Cascaded Channel Estimation Using Full Duplex for IRS-Aided Multiuser Communications

To achieve huge passive/reflect beamforming gain by intelligent reflecting surface (IRS), channel state information (CSI) on IRS is essential but challenging to obtain in IRS-aided systems due to the lack of signal transmitting/receiving/processing capabilities of IRS passive elements as well as the massive channel coefficients to be estimated. In this paper, we propose a new channel estimation scheme using the full-duplex technique for estimating the CSI of all users' cascaded channels in an IRS-aided multiuser communication system. Specifically, one arbitrarily selected reference user is equipped with the full-duplex technique in the channel estimation phase to estimate the element-wise squared channel between it and the IRS via its pilot transmission together with the IRS's time-varying reflection. Meanwhile, the base station (BS) and non-reference users estimate the CSI of their respective IRS-reflected channels, based on which the users-IRS-BS cascaded channels of the non-reference users are recovered by utilizing the fact that the IRS-BS channel is common to all users. As such, the proposed channel estimation scheme significantly reduces the required minimum training overhead for estimating all users-IRS-BS cascaded channels, which is determined by the number of IRS reflecting elements only, and is irrelevant to that of IRS-served users. Numerical results demonstrate the effectiveness of the proposed scheme.

Automated summary

This paper proposes a new channel estimation scheme using the full-duplex technique to estimate the channel state information (CSI) of all users' cascaded channels in a multiuser communication system. The proposed scheme significantly reduces the required training overhead and improves efficiency.