The invention relates to a signal processing method which optimizes the bit error rate under pragmatic conditions. The signalling method is optimally matched to the radio channel, variable with time, in rapid sequence by means of linear operations. Uplink and downlink transmission sides are determined by an excess of antennae on the downlink transmission side. The estimations of the channel matrix in the one transmission direction, necessary for the matching of the transmitter, can, in the absence of common-channel distortions with the condition of channel reciprocity, be directly obtained from the estimations for the other transmission direction. By a suitable linear combination of the transmission signals and, optionally, also the received signals, an error-free bi-directional transmission of data streams can be achieved in Rayleigh and Rice channels with significantly lower transmission powers than in purely receiver-side linear signal processing.