This repository contains code related to the following two papers:

SPAWC 24 paper

"MIMO capacity maximization with beyond-diagonal RIS," I. Santamaria, M. Soleymani, E. Jorswieck, and J. Gutierrez.

ICASSP 26 paper

"Riemannian optimization on the manifold of unitary and symmetric matrices with application to BD-RIS-assisted systems," I. Santamaria, M. Soleymani, E. Jorswieck, J. Gutierrez, and C. Beltran.

TSP manuscript (submitted)

"The manifold of unitary and symmetric matrices: Characterization, Riemannian optimization, and application to BD-RIS design," I. Santamaria, C. Beltran, E. Jorswieck, M. Soleymani and J. Gutierrez.

Content of Code Package

The code for each paper is in the corresponding folder. Both papers address the same problem: optimizing the (unitary and symmetric) BD-RIS to maximize capacity in a MIMO link. The low-rank version of Manifold Optimization (MO) algorithm with Phase Optimization (PO) presented in the TSP submission is significantly faster and is the one we recommend using. For comments or questions, please send an email to i.santamaria@unican.es

License and Referencing

This code package is licensed under the GNUv3 license. If you in any way use this code for research that results in publications, please cite our original article listed above.

Acknowledments

This work is supported by the European Commission’s Horizon Europe, Smart Networks and Services Joint Undertaking, research and innovation program under grant agreement 101139282, 6G-SENSES project. The work of I. Santamaria was also partly supported under grant PID2022-137099NB-C43 (MADDIE) funded by MCIN/AEI /10.13039/501100011033.