Method, comprising determining sizes of first and second data received at PCell for transmission to UE and of secondary parts of the first and second data transmitted from PCell to SCell for transmission to UE; deciding first and second initial times of the transmission of the respective data; deciding first and second primary final times indicating an end of transmission of the respective primary parts; monitoring an indication of a throughput of SCell; obtaining a transmission delay from PCell to SCell; estimating first and second secondary final times based on transmission delay, size of the respective secondary part, and the throughput; identifying first and second latest final times among the respective primary and secondary final times; calculating first and second throughputs of the transmission of the respective data based on the size of the respective data and a respective duration between the respective initial time and latest final time.