On Joint Optimization of Source and Relay Precoding Design for MIMO Downlink Channels

This paper investigates the joint precoding optimization for a relay-assisted multi-antenna downlink system. Aiming at multiuser sum capacity maximization, we first propose an iterative optimization algorithm which exploits quadratic programming approaches. Inspired by the results obtained from the iterative optimization algorithm, in order to further reduce the computational complexity, we then develop an efficient source and relay precoding strategy which diagonalizes the compound channel of the backward and the forward channel in our system. Simulation results verify the effectiveness of our proposed precoding schemes.