Reconfigurable Wireless Relaying With Multi-UAV-Carried Intelligent Reflecting Surfaces

Intelligent reflecting surface (IRS) can reconfigure wireless environment to improve channel capacity and extend coverage. In this paper, we develop a reconfigurable wireless relaying system aided by multiple unmanned aerial vehicle (UAV)-carried intelligent reflecting surfaces (IRSs), where both the significant active and passive beamforming gain brought by base station (BS) and IRS and the flexibility of UAV is exploited to enhance multiuser downlink transmission. Specifically, we jointly optimize UAVs' placement, active beamforming and power allocation at the BS, and passive beamforming at the UAV-IRSs to maximize the weighted sum rate. To address the corresponding optimization problem, we decompose it into several subproblems, which are iteratively optimized. Based on simulation results, the proposed scheme achieves significant performance gains over the benchmark schemes.