Precoding Design in MIMO Multiple-Access Cellular Relay Systems with Partial CSI

In this paper, we study the transmit precoding problem for multiple-input multiple-output (MIMO) multiple-access (MA) cellular systems employing cooperative base stations (BSs) and amplify-and-forward (AF) relaying where the antennas at the user equipments (UEs), relay terminals (RTs), and BSs are correlated. It is assumed that BSs have perfect channel state information (CSI) while user equipments (UEs) and RTs only have the channel covariance information (CCI). We derive the asymptotic sum-rate expressions for the MIMO-MA cellular systems for any given signaling input distributions in the large-system limit. Using the asymptotic results, we propose an efficient algorithm to determine the asymptotic optimum transmit matrices for the UEs and RTs that can maximize the sum-rate of the MIMO-MA cellular systems if CCI is exploited at the UEs and RTs.