This paper investigates an integrated sensing and communication (ISAC) system with reconfigurable intelligent surface (RIS). Our simultaneous beam training and target sensing (SBTTS) scheme enables the base station to perform beam training with the user terminals (UTs) and the RIS, and simultaneously to sense the targets. Based on our findings, the energy of the echoes from the RIS is accumulated in the angle-delay domain while that from the targets is accumulated in the Doppler-delay domain. The SBTTS scheme can distinguish the RIS from the targets with the mixed echoes from the RIS and the targets. Then we propose a positioning and array orientation estimation (PAOE) scheme for both the line-of-sight channels and the non-line-of-sight channels based on the beam training results of SBTTS by developing a low-complexity two-dimensional fast search algorithm. Based on the SBTTS and PAOE schemes, we further compute the angle-of-arrival and angle-of-departure for the channels between the RIS and the UTs by exploiting the geometry relationship to accomplish the beam alignment of the ISAC system. Simulation results verify the effectiveness of the proposed schemes.

翻译：本文研究了一种集成可重构智能表面（RIS）的通信与感知一体化（ISAC）系统。我们提出的同时波束训练与目标感知（SBTTS）方案使基站能够同时与用户终端（UT）和RIS进行波束训练，并实现对目标的感知。基于研究发现，来自RIS的回波能量在角度-时延域累积，而来自目标的回波能量在多普勒-时延域累积。SBTTS方案能够通过RIS与目标混合回波的特性区分RIS和目标。随后，我们提出了一种基于SBTTS波束训练结果的位置与阵列姿态估计（PAOE）方案，该方案适用于视距信道和非视距信道，通过开发低复杂度的二维快速搜索算法实现。基于SBTTS和PAOE方案，我们进一步利用几何关系计算RIS与UT之间信道的到达角和离开角，从而完成ISAC系统的波束对准。仿真结果验证了所提方案的有效性。