  To meet the stringent requirements of next-generation wireless networks,
multiple-input multiple-output (MIMO) technology is expected to become massive
and pervasive. Unfortunately, this could pose scalability issues in terms of
complexity, power consumption, cost, and processing latency. Therefore, novel
technologies and design approaches, such as the recently introduced holographic
MIMO paradigm, must be investigated to make future networks sustainable. In
this context, we propose the concept of a dynamic scattering array (DSA) as a
versatile 3D structure capable of performing joint wave-based computing and
radiation by moving the processing from the digital domain to the
electromagnetic (EM) domain. We provide a general analytical framework for
modeling DSAs, introduce specific design algorithms, and apply them to various
use cases. The examples presented in the numerical results demonstrate the
potential of DSAs to further reduce complexity and the number of radiofrequency
(RF) chains in holographic MIMO systems while achieving enhanced EM wave
processing and radiation flexibility for tasks such as beamforming and single-
and multi-user MIMO.
