IRS-Aided Wideband Dual-Function Radar-Communications with Quantized Phase-Shifts

Intelligent reflecting surfaces (IRS) are increasingly considered as an emerging technology to assist wireless communications and target sensing. In this paper, we consider the quantized IRS-aided wideband dual-function radar-communications system with multi-carrier signaling. Specifically, the radar receive filter, frequency-dependent transmit beamforming and discrete phase-shifts are jointly designed to maximize the average signal-to-interference-plus-noise ratio (SINR) for radar while guaranteeing the communication SINR among all users. The resulting optimization problem has a fractional quartic objective function with difference of convex and discrete phase constraints and is, therefore, highly non-convex. Thus, we solve this problem via the alternating maximization framework, in which the alternating direction method of multipliers and Dinkelbach's algorithm are integrated to tackle the related subproblems. Numerical results demonstrate that the proposed method, even with the low-resolution IRS, achieves better sensing performance compared with non-IRS system.