  Recent years have seen the emergence of programmable metasurfaces, where the
user can modify the EM response of the device via software. Adding
reconfigurability to the already powerful EM capabilities of metasurfaces opens
the door to novel cyber-physical systems with exciting applications in domains
such as holography, cloaking, or wireless communications. This paradigm shift,
however, comes with a non-trivial increase of the complexity of the
metasurfaces that will pose new reliability challenges stemming from the need
to integrate tuning, control, and communication resources to implement the
programmability. While metasurfaces will become prone to failures, little is
known about their tolerance to errors. To bridge this gap, this paper examines
the reliability problem in programmable metamaterials by proposing an error
model and a general methodology for error analysis. To derive the error model,
the causes and potential impact of faults are identified and discussed
qualitatively. The methodology is presented and exemplified for beam steering,
which constitutes a relevant case for programmable metasurfaces. Results show
that performance degradation depends on the type of error and its spatial
distribution and that, in beam steering, error rates over 20% can still be
considered acceptable.
