Energy Efficiency Comparison of Digital and Hybrid Precoding in 1-Bit mmWave Massive MIMO.

Millimeter wave (mmWave) massive multiple-input-multiple-output (mMIMO) is a key technology for high capacity mobile communications. The straightforward implementation of mMIMO with fully digital precoding (FDP) and high resolution digital-to-analog converters (DACs) ends up with poor energy efficiency (EE) at the transmitter. Use of 1-bit DACs is a promising approach to improve the EE, since the power amplifiers (PAs) are driven with the maximum efficiency when they are fed with constant envelope (CE) signals. In this paper, we evaluate spectral efficiency (SE) and EE performances of FDP and hybrid precoding (HP) in mmWave mMIMO downlink to identify the more compatible option with the 1-bit quantization. Numerical results illustrate that FDP in general achieves higher SE and has higher EE at high signal-to-noise ratio (SNR), whereas HP has higher EE and achieves higher maximum EE at low SNR.