Wideband Channel Estimation for IRS-Aided Systems in the Face of Beam Squint

Intelligent reflecting surfaces (IRSs) improve both the bandwidth and energy efficiency of wideband communication systems by using low-cost passive elements for impinging signals with adjustable phase shifts. To realize full potential IRS-aided systems, having accurate channel state information (CSI) is indispensable, but it challenging to acquire, since these devices cannot carry out transmit/receive signal processing. The existing estimation methods conceived only consider channel’s frequency selectivity, ignore effect beam squint, despite its severe performance degradation. Hence we fill this gap conceive explicitly taking squint into consideration. We demonstrate that mutual correlation function between spatial steering vectors cascaded two-hop reflected IRS has two peaks, which leads a pair estimated angles single propagation path, due squint. One frequency-independent ‘actual angle’, while other one frequency-dependent ‘false angle’. reduce influence false on estimation, propose twin-stage orthogonal matching pursuit (TS-OMP) algorithm, where path are obtained in first stage, gains delays second stage. Moreover, bespoke pilot design exploiting specific characteristics cross-entropy theory achieving an improved performance. Our simulation results superiority proposed algorithm over their conventional counterparts.