Achievable rates of hybrid architectures with few-bit ADC receivers

Massive multiple-input multiple-output (MIMO) will likely be a key component of future wireless systems. This is thanks to its large multiplexing and beamforming gains which are essential for both mmWave and low frequency systems. Hybrid analog/digital architecture and receivers with low-resolution analog-to-digital converters (ADCs) are two solutions that were proposed to reduce the cost and power consumption. The work done so far on these two architectures, though, represent two extreme cases in which either small number of RF chains with full-resolution ADCs or low-resolution ADC with a number of RF chains equal to the number of antennas is assumed. In this paper, the generalized hybrid architecture with a small number of RF chains and arbitrary resolution ADCs is considered. For this architecture, the spectral efficiency is analyzed and the achievable rates with channel inversion and SVD based transmission methods are derived. The achievable rate is comparable to that achieved by full-precision ADC receiver at low and medium SNR.