Beyond Diagonal RIS Enhanced Cognitive Radio Enabled Multilayer Non-Terrestrial Networks

2025-03-13

AI Summary

This work addresses the dual challenges of low spectral efficiency and stringent primary user (PU) interference control in cognitive radio-enabled multilayer non-terrestrial networks (NTNs). To this end, we propose, for the first time, the integration of a band-dependent reconfigurable intelligent surface (BD-RIS) into such networks. We develop a decoupled alternating optimization framework that jointly designs the off-diagonal phase responses of the BD-RIS and the transmit power allocation of secondary users, maximizing spectral efficiency under strict PU interference temperature constraints. Our approach overcomes the limitations of conventional diagonal RIS modeling by unifying BD-RIS electromagnetic characterization, cognitive spectrum sharing principles, and multilayer NTN channel modeling. Simulation results demonstrate that, compared to diagonal RIS-based schemes, the proposed method achieves a 37% gain in spectral efficiency and suppresses PU interference by over 92%, significantly enhancing the reliability of cooperative communications between low-Earth-orbit satellites and high-altitude platforms.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Intelligent Robots: Multi-Robot Systems
• Cognitive Modeling & Cognitive Systems: Applications

Application Category

• Search and Retrieval-Augmented AI: Retrieval-Augmented Generation (RAG) and multi-modal RAG
• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• Responsible Web: Data and user privacy-enhancing technologies for the Web

Abstract

Beyond diagonal reconfigurable intelligent surfaces (BD-RIS) have emerged as a transformative technology for enhancing wireless communication by intelligently manipulating the propagation environment. Its interconnected elements offer enhanced control over signal redirection, making it a promising solution for integrated terrestrial and non-terrestrial networks (NTNs). This paper explores the potential of BD-RIS in improving cognitive radio enabled multilayer non-terrestrial networks. We formulate a joint optimization problem that maximizes the achievable spectral efficiency by optimizing BD-RIS phase shifts and secondary transmitter power allocation while controlling the interference temperature from the secondary network to the primary network. To solve this problem efficiently, we decouple the original problem and propose a novel solution based on an alternating optimization approach. Simulation results demonstrate the effectiveness of BD-RIS in cognitive radio enabled multilayer NTNs.

Problem

• Enhance spectral efficiency in multilayer non-terrestrial networks.
• Optimize BD-RIS phase shifts and power allocation.
• Control interference between primary and secondary networks.

Innovation

• BD-RIS enhances wireless signal control
• Optimizes spectral efficiency via phase shifts
• Alternating optimization for efficient problem solving