Lte link controller losing network coverage

[scjr_dev]

Hi,

I have several field devices using the LTE Link Controller library with nRF Connect SDK v2.5.1. Most of them work fine — they are programed to connect every hour. However, I’ve noticed 2 devices that were previously connecting fine suddenly lost connection because they were moved in an area with poor network coverage.

When these devices moved back into an area with good coverage, they never reconnected automatically. After performing a power cycle, they immediately reconnected and started working normally again.

Unfortunately, the only thing I was able to recover was a partial log which show the modem trying this every hour:

[27:01:28.516,723] <inf> app_event_manager: APP_EVT_DATA_GET - Requested data types (MOD_STAT)
[27:01:28.533,050] <err> modem_info_params: Link data not obtained: 5 -22
[27:01:28.533,081] <err> modem_module: modem_info_params_get, error: -22
[27:01:28.533,172] <inf> app_event_manager: MODEM_EVT_MODEM_STATIC_DATA_NOT_READY

I have two questions about the LTE Link Controller behavior:

1. Once lte_lc_connect_async() is called, does it need to be called again after a connection loss, or does the library automatically retry?

2. The CONFIG_LTE_NETWORK_TIMEOUT parameter is set to 600. From my understanding, it only applies during the initial lte_lc_connect_async() call. What happens after a connection loss — how many retries are attempted, and does the library eventually stop retrying at some point?

Thanks in advance for your help!

[dejans]

Hi,

When those 2 devices were moved to an area with poor connectivity, were they able to connect there automatically without problems but experienced problems when moved back to an area with good coverage?

Do you use PSM or eDRX in your application?

Which modem firmware version do you use?

Is there possibility that you obtain and send complete log?

Best regards,
Dejan

[scjr_dev]

Hi dejans,

dejans said:

When those 2 devices were moved to an area with poor connectivity, were they able to connect there automatically without problems but experienced problems when moved back to an area with good coverage?

They both lost connection. They both stop connecting completely and never reconnected again. I got to them and moved them back to a good coverage. They were not able to reconnect and I had to power cycle, which made them connect right away. 

dejans said:

Do you use PSM or eDRX in your application?

I use default asset tracker settings :

## Power saving timers.

### 320 hours PSM.

CONFIG_LTE_PSM_REQ=y

CONFIG_LTE_PROPRIETARY_PSM_REQ=y

CONFIG_LTE_PSM_REQ_RPTAU="10000001"

### 20 seconds active time.

CONFIG_LTE_PSM_REQ_RAT="00001010"

dejans said:

Which modem firmware version do you use?

2.0.2

dejans said:

Is there possibility that you obtain and send complete log?

Sorry I don't have more data cause I was not able to recaver logs on the field. When I moved them to a good coverage zone, I recorded the lines I sent already, before powere cycle them.

For now I am just looking to understand the LTE link library. Can you help answer my 2 questions?

Thanks