results by exploiting the large system limit can be obtained. On the other hand, for IRS-aided wireless systems where knowledge of instantaneous CSI is required, there are in general two approaches for the channel acquisition, depending on whether the IRS elements are equipped with receiving RF chains [@qqmag]. For the first approach where IRS elements are capable of both sensing and reflecting, conventional channel estimation methods can be readily applied. Specifically, channels between the IRS and the BS/users can be estimated by leveraging channel reciprocity and time division duplexing (TDD). However, equipping the IRS elements with (receive) RF chains generally results in higher implementation cost and energy consumption. In contrast, for the second approach where no sensors are installed on the IRS (i.e., the IRS elements are purely passive), it is impossible to explicitly obtain the individual channels of the BS-IRS and IRS-user links. One possible method for this (more challenging) case presented in [@qqmag] is to bypass the channel estimation and design the passive beamforming coefficients directly based on the feedback from the BSs/users (e.g., using codebook-based passive beamforming), which, unfortunately, can be time-consuming due to practically vast number of IRS elements and the potentially large codebook size required 