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原文摘要

This paper explores an integrated sensing and communication (ISAC) system with backscattering radio frequency identification (RFID) tags. In this setup, an access point employs communication beams to serve communication users while leveraging a sensing beam to interrogate RFID tags. Under the total transmit power constraint of the system, our objective is to design a joint sensing and communication beamforming codebook by considering the tag interrogation and communication requirements. To lay a foundation for the codebook design problem, we first study the beamforming design problem in the single-tag scenario and investigate two approaches: a two-stage zero-forcing-based design with optimized power allocation and a joint beamforming design that minimizes the total transmit power. Extending our study to the multi-tag scenario, we propose a site-specific beamforming codebook design. The proposed approach partitions the region of interest into angular sectors and jointly optimizes the sensing and communication beams for each sector. The simulation results show that the proposed beamforming designs can effectively mitigate the mutual interference between sensing and communication functionalities, thus enhancing the interrogation range of the tags while minimizing transmit power. Also, the efficacy of the proposed site-specific codebook design has been demonstrated in terms of interrogation success rate, offering a promising approach for ISAC backscattering systems.