Hybrid/Reflective Beamforming for IRS-Assisted Dual-Function Radar-Communication System

This article investigates the joint design problem of the hybrid/reflective beamforming for the dual-function radar-communication (DRC) system with the help of an intelligent reflecting surface (IRS). The degrees of freedom for beamformer design are the analog and digital beamformers (DBF) at the base station (BS), and the reflective beamformer (RBF) at the IRS. To begin with, we formulate the beamformer design problem as a weighted sum-rate (WSR) maximization problem subject to the transmit power and similarity between the designed beamformer and the reference one with desired beampattern property. Then, utilizing equivalent reformulation of the preceding design problem, we conceive an alternating direction sequential programming (ADSP)-based algorithm that iteratively updates the following low-complexity subproblems: 1) DBF at the BS through the Powell-Hestenes-Rockafellar (PHR) method; 2) analog beamformer at the BS using the Riemannian conjugate gradient method; and 3) RBF at the IRS by the successive convex approximation (SCA) technique. The convergence is ensured by analytically offering the nondecreasing and boundary of the WSR value. Finally, numerical results verify the effectiveness of the proposed algorithm, which achieves superior WSR performance while ensuring the radar requirement.