  This letter aims to clarify the impact of channel aging and phase noise on
the performance of intelligent reflecting surface-aided wireless systems. We
first model mathematically the outdated channel state information (CSI) due to
Doppler shifts and phase noise stemming from hardware impairment. Then, a
closed-form expression of achievable spectral efficiency under noisy and aged
CSI is theoretically derived. Some typical simulation results to numerically
demonstrate the performance impact are illustrated.
