LTE Link connecting is blocking?

[ExAg]

Hi

In the mqtt_simple example there is a line "modem_configure();" which establishes the LTE Link connection. If connecting the LTE link is not possible (for example no signal), this function never returns.

1. Is this the intention of this function or is there a possibility to configure a timeout?

2. Is it normal, that this function needs several minutes to establish the LTE link, if a provider is present?

regards

ExAg

[Simon]

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

[ExAg]

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

[ExAg]

Hi Simon

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

Regards
Michael

[Simon]

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

[ExAg]

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