Active Beyond-Diagonal Reconfigurable Intelligent Surface with Hybrid Transmitting and Reflecting Mode

2026-04-15

AI Summary

This work addresses the limitations of conventional passive reconfigurable intelligent surfaces (RISs)—including restricted full-space coverage, lack of signal amplification, and insufficient beamforming flexibility—by proposing a novel active non-diagonal RIS (BD-RIS) architecture that uniquely integrates active amplification, hybrid transmissive–reflective operation, and a non-diagonal interconnect topology. By designing configurable unit-cell connectivity patterns (single-, group-, or fully connected) supporting both reciprocal and non-reciprocal configurations, and by developing a unified joint optimization framework that co-designs base station precoding with the RIS’s phase and amplitude responses, the proposed scheme achieves significantly higher system sum-rate under the same total power budget compared to existing active/passive transmit–reflect RISs and passive BD-RISs, thereby demonstrating the substantial gains in full-space beamforming efficiency enabled by the synergy of active amplification, flexible interconnectivity, and hybrid mode operation.

Technology Category

• Multiagent Systems: Agent/AI Theories and Architectures
• Search and Optimization: Mixed Discrete/Continuous Search
• Cognitive Modeling & Cognitive Systems: Agent Architectures

Application Category

• Search and Retrieval-Augmented AI: Retrieval-Augmented Generation (RAG) and multi-modal RAG
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation
• Systems and Infrastructure for Web, Mobile and WoT: Applied ML and AI for Web-based mobile applications

Abstract

Beyond-diagonal reconfigurable intelligent surfaces (BD-RISs), originally in the passive form, have attracted attention due to their benefits in enhanced wave manipulating through flexible inter-element connections and element arrangements. To mitigate the severe multiplicative fading, the concept of active BD-RISs with signal amplification capability has recently been proposed. Inspired by this, we investigate the hybrid transmitting and reflecting mode of active BD-RISs to achieve full-space coverage. We start by deriving a physics compliant communication model applying active BD-RIS with hybrid mode. We further propose novel architectures including reciprocal and non-reciprocal implementations with cell-wise single, group, and fully connections. We also develop a unified optimization framework for the joint transmit precoding and hybrid mode active BD-RIS design to maximize the sum rate of multi-user communication systems, which is applicable to all considered architectures. Numerical results demonstrate that, under the same total power budget, the proposed active BD-RIS with hybrid mode substantially outperforms active and passive simultaneous transmitting and reflecting RISs as well as passive BD-RISs with hybrid mode. This shows the synergy gain from inter-element connection, element arrangements, and active amplification.

Problem

• Reconfigurable Intelligent Surface
• Multiplicative Fading
• Full-Space Coverage
• Active RIS
• Hybrid Transmitting and Reflecting

Innovation

• Active BD-RIS
• Hybrid Transmitting and Reflecting
• Inter-element Connection
• Unified Optimization Framework
• Full-space Coverage