
It's up to the SIM card how quickly it will change the profile.

cause #14
IMSI: 901430000623824
Mobile Country Code (MCC): International Mobile, shared code (901)
Mobile Network Code (MNC): EMnify GmbH (43)

cause #15
IMSI: 206018874001895
Mobile Country Code (MCC): Belgium (206)
Mobile Network Code (MNC): Proximus (01)

OK
IMSI: 295050900053251
Mobile Country Code (MCC): Liechtenstein (295)
Mobile Network Code (MNC): Telecom Liechtenstein AG (05)"

Hopefully, this helped you.

Best regards,

Simon

RE: LTE Link connecting is blocking?

Simon — Tue, 12 Nov 2019 11:55:52 GMT

Thank you. I have provided the trace files internally and will report to you as soon as I get a reply.

Best regards,

Simon

RE: LTE Link connecting is blocking?

ExAg — Mon, 11 Nov 2019 13:23:35 GMT

Hi Simon

Here are some more trace files for you to analyse if you want. Today there was no single LTE connection attempt shorter than about 2 minutes. But I think you will see that in the trace files.

devzone.nordicsemi.com/.../Traces11_5F00_11_5F00_2019.zip

I had some difficulties to record the traces this time because the connection between the Trace Collector and the eval board or the connetion between the LTE link monitor and the eval board were lost relatively often. I have no idea why...

Best regards
Michael

RE: LTE Link connecting is blocking?

Simon — Fri, 08 Nov 2019 10:10:15 GMT

[quote user="Exelor AG"]Thank you for your answers. So its most likely an issue of our national telecom provider[/quote]

Yes, based on the trace you sent. If you sent more traces from other delays, we can confirm this with more certainty.

Best regards,

Simon

RE: LTE Link connecting is blocking?

ExAg — Thu, 07 Nov 2019 06:11:13 GMT

Hi Simon

Thank you for your answers. So its most likely an issue of our national telecom provider. I will discuss this with them. Because these long connection times have a big influence of the total power consumption of an battery powered IoT device out in the field.

The SIM card is specially for IoT purpose (for the M1 Network; NB is not yet supported at the moment).

Best regards
Michael

RE: LTE Link connecting is blocking?

Simon — Thu, 31 Oct 2019 11:53:14 GMT

Nothing is pointing to anything wrong on your side (nRF91), the network seems to have some capacity issues or other issues causing temporary registration failures.

However, without seeing additional logs from various delays we are not able to say anything for sure, there are always possibilities for errors in modem SW or maybe we can suggest workarounds for certain problems.

If you can provide more logs we can check those.

One thing I would suggest is to check with the operator that the SIM they are using is intended for IoT devices and is expected to work in the M1 network.

Best regards,

Simon

RE: LTE Link connecting is blocking?

ExAg — Wed, 30 Oct 2019 06:47:11 GMT

Hi Simon

Thank you for your reply. What exactly does this mean for us? I do not really understand, i am not an expert on LTE network connections. Are we doing something wrong?

The only thing I can say is that we are always using the same SIM for all our tests.

regards Michael

RE: LTE Link connecting is blocking?

Simon — Tue, 29 Oct 2019 09:53:32 GMT

I got the following reply:

"Without log from different delays not possible to say what is the reason in that case but sounds like failures are not always because of ESM cause #26.

If same SIM is always used then there is no difference in "NAS Signalling Low Priority", that is one factor defining UE behavior. If UE is configured for "NAS Signalling Low Priority" next attempt for ESM cause #26 will be done after 10 seconds.
Network can include backoff timer value in reject and in that case delay given by network is used.
With different EMM and ESM reject causes UE might be allowed to retry after 10 seconds."

RE: LTE Link connecting is blocking?

Simon — Mon, 28 Oct 2019 21:16:35 GMT

Sorry for the delay, I will ask internally tomorrow about this when I'm in office.

Best regards,

Simon

RE: LTE Link connecting is blocking?

