Performance of cell-free massive MIMO with group SIC detectors and low-resolution ADCs over spatially correlated channels

Abstract

This paper considers the performance of an uplink cell-free massive multiple-input multiple-output (mMIMO) system using low-resolution analog-to-digital converters (ADCs) under spatially correlated Rayleigh fading channels. Taking the advantage of the spectral efficiency (SE), we consider zero-forcing (ZF) group successive interference cancellation (GSIC) detectors to a cell-free mMIMO system and treat the system with ZF and ZF-SIC detectors as special cases. Using the additive quantization noise model (AQNM), we analyze the achievable SE under both perfect and imperfect channel state information (CSI) and compare these results with systems employing high-resolution ADCs. Then, we derive closed form expressions of SE for the cell-free mMIMO system. Numerical results verify the tightness of approximation expressions, and the SE of the system with GSIC detectors can be further improved with an increased number of groups. To investigate the potential of low-resolution ADC architectures, we also study the energy efficiency (EE) of the system. Our findings indicate that employing SIC detectors significantly enhances EE relative to systems utilizing linear ZF detectors. Besides, a similar EE of the system employing SIC detectors can be achieved by the system with GSIC detectors.