Reconfigurable Holographic Metasurface Aided Wideband OFDM Communications Against Beam Squint

The future sixth-generation wireless communications are expected to realize an intelligent network of low powered and high throughput transmissions. In response to such demands, the reconfigurable holographic metasurface (RHS) is evolving into a promising solution owing to its flexible beam steering capability with low power and hardware costs. Unlike traditional phased antenna arrays with independent phase shifters, the RHS can generate desired beams by radiation amplitude control of the reference wave propagating along the metasurface. This so-called holographic interference technique enables an ultra-thin, small-sized planar antenna structure, which is suitable for integrated implementation without any complex phase-shifting or power-division circuits. In this paper, we consider an RHS-aided wideband communication system with an RHS-equipped base station. We aim to maximize the achievable data rate via joint digital beamforming (DBF) and holographic beamforming (HBF). To defeat the beam squint loss brought by the frequency-selective nature, we leverage the additivity of holographic interference patterns to design a novel amplitude control algorithm for solving the HBF subproblem, which contributes to our proposed joint DBF and HBF scheme. Simulation results validate the effectiveness of the proposed scheme against the beam squint issue in terms of the achievable rate.