A Novel Hybrid Optical and STAR IRS System for NTN Communications

2025-08-05

AI Summary

To address the low spectral efficiency of optical/RF hybrid transmission between high-altitude platforms and ground users in non-terrestrial networks (NTNs), as well as the challenge of seamless indoor-outdoor coverage coordination, this paper proposes a novel five-hop hybrid free-space optical (FSO)/RF architecture integrating optical intelligent reflecting surfaces (OIRS) and simultaneously transmitting-and-reflecting intelligent reflecting surfaces (STAR-IRS). We innovatively formulate a multi-element OIRS channel model and employ the bivariate Fox-H function to derive high-accuracy closed-form expressions for key performance metrics. This work is the first to analytically characterize the system’s diversity gain at high SNR. Closed-form expressions for outage probability, ergodic capacity, and average bit error rate are jointly derived. Simulation results demonstrate that the proposed architecture significantly enhances link reliability and coverage flexibility—particularly under complex terrain conditions and dynamic user access scenarios.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Mixed Discrete/Continuous Search
• Intelligent Robots: Multi-Robot Systems

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Novel mobile and WoT systems, and system-of-systems
• Search and Retrieval-Augmented AI: Web evaluation methodologies and metrics
• Security and Privacy: Large-scale security measurements

Abstract

This paper proposes a novel non-terrestrial networks (NTNs) system that integrates optical intelligent reflecting surfaces (OIRS) and simultaneous transmitting and reflecting Intelligent reflecting surfaces (STAR-IRS) to address critical challenges in next-generation communication networks. The proposed system model features a signal transmitted from the optical ground station (OGS) to the earth station (ES) via an OIRS mounted horizontally on a high altitude platform (HAP). The ES uses an amplify-and-forward (AF) relay with fixed gain for signal relaying, which is then transmitted through a STAR-IRS vertically installed on a building to facilitate communication with both indoor and outdoor users. The FSO link incorporates (multiple-input multiple-output) MIMO technology, and this paper develops a channel model specifically designed for scenarios where the number of OIRS units exceeds one. For the radio-frequency (RF) link, a novel and highly precise approximation method is introduced, offering superior accuracy compared to traditional approaches based on the central limit theorem (CLT). Closed-form analytical expressions for key performance metrics, including outage probability (OP), ergodic capacity and average bit error rate (BER) are derived in terms of the bivariate Fox-H function for this novel five hops system. Asymptotic expressions at high SNR are also presented, providing insights into system diversity order.

Problem

• Integrates OIRS and STAR-IRS for next-gen NTN challenges
• Develops channel model for multi-OIRS MIMO FSO links
• Derives precise RF link metrics using Fox-H function

Innovation

• Hybrid OIRS and STAR-IRS for NTN
• MIMO FSO link with multi-OIRS
• Novel RF approximation method