  In this letter, we derive an approximate analytical expression for the uplink
achievable rate of a massive multi-input multi-output (MIMO) antenna system
when finite precision analog-digital converters (ADCs) and the common maximal
ratio combining technique are used at the receivers. To obtain this expression,
we treat quantization noise as an additive quantization noise model.
Considering the obtained expression, we show that low-resolution ADCs lead to a
decrease in the achievable rate but the performance loss can be compensated by
increasing the number of receiving antennas. In addition, we investigate the
relation between the number of antennas and the ADC resolution, as well as the
power-scaling law. These discussions support the feasibility of equipping
highly economical ADCs with low resolution in practical massive MIMO systems.
