IRS Backscatter Enabled Uplink Multi-User Communications Coexisting With Radar Sensing

This correspondence studies intelligent reflecting surface (IRS) backscatter enabled uplink multi-user communications coexisting with radar sensing. In the system, the radar signal for target detection is harnessed by multiple users, each connected to one IRS that can send information to the base station through backscatter communications in a mode of time division multiple access. Our goal is to maximize the weighted sum bits per unit bandwidth for the uplink multi-user communications by jointly optimizing the transmitting signal at the radar, the passive beamforming at the IRSs, the time allocation among all the users, and the receiving beamforming at the radar, while guaranteeing the echo reception at the radar. To tackle the non-convex optimization problem, a method of alternative optimization as well as fractional programming is developed. The simulation results validate the feasibility of the considered system and show the communication performance with sensing.