LTE reconnection issue

[eguerard1]

Hello everyone,

I Have a LTE reconnection issue after LTE signal loss with SDK 1.3.6. I was doing some LTE connectivity tests by placing the board in a faraday box. After reopening the box the modem does not register back to network. (always cereg = 2). I've attached wireshark capture made with the cellular monitor tool. I also did the same test with SDK 2.5.2 and was not able to reproduce the problem.

Board: nRF9160DK

Modem firmware: 1.3.6

SDK: 2.6.1

Steps to reproduce:

1) Wait until the LTE is connected with the network

2) Close the faraday box and wait up to 1 minute

3) Open the box

Information on  the capture files:

Both capture files has been generated from reset and contains 1 connection loss action.

nRF9160_SDK2.6.1.pcapng

LTE connection loss at line 151 for around 1 minute

nrf9160_SDK2.5.2.pcapng

LTE connection loss at line 158 for around 1 minute

Can you help me to figure out why, in the case of SDK 2.6.1, is not able to reconnect to network at all ? Thanks for your help!

Eric

nRF9160_SDK2.6.1.pcapngnRF9160_SDK2.5.2.pcapng

[eguerard1]

Hi 0yvind,

To my knowkedge, we don't use any special settings. We are using BELL sim card. It is activated for LTE-M. We also use the PDN library in the device.

Best regards,

Eric

[eguerard1]

Hi 0yvind,

I finally found the problem. By doing your modem traces, I tried another SIM card manufacturer and found that the first time the device register on the network, it connects in LTE-M. When the device lost connection, it tries to reconnect in NB-IOT. The problem is NB-IOT is not widely support in Canada. The supported bearers changed from SDK 2.5.2 and version 2.6.2. I had to enforce to use the LTE-M bearer by adding these configuration options in the prj.conf.

CONFIG_LTE_NETWORK_MODE_LTE_M=y

CONFIG_LTE_NETWORK_MODE_LTE_M_NBIOT=n

 

I just want to thank you for the quick support you gave me!

Best regards,

Eric

[Øyvind]

Hi Eric, 

Happy to hear that you found the answer to your issue. Let us know if you have any further issues with the network connection. 

Kind regards,
Øyvind