CSI-Free Holographic Beamforming Enabled by Recordable and Reconfigurable Metasurface

Holographic beamforming is rapidly emerging as a pivotal architecture for next-generation wireless network design. However, despite its promising capabilities, current implementation methods—especially those utilizing reconfigurable holographic surfaces (RHSs)—face a critical limitation: they rely heavily on accurate channel state information (CSI). This dependency creates a significant operational bottleneck, largely due to the excessive pilot overhead necessary to estimate channels in large-scale antenna arrays. To overcome this challenge, we propose a novel hardware framework termed the recordable and reconfigurable metasurface (RRM). This architecture effectively eliminates the requirement for explicit CSI acquisition by leveraging a holographic recording technique. During the uplink phase, power sensors embedded within the RRM measure the intensity of the interference pattern resulting from the superposition of incident user signals and a local reference wave. Because this recorded pattern inherently captures the necessary spatial phase data of the incoming waves, it allows for the direct calculation of holographic beamforming weights, bypassing resource-heavy channel estimation procedures. Through comprehensive mutual information analysis, we verify that the proposed CSI-free RRM system delivers performance on par with an RHS system utilizing perfect CSI, while simultaneously offering significant reductions in both signaling overhead and computational complexity.