  In future high-capacity wireless systems based on mmWave or massive multiple
input multiple output (MIMO), the power consumption of receiver Analog to
Digital Converters (ADC) is a concern. Although hybrid or analog systems with
fewer ADCs have been proposed, fully digital receivers with many lower
resolution ADCs (and lower power) may be a more versatile solution. In this
paper, focusing on an uplink scenario, we propose to take the optimization of
ADC resolution one step further by enabling variable resolutions in the ADCs
that sample the signal received at each antenna. This allows to give more bits
to the antennas that capture the strongest incoming signal and fewer bits to
the antennas that capture little signal energy and mostly noise. Simulation
results show that, depending on the unquantized link SNR, a power saving in the
order of 20-80% can be obtained by our variable resolution proposal in
comparison with a reference fully digital receiver with a fixed low number of
bits in all its ADCs.
