Hi Pix, you’ll be able to know the number of speech frames received by MS on a SACCH period only if Enhanced measurement Report are enabled on that cell. In fact the IE field NBR_RCVD_BLOCKS contains that information. The field DTX_USED instead informs BTS/BSC about the use of DTX in UL (on mS side) on the current SACCH perion. This information is fundamental for BTS: if DTX was sed by MS, BTS has to evaluate the SUB measurement set; if instead DTX was not used into the current SACCH period, BTS has to evaluate the FULL measurement set.
A remark: NBR_RCVD_BLOCKS is the number of correctly decoded speech frames on MS side. It can be < 24 also in case DTX was not used in DL, but there is interference on the DL link. BTS/BSC knows the right number of frames transmitted in DL, so it's able to perform the correct measurements. Regards, Michele