Joint MMSE transceiver design for multiuser non-regenerative MIMO relay downlink systems

This paper considers the multiuser non-regenerative MIMO relay systems in the context of the cellular downlink, where the base station simultaneously transmits data streams to multiple mobile stations through the relay station. All the nodes are equipped with multiple antennas. A joint transceiver design method is proposed to minimize the sum mean square error (MSE) of the system under the transmitted power constraints. Moreover, two special designs which the linear signal processing is performed at either the base station or relay station are studied, respectively. The closed-form expressions of the transceiver are obtained by using the Karush-Kuhn-Tucker (KKT) conditions and realized through an iterative algorithm with the guaranteed convergence, which provides a local optimal solution. Moreover, a greedy algorithm is developed to improve the performance by selecting a subset of mobile stations which have good channel conditions in each transmission. Simulation results compare different methods in terms of the average BER and the sum rate.