Novel Adaptive Codebook-Based Limited Feedback Techniques for Multi-User MIMO-OFDM Systems

To mitigate the sum rate ceiling problems, high-resolution quantization and feedback schemes for the channel state information (CSI) are highly demanded in multi-user (MU) multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. In this paper, we investigate three adaptive codebook-based limited feedback techniques for MU-MIMO-OFDM broadcast systems. Using the channel covariance and mean respectively, adaptive codebook techniques I and II are extensions of two adaptive codebook techniques proposed for single-user MIMO single-carrier systems. Technique III is a totally novel proposal wherein both channel covariance and mean are exploited in the adaptive codebook construction. Numerical results show that the adaptive codebook approaches have significant sum rate gain compared to the fixed codebook solution and technique III outperforms techniques I and II.