Stacked intelligent metasurfaces (SIM) have recently emerged as a promising technology, which can realize transmit precoding in the wave domain. In this paper, we investigate a SIM-aided integrated sensing and communications system, in which SIM is capable of generating a desired beam pattern for simultaneously communicating with multiple downlink users and detecting a radar target. Specifically, we formulate an optimization problem of maximizing the spectrum efficiency, while satisfying the power constraint of the desired direction. This requires jointly designing the phase shifts of the SIM and the power allocation at the base station. By incorporating the sensing power constraint into the objective functions as a penalty term, we further simplify the optimization problem and solve it by customizing an efficient gradient ascent algorithm. Finally, extensive numerical results demonstrate the effectiveness of the proposed wave-domain precoder for automatically mitigating the inter-user interference and generating a desired beampattern for the sensing task, as multiple separate data streams transmit through the SIM.

翻译：堆叠智能超表面（SIM）作为一种新兴技术，可在波域实现发射预编码。本文研究了一种基于SIM的集成感知与通信系统，该系统能够生成期望的波束方向图，以同时与多个下行用户通信并探测雷达目标。具体而言，我们构建了一个在满足期望方向功率约束条件下最大化频谱效率的优化问题，这需要联合设计SIM的相位偏移与基站的功率分配。通过将感知功率约束作为惩罚项引入目标函数，我们进一步简化了优化问题，并通过定制高效的梯度上升算法进行求解。最终，大量数值结果表明，当多个独立数据流通过SIM传输时，所提出的波域预编码器能有效抑制用户间干扰，并为感知任务生成理想的波束方向图。