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

January 1, 2026·
Wali Ullah Khan
,
Chandan Kumar Sheemar
,
Manzoor Ahmed
,
Marco Di Renzo
,
Syed Tariq Shah
,
Asad Mahmood
,
Eva Lagunas
,
Jorge Querol
,
Symeon Chatzinotas
,
Zhu Han
· 2 min read
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.
Type
Publication
IEEE Open Journal of the Communications Society
publication

Abstract & Overview

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.

Publication Metadata

  • Authors: Wali Ullah Khan, Chandan Kumar Sheemar, Manzoor Ahmed, Marco Di Renzo, Syed Tariq Shah, Asad Mahmood, Eva Lagunas, Jorge Querol, Symeon Chatzinotas, Zhu Han
  • Venue: IEEE Open Journal of the Communications Society (2026)
  • Research Areas: 6G-NTN
  • DOI: 10.1109/ojcoms.2026.3734637
  • Open Access Repository: ORBiLu – University of Luxembourg
6G-NTN