  The recent development of metasurfaces has shown the potential to
significantly improve the performance of wireless communication networks by
manipulating the propagation environment with nearly-passive sub-wavelength
scattering elements arranged on a surface. However, most studies of this
technology focus on the reflective implementation of metasurfaces, i.e., the
surface reflects the impinged signals towards receivers located at the same
side of the transmitter, which restricts the coverage to one side of the
surface. In this article, we introduce the concept of intelligent omni-surfaces
(IOSs), which is able to serve mobile users on both sides of the surface to
achieve full-dimensional communications by its reflective and transmissive
properties. The working principle of the IOS is introduced and a novel hybrid
beamforming scheme is proposed for IOS-based wireless communications. Moreover,
we present a prototype of IOS-based wireless communications and report
experimental results. Furthermore, potential applications of the IOS to
wireless communications together with relevant research challenges are
discussed.
