Relay beamforming design with SIC detection for MIMO multi-relay networks with imperfect CSI

Abstract—In this paper, we consider a dual-hop multiple-input– multiple-output (MIMO) wireless multirelay network, in which a source–destination pair, both equipped with multiple antennas, communicates through multiple half-duplex amplify-and-forward (AF) relay terminals, which are also with multiple antennas. Since perfect channel-state information (CSI) is difficult to obtain in a practical multirelay network, we consider imperfect CSI for all channels. We focus on maximizing the signal-to-interference-plus-noise ratio (SINR) at the destination. We propose a novel robust linear beamforming at the relays, based on the QR decom-position filter at the destination node, which performs successive interference cancellation (SIC). Using the law of large numbers, we obtain the asymptotic rate in the presence of imperfect CSI, upon which the proposed relay beamforming is optimized. Simula-tion results show that the asymptotic rate matches with the ergodic rate well. Analysis and simulation results demonstrate that the proposed beamforming outperforms the conventional beamform-ing schemes for any power of CSI errors and SNR regions. Index Terms—Channel state information (CSI), multiple-input– multiple-output (MIMO) relay, rate, relay beamforming, succes-sive interference cancellation (SIC) detection. I