In this paper, we explore an integrated sensing and communication (ISAC) system with backscattering RFID tags. In this setup, an access point employs a communication beam to serve a user while leveraging a sensing beam to detect an RFID tag. Under the total transmit power constraint of the system, our objective is to design sensing and communication beams by considering the tag detection and communication requirements. First, we adopt zero-forcing to design the beamforming vectors, followed by solving a convex optimization problem to determine the power allocation between sensing and communication. Then, we study a joint beamforming design problem with the goal of minimizing the total transmit power while satisfying the tag detection and communication requirements. To resolve this, we re-formulate the non-convex constraints into convex second-order cone constraints. The simulation results demonstrate that, under different communication SINR requirements, joint beamforming optimization outperforms the zero-forcing-based method in terms of achievable detection distance, offering a promising approach for the ISAC-backscattering systems.

翻译：本文探讨了一种集成反向散射RFID标签的感知与通信（ISAC）系统。在该系统中，接入点利用通信波束为用户提供服务，同时借助感知波束检测RFID标签。在系统总发射功率约束下，我们的目标是在考虑标签检测与通信需求的基础上设计感知波束与通信波束。首先，我们采用迫零方法设计波束赋形向量，随后通过求解凸优化问题确定感知与通信之间的功率分配。接着，我们研究了一个联合波束赋形设计问题，目标是在满足标签检测与通信需求的同时最小化总发射功率。为解决该问题，我们将非凸约束重新表述为凸二阶锥约束。仿真结果表明，在不同通信信干噪比要求下，联合波束赋形优化在可达检测距离方面优于基于迫零的方法，为ISAC-反向散射系统提供了一种有前景的方案。