IRS-aided Multi-cell mmWave Communication Systems for Suppressing Interference

Intelligent reflecting surface (IRS) has recently been envisioned as a cost-effective solution to enhance the received signal power of the desired user and to suppress interference of the unintended user. In this paper, we investigate the IRS-aided multi-cell millimeter wave (mmWave) communication system for suppressing inter-cell interference (ICI) to assist the downlink transmission of cell-edge users. We aim for maximizing the minimum weighted signal-to-interference-plus-noise ratio (SINR) through jointly optimizing the active beamforming vectors of mmWave base stations (MBSs), the phase shifts of the IRS, and the location of the IRS in the case of imperfect CSI. To tackle this non-convex problem, we propose a majorization-minimization (MM)-based beamforming algorithm, in which three sets of variables can be updated alternately. The proposed algorithm is also extended to multi-IRS-aided multi-cell mmWave scenarios. The simulation results show the advantages in terms of the SINR of cell-edge users after introducing the IRS to mitigate the ICI.