ExAg — Thu, 24 Oct 2019 05:44:19 GMT

Hi Simon

Thank you for this analysis. So it's our national provider who has not enough capacity. But this changes from minute to minute...
The only thing strange are theese 12 minutes you mentioned, because the duration until the connection can be everything between some seconds, some minutes to over 10 minutes. It's not always fix 12 minutes.

Best regards and thank you again
Michael

RE: LTE Link connecting is blocking?

Simon — Wed, 23 Oct 2019 11:58:25 GMT

I got a reply. The reason for the long connection time is because the network rejects the Attach Procedure, due to cause #26 - insufficient resources (See 3GPP TS 24.301 Annex B, B.1). A timer with a timeout of 12 minutes is then started, and a new attempt to attach is done when the timer expires.

You should check with the operator if there is any plans to add more resources.

Best regards,

Simon

RE: LTE Link connecting is blocking?

Simon — Mon, 21 Oct 2019 13:02:54 GMT

Thank you. I have informed the ones responsible about the modem trace, and I will keep you updated when I get answers.

Best regards,

Simon

RE: LTE Link connecting is blocking?

ExAg — Mon, 21 Oct 2019 12:37:24 GMT

Hi Simon

I have attached the modem devzone.nordicsemi.com/.../trace_2D00_2019_2D00_10_2D00_21T12_2D00_15_2D00_37.075Z.bintrace file. It took several minutes to establish the LTE connection for this trace file.

Best regards
Michael

RE: LTE Link connecting is blocking?

Simon — Mon, 21 Oct 2019 09:37:25 GMT

I have reported your issue internally, and I am currently waiting for an answer. Could you provide a modem trace in the meantime?

Best regards,

Simon

RE: LTE Link connecting is blocking?

ExAg — Thu, 17 Oct 2019 09:24:40 GMT

Hi Simon

First it looked better after calling "lte_lc_power_off()" and power cycling the board. The connection was estalished several times in a row after only some seconds. But I allways had such phases with faster connection times.
After some intense testing, I thing it is the same as before. Sometimes it needs only 2s or 3s, but sometimes it nees over 5 minutes or even longer to establish the LTE connection.

Are the settings persistantly stored on the modem after "lte_lc_power_off()" or are they deleted after erasing the target and downloading a new intel HEX file? Or even when resetting the target an starting a new debug session?

Best regards
Michael

RE: LTE Link connecting is blocking?

Simon — Wed, 16 Oct 2019 12:04:00 GMT

[quote user="Exelor AG"]What exacltly do you mean with "AT+CFUN=0"? As I understand, it's the same as "lte_lc_power_off()", what causes a power off of the modem?[/quote]

I understand your confusion. I could not really find much documentation confirming that the modem settings are stored when calling this (except for a lot of devzone cases: here, here and here). In the nRF91 AT Commands documentation it says the following:

"When commanding the device to power off, wait for OK to make sure that Non-volatile Memory (NVM) has been updated."

In the NCS documentation it says the following:

"If the modem is shut down gracefully before the next boot (by using AT+CFUN=0), it keeps the current setting."

But, I will report it internally and ask for a more explicit explanation.

[quote user="Exelor AG"]Where in my code do I have to place this funtion call?[/quote]

Call it after a connection has been established. Try putting it right before while(1) loop, and remember to power cycle the device after this call has been made.

If you are still having problems after this has been done, please tell me and I will report that as well, and get somebody to consider your issue more carefully.

Best regards,

Simon

RE: LTE Link connecting is blocking?

ExAg — Tue, 15 Oct 2019 11:11:19 GMT

Hi Simon

Really strange behaviour. Today the first try to connect took over 3,5 Minutes. Than the 2. and 3. try only took ca. 3s to connect the LTE. So i do not think its bacauese I am "spaming" the network with connection tries.

