Relay Power Minimization Approach Based on General-Rank Beamforming for Multi-Antenna Relaying Schemes

Cooperative multi-antenna transmission is considered in relay networks, in which a source transmits its information to destination with the help of multi-antenna relay. In the first phase, source transmits its signal to the multi-antenna relay. Then the relay manipulates the received signal with the general- rank complex beamforming matrix and retransmits it. Assuming second-order statistics of channel state information, general-rank complex beamforming matrix is determined to minimize the power that dissipated in the multi-antenna relay. We show that this approach yields a closed-form solution and dependency of the forward and backward channels can help us to improve the performance of the network up to 7 dB compared to independent channels.