  The low-resolution analog-to-digital convertor (ADC) is a promising solution
to significantly reduce the power consumption of radio frequency circuits in
massive multiple-input multiple-output (MIMO) systems. In this letter, we
investigate the uplink spectral efficiency (SE) of massive MIMO systems with
low-resolution ADCs over Rician fading channels, where both perfect and
imperfect channel state information are considered. By modeling the
quantization noise of low-resolution ADCs as an additive quantization noise, we
derive tractable and exact approximation expressions of the uplink SE of
massive MIMO with the typical maximal-ratio combining (MRC) receivers. We also
analyze the impact of the ADC resolution, the Rician $K$-factor, and the number
of antennas on the uplink SE. Our derived results reveal that the use of
low-cost and low-resolution ADCs can still achieve satisfying SE in massive
MIMO systems.
