Joint time-frequency beamforming for MIMO-OFDM systems

In this paper, we presented a joint time-frequency beamforming scheme for an OFDM system with MIMO antennas, where both frequency-domain and time-domain beamforming are employed. Using the proposed scheme, better performance can be achieved by using more DFT/IDFT blocks at the receiver and/or the transmitter. However, the margin of the performance improvement decreases along with the increase of the number of DFT/IDFT blocks. Therefore, the proposed scheme can be used to effectively trade off system performance and complexity. Furthermore, to calculate the weighting coefficients for the proposed scheme, we propose an iterative algorithm to achieve good performance with reasonable complexity.