Near-Field Range Estimation with Joint Spatial-Delay Processing for XL-MIMO OFDM ISAC

Integrated sensing and communication (ISAC) technology has emerged as a transformative approach to enhance spectrum efficiency and enable simultaneous high-precision sensing and communication in wireless systems. Conventional range estimation for ISAC mainly relies on estimating the signal delays, which fails to distinguish densely located targets if the allocated bandwidth is insufficient. Fortunately, the near-field effect of extremely large-scale multiple-input multiple-output (XL-MIMO) offers a new dimension for range estimation in the spatial domain. Therefore, this paper proposes an innovative range estimation algorithm based on joint spatial-delay processing for XL-MIMO orthogonal frequency division multiplexing (OFDM) ISAC. The range resolution of the proposed algorithm optimizes the performance by dynamically selecting the best resolution in the spatial-delay domain at different target distances. Simulation results show that the proposed method significantly outperforms the traditional scheme in the delay or spatial domain alone, especially for challenging scenarios when the bandwidth or antenna size are insufficient.