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：本文研究了由同时透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，为隐蔽发射机与接收机之间的通信存在性以规避监视者，利用配备双天线的友好全双工接收机协助混淆监视者。考虑最坏情形，推导了监视者最小检测错误概率（DEP）的闭式表达式，并将其作为隐蔽约束。随后，在隐蔽约束与通信中断分析下的服务质量（QoS）约束条件下，构建了以最大化系统隐蔽速率为目标的优化问题。为联合设计发射机与STAR-RIS的有源及无源波束赋形，提出了一种基于全局收敛移动渐近线方法（GCMMA）的迭代算法，以有效求解该非凸优化问题。仿真结果表明，所提出的STAR-RIS辅助方案性能显著优于传统RIS方案。