BSS pre-processing should be related to the averaging of basic radio measurements (rxlev(s), rxlev(n), rxqual, ta)
BSS decision algorithm should be related to HO algorithms & best candidate selection. Therefore it can be divided into 2 separate processes :
if rxlev(s) < xxx and rxqual > yyy then HO is detected
if 1/ is true, then the best candidate cell is the one that verify rxlev(n)>rxlev(s) + zzz and which belong to a certain layer type (micro, umbrella, etc)… etc.
3GPP does not provide any kind of mandatory algorithms for handover or candidate selection. Just guidelines, that one might or might not respect 🙂