Power allocation for the downlink of nonregenerative cooperative multi-user MIMO communication system

Amplify-and-forward (AF) is one of the most popular and simple approaches to transmit information over a cooperative multi-input multi-output (MIMO) relay channel. In this paper, we propose three novel power allocation methods for the downlink of cooperative multi-user MIMO AF system, which are designed to maximize the weighted sum-rate (WSR) of the cooperative system, by considering two different levels of channel state information (CSI). We design efficient precoding algorithms at the relay by assuming that either only the receive CSI or both receive and transmit CSI is available at the relay. Results show the performance improvement that our schemes can achieve in terms of sum-rate and WSR metrics.