  The knowledge of channel covariance matrices is crucial to the design of
intelligent reflecting surface (IRS) assisted communication. However, channel
covariance matrices may change suddenly in practice. This letter focuses on the
detection of the above change in IRS-assisted communication. Specifically, we
consider the uplink communication system consisting of a single-antenna user
(UE), an IRS, and a multi-antenna base station (BS). We first categorize two
types of channel covariance matrix changes based on their impact on system
design: Type I change, which denotes the change in the BS receive covariance
matrix, and Type II change, which denotes the change in the IRS
transmit/receive covariance matrix. Secondly, a powerful method is proposed to
detect whether a Type I change occurs, a Type II change occurs, or no change
occurs. The effectiveness of our proposed scheme is verified by numerical
results.
