You meaning the table in 45.008 (AnnexD)? I think, it is only for example. In our RAN the triggering of the switch does not use separate measurements of channel quality, but
it is executed by analyzing the number of blocks to be repeated (not acknowledged
blocks) versus the number of transmitted blocks in total. Link adaptation is then
based on BLER measurements (indirect measures of the radio quality). They are really fixed in BSC database and stored in pre-calculated matrix tables, one for each possible RF environment, since switching points depend on the actual RF scenario (lowDiversity or highDiversity). These switching points are varied for different transitions MCSi->MCSj, different RF scenario, and whether the incremental redundancy (IR)used or not.