Prefiltering in MIMO receiver

A radio receiver for demodulating data signals transmitted by a plurality of transmitting antennas over a radio channel, the receiver comprising control and communication circuitry configured to:

• receive, on a plurality of receiving antennas, at least a first data signal, a second data signal and a reference signal, the first data signal being received prior to the reference signal and the second data signal being received subsequent to the reference signal, the contents of the reference signal being known a priori to the receiver;
• calculate, using the contents of the reference signal, an estimated polynomial channel matrix;
• calculate, using the contents of the reference signal, a time-reversed estimated polynomial channel matrix;
• decompose the estimated polynomial channel matrix, the decomposing comprising a joint calculation of:
• a decomposition of the estimated polynomial channel matrix into a product of a first paraunitary polynomial matrix and a first upper triangular polynomial matrix with minimum-phase filters on its main diagonal, and
• a decomposition of the time-reversed estimated polynomial channel matrix into a product of a second paraunitary polynomial matrix and a second upper triangular polynomial matrix with said minimum-phase filters on its main diagonal;
• calculate a first polynomial pre-filter matrix as the paraconjugate of the first paraunitary polynomial matrix;
• calculate a second polynomial pre-filter matrix as the paraconjugate of the second paraunitary polynomial matrix;
• demodulate the received first data signal where the received first data signal is time-reversed and multiplied with the calculated second polynomial pre-filter matrix;
• and
• demodulate the received second data signal where the received second data signal is multiplied with the calculated first polynomial pre-filter matrix.

A non-transitory computer-readable medium comprising, stored thereupon, a computer program product comprising software instructions that, when executed in a processor in a radio receiver, cause the radio receiver to demodulate data signals transmitted by a plurality of transmitting antennas over a radio channel according to a process that comprises:

• receiving, on a plurality of receiving antennas, at least a first data signal, a second data signal and a reference signal, the first data signal being received prior to the reference signal and the second data signal being received subsequent to the 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, using the contents of the reference signal, a time-reversed estimated polynomial channel matrix;
• decomposing the estimated polynomial channel matrix, the decomposing comprising a joint calculation of:
• a decomposition of the estimated polynomial channel matrix into a product of a first paraunitary polynomial matrix and a first upper triangular polynomial matrix with minimum-phase filters on its main diagonal, and
• a decomposition of the time-reversed estimated polynomial channel matrix into a product of a second paraunitary polynomial matrix and a second upper triangular polynomial matrix with said minimum-phase filters on its main diagonal;
• calculating a first polynomial pre-filter matrix as the paraconjugate of the first paraunitary polynomial matrix;
• calculating a second polynomial pre-filter matrix as the paraconjugate of the second paraunitary polynomial matrix;
• demodulating the received first data signal where the received first data signal is time-reversed and multiplied with the calculated second polynomial pre-filter matrix;
• and
• demodulating the received second data signal where the received second data signal is multiplied with the calculated first polynomial pre-filter matrix.