Development of scheduling methods in millimeter-wave communication using mountable reconfigurable intelligent surfaces on unmanned aerial vehicles

In recent years, with the increasing demand for data speed and the number of users, research in the field of communication has focused on fifth-generation (5G) technologies and beyond. Communication using millimeter-wave frequencies is one of the techniques targeted for 5G and beyond to address the challenges of data speed and capacity. Additionally, the use of unmanned aerial vehicles (UAVs), also known as drones, for communication purposes has become more widespread, particularly in natural disasters and public safety situations. UAVs offer advantages in emergency situations due to their ability to operate at high altitudes and be easily deployed. Furthermore, the utilization of reconfigurable intelligent surfaces (RIS) is proposed for 5G and beyond. RIS consists of passive elements that can adjust the phase of incoming signals to direct them towards specific locations. By placing an RIS on a UAV, the directions in which signals received from the base station are transmitted can be adjusted. The combination of UAVs and RIS aims to overcome various challenges in millimeter-wave communication. A hybrid beamforming technique will be employed for the base station. Hybrid beamforming combines discrete Fourier transform (DFT) codebook-based transmission beamforming for analog beamforming and zero-forcing (ZF) beamforming for digital beamforming. Additionally, the phase shifts of RIS elements have been optimized using DFT-based codebook optimization and alternative optimization techniques. To ensure fair scheduling of users, an interference-aware fair proportional scheduling algorithm has been developed. The performance impact of RIS deployment has been examined through various comparisons with proportional fair scheduling and hybrid beamforming.