Multi-Layer RIS on Edge: Communication, Computation and Wireless Power Transfer

The rapid expansion of Internet of Things (IoT) and its integration into various applications high-light the need for advanced communication, computation, and energy transfer techniques. However, the traditional hardware-based evolution of communication systems faces challenges due to exces-sive power consumption and prohibitive hardware cost. With the rapid advancement of reconfigu-rable intelligent surface (RIS), a new approach by parallel stacking a series of RIS, i.e., multi-lay-er RIS, has been proposed. Benefiting from the characteristics of scalability, passivity, low cost, and enhanced computation capability, multi-layer RIS is a promising technology for future massive IoT scenarios. Thus, this article proposes a multi-layer RIS-based universal paradigm at the network edge, enabling three functions, i.e., multiple-input multi-ple-output (MIMO) communication, computation, and wireless power transfer (WPT). Starting by pic-turing the possible applications of multi-layer RIS, we explore the potential signal transmission links, energy transmission links, and computation pro-cesses in IoT scenarios, showing its ability to handle on-edge IoT tasks and associated green challeng-es. Then, these three key functions are analyzed respectively in detail, showing the advantages of the proposed scheme, compared with the traditional hardware-based scheme. To facilitate the implementation of this new paradigm into reality, we list the dominant future research directions at last, such as inter-layer channel modeling, resource allocation and scheduling, channel estimation, and edge training. It is anticipated that multi-layer RIS will contribute to more energy-efficient wireless networks in the future by introducing a revolution-ary paradigm shift to an all-wave-based approach.