A limited-feedback-based optimal precoding algorithm for OFDM multi-relay networks

Based on amplify-and-forward cooperative relay under frequency selective fading channels, in order to reduce the feedback load of OFDM-based wireless systems, a practical limited bits feedback precoding algorithm is proposed. Using matrix decomposition method, precoding matrices are designed. The source node precoding need only one precoding matrix per OFDM frame. Source precoder and relay precoder are jointly optimized and quantified. The precoding matrix index is fed back for Clustered subcarrier of OFDM. The algorithm achieves precoding matrices at source and relay nodes with limited feedback. Simulations indicate that the proposed method can improve bit-error-rate performance. The bit error rates are also compared with different relay number.