Guest Editorial: Intelligent metasurfaces for smart connectivity

International audienceCurrent 5G wireless systems depend heavily on the quality of the wireless propagation environment, which had conventionally been modelled as an exogenous entity that can only be adapted and not controlled. This is challenged by future wireless networks which integrate communication, sensing, and localisation in a single platform, and where the wireless environment is not treated as part of the network design parameters. This new vision of wireless network design is enabled by an emerging technology of reconfigurable intelligent surfaces (RISs), also known as intelligent reflecting surfaces (IRSs). RISs are thin layers of electromagnetic metamaterials capable of shaping radio waves that impinge upon them in ways that the wireless environment can be customized to fulfil specific system requirements. As a result, metamaterial-based RISs can create favourable propagation conditions by controlling the phase and amplitude of the impinging radio waves through nearly passive and low-cost scattering elements. Recently, metasurfaces have received a surge in research and development interests in wireless communications and are seen as a promising transformative technology with the potential of fundamentally changing how wireless networks are implemented, optimized, and operated.This special issue aims to create a platform for researchers from both academia and industry to disseminate state-of-the-art results and to advance metasurface-empowered wireless networks. In total, 15 excellent papers were accepted after a rigorous multi-round review process. These papers can be divided into two topics: key techniques for metasurface-enabled multi-input–multi-output (MIMO) systems and integration of metasurfaces and existing wireless techniques. In the following, we will introduce these papers and highlight their contributions