Sensing for Beamforming: An IRS-Enabled Integrated Sensing and Communication Framework

In this paper, we exploit the potential benefits of intelligent reflecting surface (IRS) in achieving integrated sensing and communication (ISAC) at the same frequency and time resources. To this end, we establish a novel framework, in which a single-antenna user transmits to a multi-antenna base station, with the aid of a distributed semi-passive IRS. In the established framework, the transmission period is divided into two time blocks. At each time block, the distributed semi-passive IRS conducts the location sensing and data transmission simultaneously. Simple-yet-efficient location sensing and beamforming design schemes are respectively proposed. Particularly, the estimated user location in the first time block is used to facilitate the beamforming design of the IRS in the second time block. Through numerical results, we demonstrate that the proposed location sensing scheme can achieve a millimeter-level positioning accuracy, even when the number of semi-passive reflecting elements is small and the allocated sensing time is short. In addition, we show that, utilizing the imperfect location information obtained from our proposed location sensing scheme, the proposed beamforming design scheme can achieve almost the same performance as the optimal beamforming scheme assuming the perfect channel state information, thus verifying the effectiveness of our proposed framework and providing valuable insights into the design of other IRS-enabled ISAC systems.