MIMO Capacity Maximization with Beyond-Diagonal RIS
<|reference_start|>MIMO Capacity Maximization with Beyond-Diagonal RIS: This paper addresses the problem of maximizing the capacity of a multiple-input multiple-output (MIMO) link assisted by a beyond-diagonal reconfigurable intelligent surface (BD-RIS). We maximize the capacity by alternately optimizing the transmit covariance matrix, and the BD-RIS scattering matrix, which, according to network theory, should be unitary and symmetric. These constraints make the optimization of BD-RIS more challenging than that of diagonal RIS. To find a stationary point of the capacity we maximize a sequence of quadratic problems in the manifold of unitary matrices. This leads to an efficient algorithm that always improves the capacity obtained by a diagonal RIS. Through simulation examples, we study the capacity improvement provided by a passive BD-RIS architecture over the conventional RIS model in which the phase shift matrix is diagonal.<|reference_end|>
@article{santamaria2024mimo,
    title={MIMO Capacity Maximization with Beyond-Diagonal RIS},
    author={Ignacio Santamaria, Mohammad Soleymani, Eduard Jorswieck, Jes'us
  Guti'errez},
    journal={arXiv preprint arXiv:2406.02170},
    year={2024},
    archivePrefix={arXiv},
    eprint={2406.02170},
    primaryClass={cs.IT eess.SP math.IT}
}