Abstract6.1 Introduction6.2 Preparatory Work6.3 Compressive Sensing (CS)-Based Channel Estimation Schemes6.4 Channel Estimation With One-Bit ADCs at the Receiver6.5 Parametric Channel Estimation Schemes for mmWave Massive MIMO Systems6.6 Subspace Estimation and Decomposition (SED)-Based Channel Estimation6.7 Other Channel Estimation Schemes6.8 Summary