Covert Performance of STAR-RIS-Assisted Wireless Powered Communication System with RSMA

This paper investigates covert communication in a simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) assisted wireless-powered communication (WPC) system employing rate splitting multiple access (RSMA). Specifically, the communication process is divided into two stages: energy transmission (ET) and information transmission (IT). In the ET stage, the energy-constrained user (U) and the cooperative jammer (J) harvest radio-frequency (RF) energy from the power station (PS). In the IT stage, U uses the harvested energy to transmit information to the access point (AP) via the STAR-RIS, while J uses the harvested energy to reflect artificial noise through the STAR-RIS. All channels are modeled under Nakagami-m fading. To evaluate covert performance, we derive the statistical characteristics of the cascaded channels, including the probability density function (PDF) and the cumulative distribution function (CDF). Based on these results, we derive expressions for the detection error probability (DEP), outage probability (OP) and covert rate (CR), and further conduct an asymptotic analysis of the OP and derive a lower bound on the CR. Finally, we examine the impact of key parameters on system performance. The simulation results show that, compared with the baseline scheme, the proposed scheme achieves better covert performance and improved robustness against fading, providing support for secure communication in sensitive 6G scenarios.