Coordinated beamforming for MIMO interference relay channel with multiple stream transmission

In this paper, we propose a precoding algorithm called flexible coordinated beamforming for the MIMO interference relay channel (IRC-FlexCoBF), where two base stations equipped with multiple antennas transmit to two user terminals simultaneously with the assistance of an amplify-and-forward relay that also has multiple antennas. The case of multiple data stream transmission is considered. The relay amplification matrix is predetermined so that the interference relay channel is converted to the conventional interference channel. Then two precoders supporting multiple stream transmission in the interference channel are applied and compared. Simulation results show that the IRC-FlexCoBF algorithm achieves a higher sum rate than the stream control method. Furthermore, a higher robustness of the IRC-FlexCoBF algorithm to inter-user interference is demonstrated. Finally, the gain in sum rate confirms the advantage of cooperatively sharing a relay compared to the case where the relay is accessed exclusively by two transceiver pairs operating in a time-division-multiple-access (TDMA) mode.