there is no direct measurement, like BLER or PER, etc. So you have to look for an “effect” of BLER. And that’s going to be:
1/ the coding scheme used (CS1 CS2 CS3 CS4, MCS1 MCS2 MCS3…. MCS9)
–> problem : this usage is also impacted by your system congestion, so it’s not clear-cut whether there is congestion when the MCS is bad.
2/ the rate of retransmission –> this one is much more useful