{"ID":2881842,"CreatedAt":"2026-06-01T04:54:23.091178241Z","UpdatedAt":"2026-06-01T04:54:23.091178241Z","DeletedAt":null,"paper_url":"https://arxiv.org/abs/2508.11292","arxiv_id":"2508.11292","title":"Beyond Diagonal Reconfigurable Intelligent Surface Enabled Sensing: Cramer-Rao Bound Optimization","abstract":"Recently, beyond diagonal reconfigurable intelligent surface (BD-RIS) has emerged as a more flexible solution to engineer the wireless propagation channels, thanks to its non-diagonal reflecting matrix. Although the gain of the BD-RIS over the conventional RIS in communication has been revealed in many works, its gain in 6G sensing is still unknown. This motivates us to study the BD-RIS assisted sensing in this letter. Specifically, we derive the Cramer-Rao bound (CRB) for estimating the angle-of-arrival (AOA) from the target to the BD-RIS under the constraint that the BD-RIS scattering matrix is unitary. To minimize the CRB, we develop an optimization scheme based on an adaptive Riemannian steepest ascent algorithm that can satisfy the non-convex unitary constraint. Numerical results demonstrate that the proposed BD-RIS-assisted target localization method achieves superior sensing performance.","short_abstract":"Recently, beyond diagonal reconfigurable intelligent surface (BD-RIS) has emerged as a more flexible solution to engineer the wireless propagation channels, thanks to its non-diagonal reflecting matrix. Although the gain of the BD-RIS over the conventional RIS in communication has been revealed in many works, its gain...","url_abs":"https://arxiv.org/abs/2508.11292","url_pdf":"https://arxiv.org/pdf/2508.11292v1","authors":"[\"Xiaoqi Zhang\",\"Liang Liu\",\"Shuowen Zhang\",\"Haijun Zhang\"]","published":"2025-08-15T07:55:23Z","proceeding":"eess.SP","tasks":"[\"eess.SP\",\"cs.IT\"]","methods":"[]","has_code":false}