Energy-Efficient MU-Massive-MIMO Hybrid Precoder Design: Low-Resolution Phase Shifters and Digital-to-Analog Converters for 2D Antenna Array Structures

This paper investigates a multi-user massive multiple-input multiple-output (MU-mMIMO) hybrid precoding (HP) scheme using low-resolution phase shifters (PSs) and digital-to-analog converters (DACs). The proposed HP approach involves two stages: RF beamforming based on the slowly time-varying channel second-order correlation matrix, baseband MU instantaneous effective to mitigate MU-interference by regularized zero-forcing (RZF) technique. We consider three design architectures: (i) full-resolution PSs DACs, with transfer block for constant-modulus beamformer, (ii) b-bit an orthogonal matching pursuit (OMP) algorithm that can optimal unconstrained (iii) q-bit taking into account also DAC quantization noise. Illustrative results show schemes sum-rate of only 2-bit PSs, while offering higher energy efficiency. Furthermore, study various PS levels reveals achieve near-optimal performance 5-bit DACs. Moreover, comparison different array configurations, namely, uniform linear (ULA), circular (UCA), rectangular (URA), concentric (CCA), indicates URA CCA outperform UCA ULA in terms spectral efficiencies.