Reliable RF beamforming for millimeter wave MIMO-OFDM systems

In this paper, we propose a novel spatial diversity scheme for the radio-frequency (RF) beamforming in millimeter wave (mmWave) MIMO-OFDM systems under the assumption of partial channel knowledge at the transmitter and full channel knowledge at the receiver. We formulate the spatial diversity problem as maximizing the geometric mean of the projections of the RF precoder on the transmit steering vectors and the geometric mean of the projections of the RF combiner on the receive steering vectors. To solve the optimization problem of the RF beamformers, we propose a simple gradient ascent algorithm. Simulation results show that our proposed spatial diversity scheme outperforms the other spatial diversity schemes in literature in case of no blockage and in case of blockage to any propagation path regardless of the number of propagation paths.