Low Complexity Scheduling and Phase Shift Optimization in RIS-Aided mmWave Downlink Transmission

Abstract

We study the problem of multi-user scheduling, beamforming and phase shift optimization in Reconfigurable Intelligent Surface (RIS)-assisted mmWave downlink transmission. The proposed proportional fair scheduling algorithm takes into account the direct and cascade achievable rates and inter-user interference. In order for a RIS to be useful in mmWave band, extremely high number of RIS elements are required. This results in prohibitive complexity in channel estimation and beam-forming/phase shift optimization. In this work we also discussed and proposed solutions for low complexity beamforming and phase shift optimization. Performance of the proposed scheduling, beamforming and phase shift optimization solution is evaluated by simulations. Comparison with some benchmarks reveal that interference-aware proportional fair user scheduling results in significant performance gains. © 2023 IEEE.