I. Introduction
Yet the field trials and standard development for the 5th generation (5G) wireless communication systems are still undergoing, rapidly increasing interests have been gained in the related techniques from both academia and industry [1]–[6]. Among them, massive multiple-input multiple-output (MIMO) and millimeter wave communications, have been two promising candidate techniques [1]–[3], [7]–[9]. In massive MIMO systems, a large-scale antennas array will be deployed at the base station. As a result, the remarkable spacial diversity and multiplexing gain is achieved. This gain leads to the significantly improved system spectrum and energy efficiency by orders of magnitudes over single antenna systems [7], [8].