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的可重构智能表面（STAR-RIS）辅助的多天线隐蔽通信。具体而言，为隐蔽收发器之间的通信存在性以对抗监听者，利用一个配备双天线的友好全双工接收器来协助混淆监听者。在最坏情况下，推导了监听者处最小检测错误概率（DEP）的闭式表达式，并将其作为隐蔽约束条件。随后，在通信中断分析下，我们构建了一个在隐蔽约束与服务质量（QoS）约束下最大化系统隐蔽速率的优化问题。为联合设计发送器与STAR-RIS的有源和无源波束成形，提出了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，所提出的STAR-RIS辅助方案在性能上显著优于采用传统RIS的情况。