This code package contains a simulation environment, based on Matlab, that reproduces the numerical results and figures in the paper

Ignacio Santamaria, Mohammad Soleymani, Eduard Jorswieck, and Jesus Gutierrez, "SNR Maximization in Beyond Diagonal RIS-assisted Single and Multiple Antenna Links", IEEE Signal Processing Letters 2023, vol. 30, pp. 923 - 926, 2023, DOI: 10.1109/LSP.2023.3296902

Abstract.- Reconfigurable intelligent surface (RIS) architectures not limited to diagonal phase shift matrices have recently been considered to increase their flexibility in shaping the wireless channel. One of these beyond-diagonal RIS or BD-RIS architectures leads to a unitary and symmetric RIS matrix. In this letter, we consider the problem of maximizing the signal-to-noise ratio (SNR) in single and multiple antenna links assisted by a BD-RIS. The Max-SNR problem admits a closed-form solution based on the Takagi factorization of a certain complex and symmetric matrix. This allows us to solve the max-SNR problem for SISO, SIMO, and MISO channels.

Acknowledgements: The work of Ignacio Santamaria was supported by the Ministerio de Ciencia e Innovación and AEI (10.13039/501100011033), under Grant PID2019-104958RBC43 (ADELE). The work of Eduard Jorswieck was supported by the Federal Ministry of Education and Research (BMBF, Germany) through the Program of Souverän. Digital. Vernetzt. joint Project 6G-RIC, under Grants 16KISK020K and 16KISK031

License and Referencing This code package is licensed under the GPLv2 license. If you in any way use this code for research that results in publications, please cite our original article listed above.