On the spectral efficiency maximization of nonregenerative cooperative MIMO communication systems

Amplify-and-forward (AF) is one of the most common and simple approaches for transmitting information over a cooperative multi-input multi-output (MIMO) relay channel. It has recently been demonstrated that the spectral efficiency of AF scheme can be maximized by using the relay as a smart precoder. However, source node precoding has not been included in the overall maximization problem. In this paper, we propose a joint precoder design at the relay and source nodes for maximizing the cooperative mutual information (MI), i.e., the combination of direct and relay link MI, and thus, for further improving the spectral efficiency of AF scheme. In addition, we provide an algorithm for performing our joint precoding technique. Performance analysis indicates that our novel precoding algorithm outperforms other existing AF precoding methods in various link configurations.