Integrating Reconfigurable Intelligent Surface and AAV for Enhanced Secure Transmissions in IoT-Enabled RSMA Networks

Autonomous aerial vehicle (AAV)-enabled Internet of Things (IoT) exhibits great application potential with its wide coverage, flexible network topology, and diversified services. However, ensuring communication security and efficient spectrum resource utilization in multiuser access scenarios is challenging, given the open nature of AAV channels and the proliferation of communication devices in IoT. To address the above challenges, this article proposes a novel reconfigurable intelligent surface (RIS)-aided AAV collaborative communication framework, where RIS-equipped AAV flexibly serves multiple users. In this work, a rate splitting multiple access (RSMA)-based secure transmission scheme is proposed, where the split public information serves both as useful signals and noise to disrupt eavesdropping. For the proposed scheme, a sum secrecy rate maximization problem is formulated and solved by optimally deploying the AAV’s location, designing the RIS’s phase shift, and power allocation. For this nonconvex problem with a couple of variables, we decompose it and form three separate subissues. Specifically, leveraging the successive convex approximation (SCA) and semidefinite relaxation (SDR) techniques, we first exploit an iterative algorithm for optimizing beamforming vectors and phase-shift matrix of RIS, and the optimal position of the AAV is obtained according to the deep deterministic policy gradient (DDPG). Then, we design an alternating optimization (AO) framework for joint solving. Finally, simulation results validate the efficacy of the proposed scheme in enhancing security, e.g., relative to the nonorthogonal multiple access (NOMA) scheme and benchmark scheme, the secrecy rate of the proposed scheme increased by 29.7% and 71.9%, respectively.

I. Introduction

The Internet of Things (IoT), which consists of the Internet, sensor networks, and traditional telecommunications networks, is an important support for the next generation of communication technology. Facing the urgent requirements for efficient and seamless coverage, Autonomous aerial vehicle (AAV)-enabled IoT, having the advantages of cost-effective, high throughput, and flexible network architecture, have attracted widespread attention [1]. With high mobility and convenient deployment, AAVs can achieve efficient data transmission and comprehensive communication coverage as aerial relays and have been widely used in emergency rescue, intelligent transportation, and other fields [2]. However, AAVs face power limitations when forwarding information, and in complex urban scenarios, the air-to-ground channels are susceptible to interference from buildings or environmental fading, resulting in degraded channel quality. reconfigurable intelligent surface (RIS), composed of low-cost electromagnetic materials, offers a solution by reconfiguring channels through beamforming and parameter adjustments, thereby effectively enhancing backscatter communications and solving the above problems. Compared with traditional networks where RIS is fixed on the surface of buildings, AAV-RIS communication networks leverage flexible mobility and channel improvement capabilities and have superiority in improving communication performance, such as throughput and energy efficiency [3].