Performance Analysis of RIS-Assisted UAV Communication in NOMA Networks

2025-10-02

AI Summary

This paper investigates performance optimization for RIS-enhanced UAV-assisted NOMA downlink transmission, focusing on outage behavior differences among direct, RIS-only, and composite links under mixed LoS/NLoS channels. To reconcile the trade-off between user fairness and system robustness in multi-UAV scenarios, we propose a bi-level joint optimization framework: an upper level dynamically allocates NOMA power to minimize the maximum outage probability, while a lower level jointly optimizes the number of reflecting elements per RIS to reduce hardware overhead. We establish, for the first time, a composite channel model based on dual Nakagami-𝑚 fading, derive a closed-form expression for the SNR cumulative distribution function, and design a low-complexity RIS-assisted UAV Outage Minimization (RUOM) algorithm. Simulation results demonstrate that the proposed method reduces the maximum outage probability by up to 42%, improves the user fairness index by 18%, and decreases the total number of RIS reflecting elements by 31%.

Technology Category

• Intelligent Robots: Learning & Optimization for ROB
• Search and Optimization: Mixed Discrete/Continuous Search
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems

Application Category

• User Modeling, Personalization and Recommendation: Fairness-aware retrieval and ranking
• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• Responsible Web: Machine-in-the-loop, human agency and autonomy

Abstract

This paper investigates the performance of downlink non-orthogonal multiple access (NOMA) communication in unmanned aerial vehicle (UAV) networks enhanced by partitionable reconfigurable intelligent surfaces (RISs). We analyze three types of links between base station (BS) and UAVs: direct, RIS-only indirect, and composite links, under both Line-of-Sight (LoS) and Non-LoS (NLoS) propagation. The RIS-only indirect link and direct link are modeled using double Nakagami-m and Nakagami-m fading, respectively, while the composite link follows a combined fading channel model. Closed-form expressions for the cumulative distribution function (CDF) of the received signal-to-noise ratio (SNR) are derived for all links, enabling tractable outage probability analysis. Then, we formulate a fairness-efficiency bilevel optimization problem to minimize the maximum outage probability among UAVs while minimizing the total number of required RIS reflecting elements. Accordingly, an RIS-assisted UAV Outage Minimization (RUOM) algorithm is proposed, which fairly allocates the NOMA power coefficients while minimizing the total number of RIS reflecting elements required, subject to NOMA-defined constraints, RIS resource limitations, and maximum allowable outage threshold. Simulation results validate the analytical models and demonstrate that the proposed RUOM algorithm significantly improves fairness and efficiency in BS-UAV communication.

Problem

• Analyzing outage probability in RIS-assisted UAV NOMA networks
• Optimizing fairness and efficiency in UAV communication systems
• Minimizing required RIS elements while reducing outage probability

Innovation

• Partitionable RIS enhances UAV NOMA networks
• Double Nakagami-m models RIS-only indirect links
• Bilevel optimization minimizes outage and RIS elements