Recently, simultaneously transmitting and reflecting reconfigurable intelligent surfaces (STAR-RISs) have emerged as a novel technology that provides 360 coverage and new degrees-of-freedom (DoFs). They are also capable of manipulating signal propagation and simultaneous wireless information and power transfer (SWIPT). This paper introduces a novel STAR-RIS-aided secure SWIPT system for downlink multiple input single output rate-splitting multiple access (RSMA) networks. The transmitter concurrently communicates with the information receivers (IRs) and sends energy to untrusted energy receivers (UERs). The UERs are also capable of wiretapping the IR streams. We assume that the channel state information (CSI) of the IRs is known at the information transmitter, but only imperfect CSI for the UERs is available at the energy transmitter. By exploiting RSMA, the base station splits the messages of the IRs into common and private parts. The former is encoded into a common stream that can be decoded by all IRs, while the private messages are individually decoded by their respective IRs. We find the precoders and STAR-RIS configuration that maximizes the achievable worst-case sum secrecy rate of the IRs under a total transmit power constraint, a sum energy constraint for the UERs, and subject to constraints on the transmission and reflection coefficients. The formulated problem is non-convex and has intricately coupled variables. To tackle this challenge, a suboptimal two-step iterative algorithm based on the sequential parametric convex approximation method is proposed. Simulations demonstrate that the RSMA-based algorithm implemented with a STAR-RIS enhances both the rate of confidential information transmission and the total spectral efficiency. Furthermore, our method surpasses the performance of both orthogonal multiple access (OMA) and non-OMA (NOMA).

翻译：近年来，同时透射与反射可重构智能表面（STAR-RIS）作为一种能够提供360度覆盖并引入新自由度（DoFs）的新兴技术而出现。该技术还能够调控信号传播并实现同时无线信息与功率传输（SWIPT）。本文提出了一种用于下行链路多输入单输出速率分割多址接入（RSMA）网络的新型STAR-RIS辅助安全SWIPT系统。发射机同时与信息接收机（IRs）通信并向非可信能量接收机（UERs）传输能量。UERs也具备窃听IR信息流的能力。我们假设信息发射机已知IRs的信道状态信息（CSI），但能量发射机仅能获取UERs的不完美CSI。通过利用RSMA，基站将IRs的消息分割为公共部分和私有部分。公共部分被编码为所有IRs均可解码的公共流，而私有消息则由各自的IRs独立解码。在总发射功率约束、UERs总能量约束以及透射与反射系数约束条件下，我们寻求能够最大化IRs可达最差情况总保密速率的预编码器和STAR-RIS配置方案。该问题具有非凸性且变量高度耦合。为应对这一挑战，本文提出了一种基于序列参数凸逼近方法的次优两步迭代算法。仿真结果表明，结合STAR-RIS实现的RSMA算法不仅提升了保密信息传输速率，还提高了总频谱效率。此外，本方法在性能上超越了正交多址接入（OMA）与非正交多址接入（NOMA）方案。