  Analog to Digital Converters (ADCs) are a major contributor to the energy
consumption on the receiver side of millimeter-wave multiple-input
multiple-output (MIMO) systems with large antenna arrays. Consequently, there
has been significant interest in using low-resolution ADCs along with hybrid
beam-forming at MIMO receivers for energy efficiency. However, decreasing the
ADC resolution results in performance loss -- in terms of achievable rates --
due to increased quantization error. In this work, we study the application of
practically implementable nonlinear analog operations, prior to sampling and
quantization at the ADCs, as a way to mitigate the aforementioned rate-loss. A
receiver architecture consisting of linear analog combiners, implementable
nonlinear analog operators, and one-bit threshold ADCs is designed. The
fundamental information theoretic performance limits of the resulting
communication system, in terms of achievable rates, are investigated under
various assumptions on the set of implementable nonlinear analog functions. In
order to justify the feasibility of the nonlinear operations in the proposed
receiver architecture, an analog circuit is introduced, and circuit simulations
exhibiting the generation of the desired nonlinear analog operations are
provided.
