Hi, I've noticed a strange behavior of my device. I'm using a nRF9160-based custom board with nCS v2.6.0 and modem version 1.3.6.
Long story short - after trying to acquire a GPS fix, the device fails to perform neighbor cell measurements.
Short story long - the scenario is as follows:
- The device connects to the LTE network.
- The device performs
lte_lc_neighbor_cell_measurementand successfully acquires the neighbor cell measurements. - The device do some stuff and disconnects from the network.
- The device sleeps for some time.
The logs are as follows:[22:32:08.016,662] <inf> connectivity: LTE connection order taken+CEREG: 2, <hidden data>[22:32:09.131,622] <inf> connectivity: Searching for network+CSCON: 1+CEREG: 5, <hidden data>[22:32:10.219,573] <inf> connectivity: Connected to: roaming network%NCELLMEAS: 0, <hidden data>[22:32:10.222,320] <inf> connectivity: RSRP: -86, RSRQ: -12%XTIME: <hidden data>+CSCON: 0+CSCON: 1
We see that the %NCELLMEAS: 0 message with proper data is received, which means that the neighbor cell measurements were successfully acquired. It happens after the device connects to the network.
After the operations described above have been performed a few times (always with success), we want to acquire the GPS fix:
- The device connects to the LTE network.
- The device tries to acquire the GPS fix using
location_requestusingLOCATION_METHOD_GNSS, LOCATION_METHOD_CELLULARmethods and successfully acquires the fix. - The device tries to perform
lte_lc_neighbor_cell_measurementand fails. - The device disconnects from the network.
- The device sleeps for some time.
After acquiring the GPS fix, each try to receive the neighbor cell measurements fails in the following way:
[28:32:08.016,662] <inf> connectivity: LTE connection order taken%NCELLMEAS: 1[28:32:08.410,827] <inf> connectivity: RSRP: -140, RSRQ: -20+CEREG: 2, <hidden data>[28:32:09.135,833] <inf> connectivity: Searching for network+CSCON: 1+CEREG: 5, <hidden data>[28:32:09.984,832] <inf> connectivity: Connected to: roaming network%XTIME: <hidden data>+CSCON: 0+CSCON: 1
We see that the %NCELLMEAS: 1 message with no data is received (logs shows always RSRP: -140, RSRQ: -20 because of our calculations in the code, but the callback returns "invalid values") at the very beginning of the LTE connection, which means that the neighbor cell measurements were not acquired, even though we didn't call lte_lc_neighbor_cell_measurement yet.
After that, the device performs the lte_lc_neighbor_cell_measurement and fails almost all the time. There is a slight chance that maybe 1/10 times the measurements are acquired successfully. After rebooting the device, everything works fine again until the GPS fix is acquired.
Can you try to reproduce the issue on your side? Do you have any idea what could be the reason for this behavior?
Thanks in advance for your help.