Energy-Efficient MIMO Communication Assisted by Metasurfaces with Global Reflection Constraints

This paper investigates the design of a MIMO communication system enhanced by a reconfigurable holographic surface (RHS) positioned near the transmitter. The system is optimized through the joint design of the transmit covariance matrix and the RHS reflection coefficients. The RHS is configured using sequential fractional programming, while two strategies are explored for optimizing the transmit covariance matrix: one based on fractional programming, and the other involving a search over a standard-compliant codebook. A performance comparison between the two methods demonstrates that the codebook-based approach achieves results close to those of the more computationally intensive fractional programming method. Both passive and active RHS implementations-where the latter includes analog amplification-are considered, providing a comprehensive analysis of system performance under varying hardware capabilities.