Analog feedback for MIMO-OFDM systems

This paper addresses the analog feedback of channel state information (CSI) in multiple-input-multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) based wideband wireless communication systems. In MIMO-OFDM systems, the amount of CSI to be fed back grows prohibitively with the number of subcarriers. Aiming at reducing the feedback overhead, we design efficient analog feedback schemes. In our approach, the user equipment (UE) samples the CSI so that only a small fraction of the CSI needs to be fed back to the base station (BS). Based on the sampled feedback information, the BS reconstructs full CSI using some interpolation method. Low complexity clustering/interpolation based schemes are first considered, but these schemes only provide limited feedback quality. To improve the performance, we analyze the sparsity of the time-domain channel impulse response and propose a time-domain filtering scheme based on the sparsity property. Simulation results show that the time-domain filtering scheme efficiently decreases the interpolation distortion and feedback error, and achieves much better performance than the clustering/interpolation based schemes.