Iterative Joint Source and Relay Optimization for Multiuser MIMO Relay Systems

In this paper, a joint source and relay optimization problem is studied for a multiuser multiple-input multiple-output (MIMO) relay system. Assuming that the channel state information (CSI) at the source and relay is available, two amplify and forward (AF) relaying schemes are proposed under the criterion of maximizing the sum-rate. First, a scheme which iteratively searches the optimal source and relay matrices by deriving the partial derivatives of the sum-rate and applying the gradient search algorithm is proposed. Next, in order to reduce the computational complexity, an alternating method utilizing the equivalent channel method is developed. This method also resorts to a so called maximum-signal-leakage-and-noise-ratio (SLNR) that can suppress the co-channel interference (CCI) and noise at the users effectively. Theoretical analysis and Monte Carlo simulation illustrate the performance of the both schemes.