nrf9160 %NCELLMEAS requirements


When using the NCELLMEAS (search_type = 3) command I get inconsistent results. Generally, I don't see more than 1 neighbor. If my device (nRF9160, mfw 1.3.2) is in my basement I do get 1 neighbor in 2 out of 3 measurements, in my backyard I get none.

What requirements do need to be met so that NCELLMEAS returns all neighboring cells?

After going through some posts (specifically this one with a similar issue:  RE: nrf9160 AT%NCELLMEAS reports only 1 cell ) I understand that there are multiple variables that affect the output:

  1. Only LTE-M/NB-IoT cells are detected
  2. Results depend on the network configuration:
    1. SIB3 is minimum requirement for neighbor cell measurements. SIB4 includes additional information about intra neighbor but not mandatory for intra measurements. SIB5 (in addition to SIB3) is required for inter measurements. Otherwise results are available only from own cell.
    2. NCELLMEAS issued while UE is in RRC connected mode is not (always?) configured. Results are available only from own cell if not configured.

Is this correct?

I couldn't find much of a documentation on this. If someone can point me to a source where I can read up on this that would be much appreciated.