I. Introduction
Today’s telecommunication networks contribute to 2% of the total carbon dioxide emissions [1], [2]. The radio access network contributes about 92% of the total power consumption [3], [4]. Studies show that 5G base stations require about three times the power of 4G base stations [3]. One of the 5G standards’ goals is to improve the overall network energy efficiency (EE). The 5G standards have set a goal of 100 improvement in network EE compared to the existing 4G-LTE networks [5]. Massive Multiple-Input Multiple-Output (Ma-MIMO) technology is considered both at sub-6Ghz and millimeter wave (mmWave) frequencies. In both scenarios, a large number of antennas help to increase the capacity of the system. Millimeter-wave Ma-MIMO is considered for the back-haul wireless interconnects between the Base Stations (BS), to achieve high throughput and spectral efficiency. However, this comes at the cost of increased power consumption, resulting in poor EE [6], [7].