Near-Field Hybrid Beamforming Design for mmWave Integrated Sensing and Communication

In this paper, we investigate near-field hybrid beam-forming design for millimeter-wave (mmWave) integrated sensing and communication (ISAC) systems, where one base station (BS) equipped with large-scale antenna array simultaneously serves multiple communication users and performs target localization by exploiting the degrees of freedom in both angle and distance domains. First, to characterize the target localization accuracy, we analyze the squared position error bound (SPEB) for estimating the two-dimensional (2D) position of target. Then, the hybrid beamforming design is formulated to maximize the sum-rate of communication users, while guaranteeing the SPEB constraint of target localization, transmit power constraint, and constant modulus constraints. To tackle the nonconvex problem, we propose a fractional programming (FP) and successive convex approximation (SCA)-based block coordinate descent (BCD) algorithm. Simulation results demonstrate that the proposed hybrid beam-forming can achieve sum-rate close to fully-digital beamforming and outperform the baseline schemes.