What exacltly do you mean with "AT+CFUN=0"? As I understand, it's the same as "lte_lc_power_off()", what causes a power off of the modem?
How should this help with the connection time after starting a debug session?
Where in my code do I have to place this funtion call? I am using the Nordic MQTT TLS demo code:

void main(void)
{
  int err;

  if (!IS_ENABLED(CONFIG_AT_HOST_LIBRARY))
  {
    /* Stop the UART RX for power consumption reasons */
    NRF_UARTE0_NS->TASKS_STOPRX = 1;
    NRF_UARTE1_NS->TASKS_STOPRX = 1;
  }

  printk("The MQTT TLS simple sample started\n");
  
  provision_certificate();
  modem_configure();
  client_init(&client);
  err = mqtt_connect(&client);

  if (err != 0) 
  {
    printk("ERROR: mqtt_connect %d\n", err);
    return;
  }

  err = fds_init(&client);
  if (err != 0) 
  {
    printk("ERROR: fds_init %d\n", err);
    return;
  }

  while (1) 
  {
...
...
...

Best regards
Michael

RE: LTE Link connecting is blocking?

Simon — Thu, 10 Oct 2019 12:48:38 GMT

That should be sufficient.

However, a reason for this might be that the network detects that the same device tries to connects many times in a row in a given period of time. This may cause the network to block the device for a short period, to avoid it from flooding the base station.

I will try to get some feedback internally from people that knows more about this, and get it confirmed whether this is the reason, or if there is another reason.

You could also try to do some testing after calling AT+CFUN=0 followed by a modem reset. As mentioned earlier, this will store the network settings, and the connection time may decrease. Read more about it in this ticket.

Best regards,

Simon

RE: LTE Link connecting is blocking?

ExAg — Tue, 08 Oct 2019 06:16:25 GMT

Hi Simon

The signals strength is between -86dBm and -83dBm on my desk.

Regards
Michael

RE: LTE Link connecting is blocking?

ExAg — Mon, 07 Oct 2019 13:57:57 GMT

Hi Simon

I will check this thread.
I don't know the signal strength is, but it should always be the same because the dev-kit was on my table on the same position during all these tests.

Regards
Michael

RE: LTE Link connecting is blocking?

Simon — Wed, 02 Oct 2019 09:28:25 GMT

What is the signal strength when the connection establishment takes long time (7-9 minutes)? Check out this thread for more information about this and how to improve the performance.

Best regards,

Simon

RE: LTE Link connecting is blocking?

Simon — Mon, 23 Sep 2019 10:55:17 GMT

I am sorry for the delay, I have been sick lately, which is why I haven't been able to answer you. I will look into your issue the next couple of days.

Best regards,

Simon

RE: LTE Link connecting is blocking?

ExAg — Tue, 17 Sep 2019 07:30:26 GMT

Hi Simon

I just did some additional testing. I reloaded the mqtt_simple project (this one with TLS from GIT), clean and rebuild the project and downloaded the HEX onto the eval-kit.
My tests are without TLS enabled and without debugger (but it seems to have the same behaviour with the debugger now).
I used the reset button on the eval-kit to restart the application and measured the time between "LTE Link Connecting..." and "LTE Link Connected!".

I have the impression, that it is much better than it was; probably because of the new modem firmware 1.0.1.

Here are the results of 30 resets:

<5s:   25 times
20s:     1 time
1min:   1 time
>7min: 2 times
>9min: 1 time

best regards
ExAg

RE: LTE Link connecting is blocking?

ExAg — Mon, 16 Sep 2019 13:44:01 GMT

Hi Simon

No, I am not debugging on this low level of libraries (lte_lc.c). I see this behaviour on the line "modem_configure();" in main.c. (mqtt_simple or asset_tracker example does not matter).
If I single step over this line (or set a break point after this line), I see the text "LTE Link Connecting..." in the terminal. From now it takes 1:30 up to 6 minutes, until the text "LTE Link Connected!" appears in the terminal window and I am able to continue with single stepping.

I am using ncs_tag v1.0.0

No, I did not change the code. Its the original code provided by Nordic.

Regards
ExAg

RE: LTE Link connecting is blocking?

Simon — Mon, 16 Sep 2019 13:11:21 GMT

Just to make things clear. You are talking about the time between here and here?

I am not able to reprocuce your behaviour. What NCS tag are you using? Are you using the mqtt_simple example as it is or have you done any changes?

Best regards,

Simon