Data signals transmitted by a plurality of transmitting antennas over a radio channel are demodulated. The method comprises receiving (202) on a plurality of receiving antennas, a first data signal, a reference signal and a second data signal, the contents of the reference signal being known a priori to the receiver. The contents of the reference signal are used for calculating (204) an estimated polynomial channel matrix and a time reversed version of the same. Polynomial pre-filter matrices are calculated (206, 208) by a decomposition of the estimated polynomial channel matrices into a respective product of a paraunitary polynomial matrix and an upper triangular polynomial matrix with minimum phase filters on its main diagonal, where the polynomial pre-filter matrices are obtained by calculating the paraconjugate of the paraunitary polynomial matrices. The received data signals are demodulated (212) where the received data signals are multiplied with the calculated polynomial pre-filter matrices.