Precoder design of non-regenerative relays with covariance feedback

In this letter, the optimal form of the precoding matrix is initially derived to maximize the ergodic capacity between the source and destination with covariance information of the relay-destination link. The elements of the precoding matrix are then determined to maximize the upper bound of the ergodic capacity. The numerical results show that the performance of the proposed scheme is close to that of the full feedback scheme when there is a high correlation at the transmit antennas of the relay.