Holographic Communications Enabled by Fluid RIS: Holographic Parameter Reconstruction and Beamforming

Recently, reconfigurable intelligent surfaces (RIS) technology has been researched to realize holographic communications, by utilizing its property of ultra-dense element spacing. However, the position-fixed RIS can only take advantage of phase-shift domain and reconfigurable holographic surfaces (RHS) can only take advantage of the amplitude domain. Furthermore, most of the previous researches only realize the holographic beamforming, which is only part of the holography theory. Therefore, to leverage the full potential of holography theory, a Fluid-RIS-enabled system is proposed to utilize holographic parameter reconstruction process to circumvent the challenging RIS channel estimation process. Furthermore, ideal and practical communication scenarios are considered, in which the two types of interference are different from the optical holography scenarios. The first type of interference stems from the background noise in the communication environment, and the second type of interference arises from the hardware impairment or phase shift error of the RIS system. To address these challenges, algorithms are proposed to eliminate the influence of second type of interference, even in the simultaneous presence of both interference sources. Consequently, we can perfectly reconstruct the channels’ information as well as the interferences’ information. Finally, simulation results verify the effectiveness and necessity of the proposed algorithms.