  Multi-channel wireless systems have become a standard solution to address our
information society's ever-increasing demand for more information transfer. The
ultimate bound on the capacity such systems can achieve is the limited channel
diversity in a given propagation medium, and countless proposals to reduce
channel cross-talk by engineering software or hardware details of the signals
and antenna arrays have been proposed. Here we demonstrate the physical shaping
of the propagation medium itself to achieve optimal channel diversity. Using a
reconfigurable metasurface placed inside a random environment, we tune the
disorder and impose perfect orthogonality of wireless channels. We present
experiments in the microwave domain in which we impose equal weights of the
channel matrix eigenvalues for up to 4x4 systems, and almost equal weights in
larger systems. We further describe one example of wireless image transmission
in an office room in which we augmented the 3x3 system's number of effectively
independent channels from 2 to the optimum of 3.
