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：近期，同时透射与反射可重构智能表面（STAR-RIS）作为一项新兴技术，能够提供360度覆盖及新的自由度，并具备操纵信号传播与同时无线信息与功率传输（SWIPT）的能力。本文针对下行链路多输入单输出速率分裂多址（RSMA）网络，提出了一种新型STAR-RIS辅助的安全SWIPT系统。在该系统中，发射机与信息接收机（IRs）进行通信，同时向不可信能量接收机（UERs）发送能量。UERs亦具备窃听IRs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），但能量发射机仅掌握UERs的非完美CSI。通过利用RSMA，基站将IRs的消息分裂为公共部分与私有部分；前者编码为所有IRs均可解码的公共流，而私有消息则由各自对应的IRs单独解码。本文在总发射功率约束、UERs总能量约束以及透射与反射系数约束下，求解最大化IRs可达最坏情况保密和速率的预编码器与STAR-RIS配置。所构建的问题具有非凸性与高度耦合的变量。为应对这一挑战，本文提出了一种基于序列参数凸近似方法的次优两步迭代算法。仿真结果表明，基于RSMA的算法结合STAR-RIS，既能提升机密信息传输速率，又能提高总频谱效率。此外，本方法性能优于正交多址（OMA）与非正交多址（NOMA）。