In this paper, we investigate an active simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) assisted integrated sensing and communications (ISAC) system, where the dual-function base station (DFBS) operates in full-duplex (FD) mode to provide communication services and performs targets sensing simultaneously. Meanwhile, we consider multiple targets and multiple users scenario as well as the self-interference at the FD DFBS. Through jointly optimizing the DFBS and active STAR-RIS beamforming under different work modes, our purpose is to achieve the maximum communication sum-rate, while satisfying the minimum radar signal-to-interference-plus-noise ratio (SINR) constraint, the active STAR-RIS hardware constraints and the total power constraint of DFBS and active STAR-RIS. To tackle the complex non-convex optimization problem formulated, an efficient alternating optimization algorithm is proposed. Specifically, the fractional programming method is first leveraged to turn the original problem into a more tractable one, and subsequently the transformed problem is decomposed into several sub-problems. Next, we develop a derivation method to obtain the closed-form expression of the radar receiving beamforming, and then the DFBS transmit beamforming is optimized under the radar SINR requirement and total power constraints. After that, the active STAR-RIS reflection and transmission beamforming are optimized by majorization minimization, complex circle manifold and convex optimization techniques. Finally, the proposed schemes are conducted through numerical simulations to show their benefits and efficiency.

翻译：本文研究了一种主动式同时透射反射可重构智能表面辅助的集成感知与通信系统，其中双功能基站以全双工模式运行，在提供通信服务的同时执行目标感知任务。我们考虑了多目标、多用户场景以及全双工双功能基站的自干扰问题。通过在不同工作模式下联合优化双功能基站与主动式STAR-RIS的波束成形，我们的目标是在满足最小雷达信号干扰噪声比约束、主动式STAR-RIS硬件约束以及双功能基站与主动式STAR-RIS总功率约束的前提下，实现最大通信总速率。为处理所建立的复杂非凸优化问题，提出了一种高效交替优化算法。具体而言，首先利用分式规划方法将原始问题转化为更易处理的形式，随后将转换后的问题分解为若干子问题。接着，我们推导出雷达接收波束成形的闭式表达式，进而在雷达信号干扰噪声比要求与总功率约束下优化双功能基站发射波束成形。此后，通过主最小化、复圆流形及凸优化技术优化主动式STAR-RIS的反射与透射波束成形。最后通过数值仿真验证了所提方案的优势与有效性。