Secure Rate-Splitting and RIS Beamforming with Untrusted Energy Harvesting Receivers

TL;DR

This paper introduces a secure rate-splitting scheme aided by UAV-mounted RIS to enhance physical-layer security and energy efficiency in a heterogeneous network with untrusted energy-harvesting receivers.

Contribution

It proposes a novel RIS-assisted secure rate-splitting method with an optimization framework for joint design, improving secrecy energy efficiency in complex networks.

Findings

The proposed algorithm outperforms SDMA and NOMA in secrecy energy efficiency.

The RIS-assisted scheme effectively balances energy transfer and security.

Simulation results confirm the scalability and superiority of the method.

Abstract

We consider a reconfigurable intelligent surface (RIS)-assisted heterogeneous network comprising legitimate information-harvesting receivers (IHRs) and untrusted energy-harvesting receivers (UEHRs). A multi-antenna base station (BS) transmits confidential information to IHRs while ensuring sufficient energy transfer to UEHRs that may attempt eavesdropping. To enhance physical-layer security, we propose a secure rate-splitting multiple access (RSMA) scheme aided by a UAV-mounted RIS. The objective is to maximize fairness-based secrecy energy efficiency (SEE). Owing to the non-convexity of the formulated problem, we develop an alternating optimization framework that jointly designs the common message allocation, active precoders, and RIS phase shifts under transmit power and energy harvesting constraints, leveraging sequential convex approximation (SCA). Simulation results demonstrate the scalability of the proposed algorithm and its superior SEE performance compared to space-division multiple access (SDMA) and non-orthogonal multiple access (NOMA) benchmarks.