Successive Transmit Beamforming Algorithms for Multiple-Antenna OFDM Systems

In this paper, we focus on the design and evaluation of new transmit beamforming algorithms for the multiple-input single-output (MISO) orthogonal frequency division multiplexing (OFDM) systems. The OFDM technique is very effective in combating frequency selective fading since it converts the broadband channel into several parallel flat fading channels. However, to implement transmit beamforming, the channel state information on each individual subcarrier has to be conveyed from the receiver to transmitter. In order to reduce the channel feedback requirement in the OFDM system, we take the time and frequency domain correlations of the channel fading into consideration. Based on our successive beamforming (SBF) technique, we develop several classes of feedback algorithms for the OFDM systems. These new algorithms use the knowledge from the previous frame or neighboring subcarrier to aid the beamforming codebook design for the current subcarrier. Through numerical simulations, we demonstrate that the proposed SBF algorithms require very little channel feedback, yet they provide better performance than that of the other existing OFDM beamformers