Adaptive Perturbation-Based Opportunistic Beamforming Design in Limited Feedback IRS-Assisted mmWave Systems

Millimeter-wave (mmWave) communication is able to provide high-speed data rates up to Gbps. However, mmWave communication is susceptible to fading and blockage by obstacles in indoor and urban areas owing to high path loss and directivity. To tackle these issues, the intelligent reflecting surface (IRS) is regarded as an effective technique that provides reflected signals to enhance system performance. However, designing the joint active and passive beamforming is challenging in the IRS-assisted mmWave communication systems owing to the time-varying channels. In this study, we propose a novel adaptive perturbation-based opportunistic beamforming design for IRS-assisted systems (IRS-APOBF) for mmWave channels. The proposed scheme employs adaptive perturbation to select the beamforming and phase-shift vectors that improve the system performance by enhancing the signal-to-noise ratio (SNR) of the received signal. Moreover, the proposed IRS-APOBF scheme can adapt to the time-varying channel conditions of IRS-assisted mmWave systems with the only requirement of SNR feedback from mobile stations, making it suitable for practical scenarios. The simulation outcomes reveal that the system throughput achieved by the IRS-APOBF scheme is significantly higher than that obtained via a conventional IRS-assisted opportunistic beamforming scheme, despite both schemes requiring limited feedback information.