Two Novel Interpolation Algorithms for MIMO-OFDM Systems with Limited Feedback

Transmit beamforming and receive combining, which is used in multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems, is investigated in this paper. The complexity of linear spherical interpolation algorithm is too large and it can only be applied to unquantized beamforming, so we propose a general spherical interpolation method. This method feeds back pilot subcarrier beamforming vectors to the transmitter, then using the channel correlation in frequency domain, the beamforming vectors for non-pilot subcarriers are reconstructed according to that of the two neighboring pilot subcarriers using the general spherical interpolation algorithm. Simulation results show that this algorithm is applicable not only for unquantized beamforming, but also for quantized beamforming. Considering the realization of the actual system, we propose a phase quantized method. Simulations demonstrate that the performance of the phase quantization method outperforms existing MIMO-OFDM beamforming interpolation algorithms, and is easy to realize in actual system.