Efficient Linear Transmission Strategy for MIMO Relaying Broadcast Channels with Direct Links

In this letter, a novel linear transmission strategy to design the linear precoding matrix (PM) at base station (BS) and the beamforming matrix (BM) at relay station (RS) for multiple-input multiple-output (MIMO) relaying broadcast channels with direct channel (DC) is proposed, in which a linear PM is designed at BS based on DC, and the RS utilizes the PM, the backward channel and the forward channel to design the linear BM. We then give a quite tight lower bound of the achievable sum-rate of the network with the proposed strategy to measure the performance. The sum-rates achieved by the proposed strategy is compared with other schemes without considering the DC in design in simulations, which shows that the proposed strategy outperforms the existing methods when RS is close to BS.