Interpolation Based Transmit Beamforming for MIMO-OFDM with Partial Feedback

Transmit beamforming with receive combining is a simple method for exploiting the significant diversity provided by multiple-input multiple-output (MIMO) systems, and the use of orthogonal frequency division multiplexing (OFDM) enables low complexity implementation of this scheme over frequency selective MIMO channels. Optimal beamforming requires channel state information in the form of the beamforming vectors corresponding to all the OFDM subcarriers. In an attempt to reduce the amount of feedback information, we propose a new approach to transmit beamforming that combines partial feedback and beamformer interpolation. In the proposed architecture, the receiver sends a fraction of information about optimal beamforming vectors to the transmitter, and the transmitter computes the beamforming vectors for all subcarriers through modified spherical linear interpolation of the conveyed beamforming vectors. Simulation results show that the proposed beamforming method requires much less feedback information than optimal beamforming while it exhibits slight diversity loss compared to the latter.