BMA defines how many SACCH multiframes are used in measurement averaging in the BTS.The preprocessing of the measurement results in the BTS
reduces the traffic load of the LAPD links and BCSU units.
HYS defines the received RF power level hysteresis for required cell reselection.Higher the HYS ,less frequent will be cell reselection,and lesser the SDCCH usage for Location update.
*A little clarification, HYS is used for cells with different LACs only. That is this hysteresis is applied when reselection is to be made for cells of different LACs. (I thought someone might misunderstand it Bijoy)
Regarding BMA, I think it is used with some kind of feature “MR Preprocessing in BTS” etc. I am unaware of such feature in Ericsson. Please relief me Bijoy 🙂