A Limited Feedback Precoder Method for OFDM Relay Systems

Based on OFDM amplify-and-forward cooperative relay system, in order to reduce the transmission bit error rate, while increasing the channel capacity and improving the usability, the paper presents a practical limited bits feedback precoding method where the source node precoder and the relay node precoder are jointly optimized. Through the use of the two downlink with three nodes, the two-hop cooperative communications are achieved, and the precoding matrices are designed using both orthogonal triangular (QR) decomposition and Singular Value Decomposition (SVD), in which the source node precoder contains only one precoding matrix per OFDM frame. By choosing a better codebook, the quantization precoders are feedbacked to the transmitter. The simulation results indicate that the proposed method is able to improve the system average sum-rate, reduce the error rate and improve the performance of outage probability, indicating a chance of better usability as result of fewer bits.