  Wireless communication environments comprise passive objects that cause
performance degradation and eavesdropping concerns due to anomalous scattering.
This paper proposes a new paradigm, where scattering becomes software-defined
and, subsequently, optimizable across wide frequency ranges. Through the
proposed programmable wireless environments, the path loss, multi-path fading
and interference effects can be controlled and mitigated. Moreover, the
eavesdropping can be prevented via novel physical layer security capabilities.
The core technology of this new paradigm is the concept of metasurfaces, which
are planar intelligent structures whose effects on impinging electromagnetic
waves are fully defined by their micro-structure. Their control over impinging
waves has been demonstrated to span from 1 GHz to 10 THz. This paper
contributes the software-programmable wireless environment, consisting of
several HyperSurface tiles (programmable metasurfaces) controlled by a central
server. HyperSurfaces are a novel class of metasurfaces whose structure and,
hence, electromagnetic behavior can be altered and controlled via a software
interface. Multiple networked tiles coat indoor objects, allowing fine-grained,
customizable reflection, absorption or polarization overall. A central server
calculates and deploys the optimal electromagnetic interaction per tile, to the
benefit of communicating devices. Realistic simulations using full 3D
ray-tracing demonstrate the groundbreaking performance and security potential
of the proposed approach in 2.4 GHz and 60 GHz frequencies.
