Throughput-Maximizing Limited Feedback for Transmit Beamforming in MISO-OFDM Systems

In this paper, a new throughput-maximizing transmit beamforming scheme with limited feedback is presented in Multiple-Input Single-Output Orthogonal Frequency Division Multiplexing (MISO-OFDM) systems. By dividing the total subcarriers of an OFDM symbol into a series of clusters, from the codebook the proper codeword maximizing the average throughput per subcarrier of the considered cluster is chosen as the BeamForming Vector (BFV) for this one. In low Signal to Noise Ratio (SNR) range, the close-form expression of the optimal BFV is derived. While in high SNR range, since the close-form expression of the optimal BFV is difficult to found, a simple sub-optimal algorithm exploiting the correlation of channel frequency responses at different subcarriers is proposed to reduce the computational complexity of the exhaustive search in the optimal solution. The simulation results show that the proposed algorithm can provide not only higher throughput but also lower bit error rate than other existing schemes.