PHY0 network: Metasurface as PHY-beam router, is it possible? Challenges and open problems

A software-controlled metasurface is introduced as one of the key enablers of Sixth Generation (6G) communication. Some sort of wireless channel customization/ adaptation is allowed for the first time. As an extreme case for wireless channel adaptation, environmental beam routing has emerged for guiding Electromagnetic (EM) wireless transmission through multiple Reconfigured Intelligent Surfaces (RISs). This gives rise to instituting a new form of a physical networking layer (PHY0) that is hardly explored. Furthermore, there is a knowledge gap in the definition, functionalities, and limitations of the metasurface as a beam router. So, in this paper, we are aiming at highlighting the birth of a new physical layer networking technology. The environmental routing concept is introduced as an optimal wireless channel adaptation through "Open-air EM Guiding". Furthermore, the definition and functionality of RIS as an EM beam router are put forward as an ideal model. The limitations facing RIS in simulating the beam routing role are explored from the communication system viewpoint along with reviewing the state-of-the-art solutions resolving these limitations. Physicists and material engineers are motivated for providing better solutions for these challenges.