Fig. 3

Three novel wireless communication architectures based on intelligent metasurfaces. a Conceptual illustration of non-modulated-metasurface backscatter wireless communication connecting the digital world and physical world, which is achieved by allocating RF source, nonlinear mixer, wideband power amplifier, and other necessary circuits. Here, the intelligent metasurface, usually called RIS in the community of communication, can be regarded as a passive relay or extension part of conventional antenna arrays. Several examples of NBWC are provided in c–e. b Potential applications of RIS in smart radio environment [171], c system model for IRS-assisted secure communication system [174], d illustration of the RIS-based computation off-loading in mobile edge computing system [176]. e Conceptual illustration of modulated-metasurface backscatter wireless communication by deploying an RF source and intelligent metasurface. Here, the digital information to be transferred is directly encoded into the metasurface on the physical level, and the signal modulation is achieved by the wave-metasurface interaction. Specifically, the intelligent metasurface plays two roles: mixer and antenna. Several examples of MMBWC are provided in f–h. f Schematic illustration of the operational mechanism of the direct modulation wireless communication system in [183], g experimental scenario of the dual-channel wireless communication system based on the space–time-coding digital metasurface [184]. h A photo of the metasurface-based MIMO wireless communication prototype [180]. i Conceptual illustration of ambient modulated-metasurface backscatter wireless communication by an intelligent metasurface. The intelligent metasurface plays three critical roles: mixer, antenna, energy harvest collector. j–l The demo system of AMMBC proposed Zhao et al. and some selected results [186]. Figures adapted with permission from: (b)–(d) IEEE, (f)–(g) under a CC BY 4.0 license, (h) IEEE, (j)–(l) under a CC BY 4.0 license