This paper investigates the multi-antenna covert communications assisted by a simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS). In particular, to shelter the existence of communications between transmitter and receiver from a warden, a friendly full-duplex receiver with two antennas is leveraged to make contributions to confuse the warden. Considering the worst case, the closed-form expression of the minimum detection error probability (DEP) at the warden is derived and utilized as a covert constraint. Then, we formulate an optimization problem maximizing the covert rate of the system under the covertness constraint and quality of service (QoS) constraint with communication outage analysis. To jointly design the active and passive beamforming of the transmitter and STAR-RIS, an iterative algorithm based on globally convergent version of method of moving asymptotes (GCMMA) is proposed to effectively solve the non-convex optimization problem. Simulation results show that the proposed STAR-RIS-assisted scheme highly outperforms the case with conventional RIS.

翻译：本文研究了同时发射和反射可重构智能表面（STAR-RIS）辅助的多天线隐蔽通信。具体而言，为隐藏发射机与接收机之间的通信存在性以规避监控者，利用配备两根天线的友好型全双工接收机来迷惑监控者。考虑最坏情况，推导出监控端最小检测错误概率（DEP）的闭式表达式，并将其作为隐蔽约束。随后，我们构建了一个优化问题，在满足隐蔽性约束和通信中断分析得到的服务质量（QoS）约束条件下，最大化系统的隐蔽速率。为联合设计发射机与STAR-RIS的有源及无源波束赋形，提出一种基于全局收敛移动渐近线法（GCMMA）的迭代算法，以有效求解该非凸优化问题。仿真结果表明，所提STAR-RIS辅助方案性能显著优于传统RIS方案。