Beyond diagonal reconfigurable intelligent surface (BD-RIS) is a novel branch
of RIS which breaks through the limitation of traditional RIS with diagonal
scattering matrices. However, the existing research focuses on BD-RIS with
fixed architectures regardless of channel state information (CSI), which limit
the achievable performance of BD-RIS. To solve this issue, in this paper, we
propose a novel dynamically group-connected BD-RIS based on a dynamic grouping
strategy. Specifically, RIS antennas are dynamically divided into several
subsets adapting to the CSI, yielding a permuted block-diagonal scattering
matrix. To verify the effectiveness of the proposed dynamically group-connected
BD-RIS, we propose an efficient algorithm to optimize the BD-RIS with dynamic
grouping for a BD-RIS-assisted multi-user multiple-input single-output system.
Simulation results show that the proposed dynamically group-connected
architecture outperforms fixed group-connected architectures.Comment: 6 pages, 6 figures, accepted by IEEE Trans. Veh. Techno