Survey on Beyond Diagonal RIS Enabled 6G Wireless Networks: Fundamentals, Recent Advances, and Challenges

Wali Ullah Khan; Manzoor Ahmed; Chandan Kumar Sheemar; Marco Di Renzo; Eva Lagunas; Asad Mahmood; Syed Tariq Shah; Octavia A. Dobre; Jorge Querol; Symeon Chatzinotas

arXiv · 2503.08423

Survey on Beyond Diagonal RIS Enabled 6G Wireless Networks: Fundamentals, Recent Advances, and Challenges

Wali Ullah Khan·Manzoor Ahmed·Chandan Kumar Sheemar·Marco Di Renzo·Eva Lagunas·Asad Mahmood·Syed Tariq Shah·Octavia A. Dobre·Jorge Querol·Symeon Chatzinotas

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Abstract

Beyond Diagonal Reconfigurable Intelligent Surfaces (BD-RIS) represent a groundbreaking innovation in sixth-generation (6G) wireless networks, enabling unprecedented control over wireless propagation environments compared to conventional diagonal RIS (D-RIS). This survey provides a comprehensive analysis of BD-RIS, detailing its architectures, operational principles, and mathematical modeling while highlighting its performance benefits. BD-RIS classifications, including single-connected, fully-connected, and group-connected architectures, and their reflective, transmissive, hybrid, and multi-sector operating modes are examined. Recent advances in BD-RIS-enabled 6G networks are reviewed, focusing on critical areas such as channel estimation, sum-rate and spectral efficiency optimization, energy efficiency enhancement, and security. The survey identifies fundamental challenges in BD-RIS research, including hardware design limitations, adaptive channel estimation, and the impact of non-ideal hardware effects. Future research directions for BD-RIS are proposed, emphasizing the integration of artificial intelligence and machine learning (AI/ML), joint optimization of communication and sensing, and enhanced physical layer security (PLS). This study concludes by underscoring BD-RIS's transformative potential to redefine 6G wireless networks, offering valuable insights and lessons for future research and development.

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Wali Ullah Khan, Manzoor Ahmed, Chandan Kumar Sheemar, Marco Di Renzo, Eva Lagunas, Asad Mahmood, Syed Tariq Shah, Octavia A. Dobre, Jorge Querol, Symeon Chatzinotas. 2025-03-24. Survey on Beyond Diagonal RIS Enabled 6G Wireless Networks: Fundamentals, Recent Advances, and Challenges. https://arxiv.org/abs/2503.08423

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