Rotatable Block-Controlled RIS: Bridging the Performance Gap to Element-Controlled Systems

TL;DR

This paper proposes a rotatable block-controlled RIS that reduces power consumption compared to element-controlled RIS while maintaining spectral efficiency, through innovative rotation and segmentation schemes.

Contribution

It introduces a novel BC-RIS design with single-phase control per block, achieving energy efficiency gains over traditional element-controlled RIS.

Findings

Achieves same spectral efficiency as element-controlled RIS

Significantly reduces power consumption

Numerical results confirm improved energy efficiency

Abstract

The passive reconfigurable intelligent surface (RIS) requires numerous elements to achieve adequate array gain, which linearly increases power consumption (PC) with the number of reflection phases. To address this, this letter introduces a rotatable block-controlled RIS (BC-RIS) that preserves spectral efficiency (SE) while reducing power costs. Unlike the element-controlled RIS (EC-RIS), which necessitates independent phase control for each element, the BC-RIS uses a single phase control circuit for each block, substantially lowering power requirements. In the maximum ratio transmission, by customizing specular reflection channels through the rotation of blocks and coherently superimposing signals with optimized reflection phase of blocks, the BC-RIS achieves the same averaged SE as the EC-RIS. To counteract the added power demands from rotation, influenced by block size, we have developed a segmentation scheme to minimize overall PC. Furthermore, constraints for rotation power-related parameters have been established to enhance the energy efficiency of the BC-RIS compared to the EC-RIS. Numerical results confirm that this approach significantly improves energy efficiency while maintaining performance.