Towards energy-efficient massive MIMO-NOMA systems with sigma–delta ADCs and group SIC detection

This paper investigates a massive MIMO-NOMA system in which the base station (BS) employs a large antenna array with low-resolution (1-2-bit) spatial Sigma-Delta (ΣΔ) ADCs to shape and suppress quantization noise. A linear minimum mean-squared error (LMMSE) estimator based on the Bussgang decomposition is developed to accurately acquire CSI under quantization. We derive asymptotic spectral efficiency (SE) expressions for group successive interference cancellation (GSIC) receivers over Rician and general fading channels, and establish a unified framework to compare linear, SIC, and GSIC detection schemes. Results show that, with GSIC receivers, transmitting power can be scaled inversely with the number of antennas, and system performance strongly depends on group size, ADC resolution, and antenna count. A low-complexity power-allocation scheme is proposed to satisfy quality-of-service (QoS) constraints with minimal transmitted power. Simulations confirm that 2-bit ΣΔ ADCs combined with MRC-GSIC receivers and a small number of groups achieve excellent SE and energy efficiency (EE), with negligible loss compared to full-resolution systems.