Energy Efficiency Maximization of MIMO Systems through Reconfigurable Holographic Beamforming

This study considers a point-to-point wireless link, in which both the transmitter and receiver are equipped with multiple antennas. In addition, two nearly-passive reconfigurable metasurfaces are deployed, one in the immediate vicinity of the transmitter, and one in the immediate vicinity of the receiver. In this scenario, the system energy efficiency is optimized with respect to the transmit covariance matrix, and the reflection matrices of the two metasurfaces. A low-complexity algorithm is developed, which is converges to a first-order optimal point of the maximization problem.Moreover, closed-form expressions are derived for the metasurface matrices in the special case of single-antenna or single-stream transmission. A numerical performance analysis shows, in particular, that the considered architecture can provide significant energy efficiency gains compared to fully digital beamforming architectures.