RIS Array Diagnosis for mmWave Communication Systems

Reconfigurable Intelligent Surface (RIS) can obtain huge passive beamforming gains. However, due to imperfect hardware and deployment environments, RIS is subject to hardware impairments (HWI) and partial elements blockage, resulting in a significant loss of gain. Hence, RIS array diagnosis is of great significance for normal operations of the RIS system. We consider a RIS assisted millimeter-wave (mmWave) communication system where some RIS elements suffer from HWI. A conjugate gradient complex soft threshold (CG-CST) algorithm is proposed to diagnose the RIS array, reducing the overhead and increasing the diagnostic accuracy. Furthermore, the proposed CG-CST algorithm is effective in both single-input single-output (SISO) systems and systems with multiple antennas. Numerical results confirm that the presented CG-CST algorithm has superior performance compared to existing methods.