Comparative study of transmit weight designs for nonregenerative Multiuser MIMO downlink relay system

In this paper, we focus on the cancellation of the interferences among Destination Users (DU´s) in the nonregenerative Multiuser Multiple-Input Multiple-Output (MU-MIMO) downlink relay system. By the comparison with Block Diagonalization (BD) and conventional Dirty Paper Coding (DPC) based on LQ Decomposition(LQD), a novel design method of transmit weights for DPC is proposed to successively eliminate the interference among DU´s, each of which is equipped with multiple receive antennas. For the proposed schemes, we firstly study the transmit weights design for the conventional Amplify-and-Forward (AF) relay system where the Relay Station (RS) just retransmits the amplified received signals, then we extend it to the joint design of transmit weights both at the Base Station (BS) and the RS, where a DU selection algorithm with low complexity is adopted at the RS to obtain the multiuser diversity. The comparisons of rate performances and BER characteristics between the proposed schemes and the conventional methods verify the effectiveness of the proposed schemes.