A first user terminal receives data during a time slot assigned for simultaneous transmission of data to a first set of at least one user terminal and to a second set of at least one user terminal using time-division multiplexing, estimates the applied power ratio between a first sub-channel to the first set and a second sub-channel to the second set (the available power ratios are divided into at least one known region and each applied power ratio belongs to one region), estimates bit error probability for each of the bursts of the received data; and applies an adaptation process in order to make the estimated bit error probabilities fall into one of bit error probability intervals of a predefined mapping table with a predetermined probability. which determines the bit error probability that is to be reported to a network.