A method in a radio receiver for demodulating data signals transmitted by a plurality of transmitting antennas over a radio channel, the method comprising: - receiving on a plurality of receiving antennas, a data signal and a reference signal, the contents of the reference signal being known a priori to the receiver, - calculating, using the contents of the reference signal, an estimated polynomial channel matrix, - calculating a decomposition of the estimated polynomial channel matrix into a product of a paraunitary polynomial matrix and an upper triangular polynomial matrix, - calculating a polynomial pre-filter matrix as the paraconjugate of the paraunitary polynomial matrix, and - demodulating the received data signal where the received data signal is multiplied with the calculated polynomial pre-filter matrix, and wherein the method is characterized in that: - the upper triangular polynomial matrix has minimum phase filters on its main diagonal; and in that: - the calculation of the decomposition comprises: - assigning, to the first column of the paraunitary polynomial matrix, a normalized version of the first column of the estimated polynomial channel matrix, and for each current column from a second column to a last column of the channel matrix: - calculating projections of the current column of the estimated polynomial channel matrix on the previous columns of the paraunitary polynomial matrix, - calculating a difference polynomial vector as the difference between the current column of the estimated polynomial channel matrix and a product of the calculated projections multiplied by the previous columns of the paraunitary polynomial matrix, and - assigning, to the current column of the paraunitary polynomial matrix, a normalized version of the calculated difference polynomial vector. - receiving on a plurality of receiving antennas, a data signal and a reference signal, the contents of the reference signal being known a priori to the receiver, - calculating, using the contents of the reference signal, an estimated polynomial channel matrix, - calculating a decomposition of the estimated polynomial channel matrix into a product of a paraunitary polynomial matrix and an upper triangular polynomial matrix, - calculating a polynomial pre-filter matrix as the paraconjugate of the paraunitary polynomial matrix, and - demodulating the received data signal where the received data signal is multiplied with the calculated polynomial pre-filter matrix, and wherein the method is characterized in that: - the upper triangular polynomial matrix has minimum phase filters on its main diagonal; and in that: - the calculation of the decomposition comprises: - assigning, to the first column of the paraunitary polynomial matrix, a normalized version of the first column of the estimated polynomial channel matrix, and for each current column from a second column to a last column of the channel matrix: - calculating projections of the current column of the estimated polynomial channel matrix on the previous columns of the paraunitary polynomial matrix, - calculating a difference polynomial vector as the difference between the current column of the estimated polynomial channel matrix and a product of the calculated projections multiplied by the previous columns of the paraunitary polynomial matrix, and - assigning, to the current column of the paraunitary polynomial matrix, a normalized version of the calculated difference polynomial vector. - assigning, to the first column of the paraunitary polynomial matrix, a normalized version of the first column of the estimated polynomial channel matrix, and for each current column from a second column to a last column of the channel matrix: - calculating projections of the current column of the estimated polynomial channel matrix on the previous columns of the paraunitary polynomial matrix, - calculating a difference polynomial vector as the difference between the current column of the estimated polynomial channel matrix and a product of the calculated projections multiplied by the previous columns of the paraunitary polynomial matrix, and - assigning, to the current column of the paraunitary polynomial matrix, a normalized version of the calculated difference polynomial vector.