  Motivated by the demand for energy-efficient communication solutions in the
next generation cellular network, a mixed-ADC architecture for massive multiple
input multiple output (MIMO) systems is proposed, which differs from previous
works in that herein one-bit analog-to-digital converters (ADCs) partially
replace the conventionally assumed high-resolution ADCs. The
information-theoretic tool of generalized mutual information (GMI) is exploited
to analyze the achievable data rates of the proposed system architecture and an
array of analytical results of engineering interest are obtained. For fixed
single input multiple output (SIMO) channels, a closed-form expression of the
GMI is derived, based on which the linear combiner is optimized. The analysis
is then extended to ergodic fading channels, for which tight lower and upper
bounds of the GMI are obtained. Impacts of dithering and imperfect channel
state information (CSI) are also investigated, and it is shown that dithering
can remarkably improve the system performance while imperfect CSI only
introduces a marginal rate loss. Finally, the analytical framework is applied
to the multi-user access scenario. Numerical results demonstrate that the
mixed-ADC architecture with a relatively small number of high-resolution ADCs
is able to achieve a large fraction of the channel capacity of conventional
architecture, while reduce the energy consumption considerably even compared
with antenna selection, for both single-user and multi-user scenarios.
