Power control and beamformer design for the optimization of full-duplex MIMO relays in a dual-hop MISO link

This paper studies the optimization of a dual-hop multi-input single-output (MISO) link with a full-duplex multi-input multi-output (MIMO) relay connecting the end nodes based on the amplify-and-forward or decode-and-forward protocol. The direct end-to-end link is considered weak, hence interpreted as interference by the dual-hop relay link. We observe a duality between the first and second hops in terms of transmit powers, and show that one of them always optimally converges to its upper bound. In addition, we combine the minimum mean square error-based receive beamformer with the optimal transmit powers as an iterative approach is not guaranteed to converge to global optimum. Moreover, we introduce a new figure of merit to approximate the optimal transmit beamformers, which is based on the maximization of the signal-to-leakage-plus-noise ratio, and present an iterative algorithm to jointly optimize the receive and transmit beamformers as well as the transmit powers. The numerical results demonstrate that the joint iterative algorithm can achieve higher data rates with the leakage-based transmit beamformers than those with conventional transmit filtering.