UAV-enabled Multi-pair Massive MIMO-NOMA Relay Systems with Low-Resolution ADCs/DACs

In this paper, we consider an unmanned aerial vehicle (UAV)-enabled massive multiple-input multiple-out (MIMO) non-orthogonal multiple access (NOMA) full-duplex (FD) two-way relay (TWR) system with low-resolution analog-to-digital converters/digital-to-analog converters (ADCs/DACs) architecture. Minimum mean-square error (MMSE) channel estimator and maximum ratio combining/maximum ratio transmission (MRC/MRT) at the UAV are utilized to obtain the UAV-GUs channel state information (CSI) and process the signals of multi-pair ground user (GUs), respectively. By adopting the additive quantization noise model (AQNM), the approximate sum spectrum/energy efficiency (SE/EE) with imperfect CSI and imperfect successive interference cancellation (SIC) are derived. To evaluate the effects of the parameters on system performance, the asymptotic analysis is presented. Then, the power scaling laws are provided to characterize the asymptotic performance. The numerical results verify the accuracy of theoretical analysis and show that the interference and noise can be effectively eliminated by deploying large-scale antennas, lager Rician factors, and applying proper power scaling law. We also find that the proposed system can obtain better SE performance by adjusting the height of the UAV. Moreover, the performance of the proposed system is related to the ADCs/DACs quantization bits, where the SE saturate values increase with the increasing number of quantization bits, while the EE first increases and then decreases. Finally, the SE/EE trade-off of this low-resolution ADC/DAC quantized system can be achieved by choosing the appropriate number of quantized bits, and the trade-off region grows as Rician factor increases.